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Old 04-10-2014, 03:10 PM   #1
G.M.
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Default Vapor lock 1 and 2

There are two areas that causes vapor lock in our old Fords. I have done several years of research and found #1 the carb boiling is easy to pretty much eliminate with a 1/2" thick ventilated spacer between the intake manifold and the carb. Bob showman makes a high quality one that worked on the cars I installed them on. Gadgiteer@aol.com or 1-610-933-6637.

VL #2 is the other problem. This causes the engine to start starving for gas in warm weather when the fuel pump temperature gets to about 135 degrees. This occurs below 55 MPH. Above 55 mph more gas is flowing through the pump and cools the pump to where there is no VL. Get below 55 and into town with a few stop lights and stop signs at very slow speed and the engine cuts of. The fuel pump needs to be cooled to get restarted.

I just finished putting a simple 3/16" steel brake line fuel return from after the fuel pump back to the filler neck in my 39. I have a fuel pressure gauge in the pump to carb line after a "T" with a needle valve from where the return line runs right after the pump. I can look in the filler neck and see the fuel returning. I can also watch the pressure gauge and see the effect of pressure to the carb as I open the needle valve returning more fuel. It looks like I want to see about 1/2 lb of pressure drop to the carb to get about the amount of return fuel I THINK I need.
Two considerations, first enough fuel at 75 MPH and second enough fuel returned to cool the pump without starving the engine. I only need a little more fuel returned than the extra fuel used between 55 and 75 MPH. I have about a 1/2 tank of the old type fuel in the tank which I have to run out before filling up with the new stuff. I know this will work and I will stick my neck out and say I can tell if it works by the outside temperature of the pump. The pump on this car runs at 135 when it's hot out and the engine gets to 180, this is about where VL starts below 55 MPH. I'm pretty sure from all the testing I have done that the pump will run down in the 125 range which is below the boiling point of the new gas.
I can tell even with the old type gas by the temperature of the pump if it's going to solve the problem with the new gas. It's going to be 85 tomorrow so we will take it for the same 30 mile run for lunch we did all the other tests on. I have a few pictures I will post over the weekend. G.M.
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Old 04-10-2014, 03:21 PM   #2
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Default Re: Vapor lock 1 and 2

George, Show us the gage/needle valve setup please?
And question here: With the original 1/4" fuel line going in, isn't a 3/16" return line overkill? Is it even possible to open the needle valve all the way with the return so large? Or is your setup strictly for testing at the moment?
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Old 04-10-2014, 07:43 PM   #3
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Default Re: Vapor lock 1 and 2

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George, Show us the gage/needle valve setup please?
And question here: With the original 1/4" fuel line going in, isn't a 3/16" return line overkill? Is it even possible to open the needle valve all the way with the return so large? Or is your setup strictly for testing at the moment?
The steel brake tubing is 3/16" OD. I didn't measure the ID but it isn't much over 1/8" It takes about 14' so I wouldn't want anything smaller for the first test. I'm not going to change it, besides you can't support the return line very easy. The needle valve sticks out towards the wire cover below the voltage regulator. So there is about 8"s of tube heading over to upper left corner of the cover with a try wrap around the wire bundle that go's across the firewall. The tube bends down at that point and over with the fuel line. There is a screw just below there holding the wire cover on. I'll make a nice little tube bracket secured by that screw. I ran it back tie wrapped to the fuel line, between the double frame rails up over the wheel through a small hole in the bottom corner of the rear cross member coming out with a small lopping bend out under the rubber gas hose coupling. Tie wrapped to the vent pipe up to a 90 degree ferrule fitting with a short 1/8" pipe coupling brazed into the filler neck down about 5"s from the top. I can look in the filler neck and see the return fuel flow. I let a friend use the lift to install a new engine in his T Bird so I was on the floor and could only get one hand up to put the tie wraps on. Good finger practice putting tie wraps on with one hand. When I open the needle valve all the way open it gets down to about 1 lb pressure with a pretty good flow. I only ran it about 5 minutes in the shop. Going to take it to the car wash in the morning and as I said take it for a trial test run for lunch. I won't be able to go over 70 MPH but that should let me find out just how far I can open the valve and not starve for gas. I'll put the camera over by my shoes right now so I don't forget it. G.M.
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Old 04-11-2014, 02:48 AM   #4
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Default Re: Vapor lock 1 and 2

George, would it not be easier to insulate the fuel pump or stand like the carb insulator, you may have to lengthen the pump push rod though.
This would seem to be a better dix than the return line setup.
I will tell you later if just the carb insulator works ,as we are off away in the 33 ,about 1000miles each way towing the caravan.
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Old 04-11-2014, 07:53 AM   #5
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Default Re: Vapor lock 1 and 2

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George, would it not be easier to insulate the fuel pump or stand like the carb insulator, you may have to lengthen the pump push rod though.
This would seem to be a better dix than the return line setup.
I will tell you later if just the carb insulator works ,as we are off away in the 33 ,about 1000miles each way towing the caravan.
Lawrie
I made a 1" insulated spacer under the pump and extended an adjustable push rod to get the exact fuel pressure I wanted which is just a little over 4 lbs. As the pump warms up the pressure drops. Also a laminated aluminum and fiber glass insulation "plate" about 6x10"s under the pump. Also computer fan over the pump with an aluminum heat sink pad off the fuel pump with a thermal switch to turn the pump on. Every thing was added one at a time to see the effects of each addition. I started at the gas tank. I have dual exhaust and at the rear corners of the tank the tail pipe is within 1" of the tank and could feel the tank getting warm. I used roof flashing aluminum 12" long and bent a "U" shaped tube with 2 ears about 1 1/2" the entire length with matching holes to clamp the tube around the pipe. This really was a good heat sink and took the heat away from the tank but didn't cool the pump. These were so effective I will leave them on. Next I moved the left fuel line (duals) to make sure is was as far from the exhaust as possible and made an aluminum baffle to fit in the frame up the entire area over the wheel. Removed this yesterday. Put rubber hose over the fuel line from the frame below the firewall to the flex hose, still no improvement of heat at the pump. Put heavy foam pipe insulation over rubber hose and flex hose right up to pump, still no improvement, removed yesterday. Made the insulated plate 6x10 under the pump, removed yesterday. Made the 1" pump and long push rod. Didn't make any change but didn't remove yet. Installed the 12 volt high speed computer fan with thermal switch over the pump with a bracket off the MMO injector. This required a large 12 volt converter to run the fan. The fan did cure the gas boiling in the pump but is to bulky and expensive as a cure. Each item installed was done then tested on the SAME trip test of about 60 miles on 85 plus temperature days. Temps were taken at the start, stop for lunch again in about a 1/2 hour after lunch and after trip back at the garage.
Everything at the rear of the engine gets to at least 135 degrees, firewall, fuel line, fuel pump with no real air circulation. I even slit rubber hose 3"s long and installed on the rear edge of the hood to try and get some circulation, sill hot.
I came to the real solution from hind sight from my trip from Florida to Penna. stopping at the EVFV8 meet in Charlotte a few years ago. It was over 100 degrees on both days of the 1,200 mile trip up I-95. It ran good at the speed I traveled 65 to 75 but when I would get off for fuel and in stop and go traffic is would stall and I had to fool with or replace the pump. One time I got into stop and go traffic on I-95 due to construction and it got real slow and the engine started running ruff. I finally pulled over on the right shoulder and went past the traffic and was going to get off I-95 but in a few miles got around the problem, back up to speed and the problem went away. I tried going slow several times and the problem came back. When a certain amount of fuel is flowing through the pump the small extra amount of fuel over 55 MPH cools the pump. This amount plus a little more back through the return line should solve the problem, today we shall see??? G.M.
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Old 04-11-2014, 08:12 AM   #6
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Default Re: Vapor lock 1 and 2

G.M. Have you ever gave any thought to changing the size of the pully on the fan to speed it up to get more air flow under the hood ??
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Old 04-11-2014, 08:38 AM   #7
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Default Re: Vapor lock 1 and 2

I have done this plus 6 bladed industrial fans on generator mounted fans plus a shroud which is the best cooling with hi flow pumps you can get. BUT this is a 39 deluxe with the crankshaft mounted fan which only throws the air against the front of the block. G.M.
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Old 04-11-2014, 02:24 PM   #8
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Default Re: Vapor lock 1 and 2

Thanks to all for some very good information. I remember this a very common problem that I had on my 51 back in 1959 coming over the Siskues(sic) in Oregon I used all the cokes I had to cool the pump so had to resort to peeing into a empty coke bottle and pour on the pump to get over the mountain. Not sure what I did for long term solution perhaps a new pump and a small nut for a shim to give more stroke to the pump. Took a while to get rid of the odor of burned pee! Gary
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Old 04-11-2014, 03:11 PM   #9
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Default Re: Vapor lock 1 and 2

Good trip. First a little advise on getting in a hurry to tear things apart. On the test trip the engine was running crappy, I pulled the choke to try to clear it and finally in about 15 miles it took a gulp and started running pretty good. Gas is over a year old and smalls bad. Every time we slowed down we could smell it.
Before starting the trip I had 3 1/2 lbs fuel pressure and adjusted the return valve down to 2 1'2 lbs. After about 7 miles with running so bad I stopped to close the valve completely thinking I was returning to much fuel and starving the engine. Closing the valve didn't make any difference, still crappy. At about 15 miles what ever dirt was causing the problem went on by and it perked right up to as good as it will get until I run this bad gas out. Stopped for lunch and checked the top of the pump and it was 118 degrees, opened the return valve to about 2 1/4 lbs letting gas flow through the pump and back to the tank at an engine speed of about 20 MPH. The pump temperature started dropping and after about 2 minutes the pump cooled to 109 on the top. Stopped on the road a couple of times adjusting the valve/ to see if it would starve for fuel and didn't see any signs of starvation above 2 1/4 lbs of pressure. Keep in mind the engine wasn't running 100% with this old smelly gas. Got back to the shop, opened the hood and had 123 on the top of the pump. Opened the valve further with no change. Checked the temp on the bottom of the pump and it was 170. It was a little hotter on the return trip as the sun came out. It looks like it works just as I thought it would. Will do more tests when I get rid of the old smelly gas. Took some pictures of the return tube installation. Will post them when I figure out this new camera and load the pictures. G.M.
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Old 04-12-2014, 07:44 AM   #10
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Default Re: Vapor lock 1 and 2

Was thinking about the return fuel line and something came into my mind. It will be interesting to see if the fuel drains from the pump to carb fuel line back to the tank after sitting a while. I will find out next time I start it. IT may not effect starting if it don't drain the pump. The check valve in the pump should keep enough fuel in the tank line and the glass bowl to start. At the worst I will need a 2 lb check valve in the return line. G.M.
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Old 04-12-2014, 08:33 AM   #11
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Default Re: Vapor lock 1 and 2

GM, So what i understand from your trip report is that it seems to make no difference the degree open as long as there is some constant flow back to the tank? That would make sense from your previous report that below 55 mph woiuld cause intermittent operation of the pump and excess heat build up.

On the 2 lb check valve you are presently thinking about, I think that would complicate your effort with no gain. Remember, you already have a check valve in the carb, so the effect would be to allow heat soak pressure in the pump to carb line that may overcome the carb check valve before the line check valve, not good.
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Old 04-12-2014, 10:13 AM   #12
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Default Re: Vapor lock 1 and 2

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GM, So what i understand from your trip report is that it seems to make no difference the degree open as long as there is some constant flow back to the tank? That would make sense from your previous report that below 55 mph woiuld cause intermittent operation of the pump and excess heat build up.

I can't pin down the exact amount of fuel that can be returned without starving for fuel on one test run, Also I'm going to have to run the old nasty smelling fuel out to get a true feeling of when there is not enough fuel at 65 to 70 MPH. The excessive fuel being returned is what will cool the pump. This was evident at the lunch stop with no fuel being returned and the temp on the top of the pump was 118 and I opened the return and the temp dropped to 109.

On the 2 lb check valve you are presently thinking about, I think that would complicate your effort with no gain. Remember, you already have a check valve in the carb, so the effect would be to allow heat soak pressure in the pump to carb line that may overcome the carb check valve before the line check valve, not good.
There is no check valve in the carb. If your referring to the needle valve if it's closed it would prevent drain back through the return line. If it is open it allows air to enter the pump to carb line and the return line letting fuel drain back through the return line. An exact check valve at 2 1/2 lbs could eliminate the needle valve. But if the check valve is not on the money at 2 1/2 lbs the return flow changes. A lower check valve at say 2 lbs would allow full return flow if desired but prevent drain back after shut down. We are getting into "what if's" and that's not my game. I am set up to get real life results. This where it takes time and patience to find the true answers. G.M.
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Old 04-12-2014, 11:03 AM   #13
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Default Re: Vapor lock 1 and 2

Forgive my nay-say comment but back in the mid 50s I drove my standard fuel set up 1951 ford all over Texas in over 100 deg. weather with no "vapor lock" problems. Also back and forth to Ohio a couple of times. If there is, in fact, vapor lock problems occurring now, then it must be in the formula of the fuel nowadays.
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Old 04-12-2014, 03:00 PM   #14
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Default Re: Vapor lock 1 and 2

The problem is with this new 10% ethanol fuel it starts to boil in the fuel pump in the 130 to 135 range. On a warm day after running awhile every thing in the area at the rear of a 39 deluxe engine gets over 135 degrees. It also boils over in the carb mostly after shut down. This can be corrected with a 1/2" vented insulator under the carb. The pump boiling is more difficult to over come. It looks like I may have finally have a sure solution but it requires installing a return line which a lot of people won't want to do. I never had any problems either until this stuff came along. We can get the old type fuel locally without ethanol but if you go on a trip who wants to search for it. I have 3/8's of tank of smelly old fuel to burn out before I can refill with new ethanol. Then I can do some tests when it's above 85 outside and get definite answers. G.M.
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Old 04-12-2014, 09:13 PM   #15
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Default Re: Vapor lock 1 and 2

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...An exact check valve at 2 1/2 lbs could eliminate the needle valve. ... G.M.
Hold on here. The carb is looking for the correct float level in the bowl. A pressure based check valve will not satisfy that need, only the float controlled needle valve can do that.

So... let the return line drain back to the tank if the float opens the needle valve. No problemo with that, is there? Why allow a pressure buildup in the line after shut down anyway?
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Old 04-12-2014, 10:48 PM   #16
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Default Re: Vapor lock 1 and 2

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Hold on here. The carb is looking for the correct float level in the bowl. A pressure based check valve will not satisfy that need, only the float controlled needle valve can do that.

Check valve is in the return line not the pump to carb line.

So... let the return line drain back to the tank if the float opens the needle valve. No problemo with that, is there? Why allow a pressure buildup in the line after shut down anyway?
There's no problem letting the return line draining back but you don't want the pump and the pump to carb line draining every time it shuts down. There is no pressure build up in a stock set up. Stock, pump pressure remains in the carb line and slowly drops to zero in several minutes. G.M.
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Old 04-13-2014, 12:03 AM   #17
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Default Re: Vapor lock 1 and 2

You said a 2 1/2 lb check valve could eliminate the needle valve. No way.
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Old 04-13-2014, 06:42 AM   #18
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You said a 2 1/2 lb check valve could eliminate the needle valve. No way.
YES WAY. Figure it out. G.M.
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Old 04-13-2014, 07:04 PM   #19
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Default Re: Vapor lock 1 and 2

"The pump boiling is more difficult to over come. It looks like I may have finally have a sure solution but it requires installing a return line which a lot of people won't want to do. I never had any problems either until this stuff came along."

GM - I think you are on the right track with your fuel return VL2 theory.

I ran into a similar vapor lock condition with a hi-performance engine. The original fuel delivery system was set up to deliver 6-13 psi thru a boost referenced fuel regulator near the carb. Under load with all the engine heat the engine would periodically starve for fuel and quit. After much head scratching, some research, and tinkering I discovered that "deadheading" the fuel delivery at the carb created a situation where the heat buildup in the fuel delivery process caused the fuel to vaporize somewhere between the fuel pump, the fuel regulator and the carb. I added a fuel return line from the fuel pressure regulator to the tank and haven't had any vapor lock issues since then. I think that providing a fuel return system that allows the fuel to bypass a "deadhead" condition where a heat sink such as a fuel pressure regulator or an engine mounted fuel pump could cause vaporization will deal with the VL2 gremlin.
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Old 04-13-2014, 08:07 PM   #20
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Default Re: Vapor lock 1 and 2

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YES WAY. Figure it out. G.M.
No, you figure it out. Explain how a pressure check valve will maintain the correct fuel level in the float bowl, please? Do away with the needle valve and float? The float operates the needle, both are required.
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Old 04-13-2014, 08:45 PM   #21
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No, you figure it out. Explain how a pressure check valve will maintain the correct fuel level in the float bowl, please? Do away with the needle valve and float? The float operates the needle, both are required.
Go back and read my posts, your confused. G.M.
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Old 04-13-2014, 10:04 PM   #22
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Default Re: Vapor lock 1 and 2

In 1957 GMC buses used this same idea in a rear engine bus, had a 248 six with hydramatic would idle on hot days no problem. They had a tee fitting at the carb with return line to tank, used mechanical pump on side of engine. same idea, the tee had a calibrated hole for bypass. This engine was in sideways so no forced air. The plan should work! Laurie
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Old 04-13-2014, 10:28 PM   #23
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Default Re: Vapor lock 1 and 2

George, I have seen in HQ holden 6 fuel pumps,(these are much the same as the flatheads) there was a real small hole in the top that went between the suction and delivery sides,this was I assume to vent the fuel pressure when the motor was stopped and heat soak got into the pump,these engine also used a stormier carb. Just a thought
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Old 04-13-2014, 10:35 PM   #24
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Default Re: Vapor lock 1 and 2

George, here we go again. You write something then you forget what you wrote and deny it forever, but then of course everyone is confused but you. Go back and read your own post right here on this thread.

Oh by the way, George, you be sure to take full credit for inventing that fuel return line now, here?
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Old 04-13-2014, 10:57 PM   #25
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Old 04-14-2014, 12:16 AM   #26
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Default Re: Vapor lock 1 and 2

I like the idea of this. It seems like this is the way things are going(or have been but I am out of touch with modern fuel systems) with a return line . I know they are doing this with Holley carbs on high perf engines and of course mechanical fuel injection .
I have a question going back to what I know about how a mechanical fuel injection fuel system works with a mechanical pump that gains pressure with RPM's and has a return line back to the tank to bleed off excess pressure .
So with that said ,How much pressure can the needle & seat handle safely on a Stromberg 97 ??
Lets say it will handle 3 lbs safely , could you get a stock pump to put out 4lbs cold and maybe 3 1/2 lbs hot , then run a return line off the fuel line between the pump and carb/carbs that has a 2 1/2 lb check valve/poppet with a pill (restricting jet ) in it set at .oXX" (would have to do the math) so essentially giving the carb/carbs 2 1/2 lbs at all times with fuel also returning back to the tank to keep the fuel pump cool ???
I am sure there are flaws with this thought but I am liking what you are doing .
I really like the tuning/tinkering/learning/researching part of playing with old Fords in today's modern surroundings. Never a dull moment .
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Old 04-14-2014, 12:48 AM   #27
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Default Re: Vapor lock 1 and 2

Mike, I think you may be somewhat in agreement with GM's check valve theory, so I'll try to blow that theory apart right here.

The pressure required from the pump is simply to be sufficient to replenish the float bowl when the needle valve opens, and to be incapable of blowing past that valve when it closes. The carburetor wants no pressure value beyond that stated.

Adjustment of the bowl level is accomplished with the float, not anything to do with pressure. It is the fully vented float bowl level that is important, to provide a gravity feed to the main jets, no pressure, just gravity.
Beyond that, a check valve is not called for as the needle valve is sufficient to perform its function without the added complication of a check valve.
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Old 04-14-2014, 01:22 AM   #28
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Default Re: Vapor lock 1 and 2

Surely if you remove the needle valve and use a check valve set at 2 1/2lb or whatever pressure, the float bowl will just overflow and you'd have fuel going allover the place. With out the needle being closed by the float, what is going to stop the fuel at the correct level?
GM, could you please explain this? I've tried to understand your thinking here, but I can't get the check valve bit.
I'm a real believer in the return line from the pump to cool the pump, it's been used on production carburetor engines since late 60's or early 70's wether it be a calibrated hole in a 'T' fitting twix pump and carb or an extra small barn on the pump or return from pressure regulator.
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Old 04-14-2014, 02:47 AM   #29
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I like the idea of this. It seems like this is the way things are going(or have been but I am out of touch with modern fuel systems) with a return line . I know they are doing this with Holley carbs on high perf engines and of course mechanical fuel injection .
I have a question going back to what I know about how a mechanical fuel injection fuel system works with a mechanical pump that gains pressure with RPM's and has a return line back to the tank to bleed off excess pressure .
So with that said ,How much pressure can the needle & seat handle safely on a Stromberg 97 ??
Lets say it will handle 3 lbs safely , could you get a stock pump to put out 4lbs cold and maybe 3 1/2 lbs hot , then run a return line off the fuel line between the pump and carb/carbs that has a 2 1/2 lb check valve/poppet with a pill (restricting jet ) in it set at .oXX" (would have to do the math) so essentially giving the carb/carbs 2 1/2 lbs at all times with fuel also returning back to the tank to keep the fuel pump cool ???
I am sure there are flaws with this thought but I am liking what you are doing .
I really like the tuning/tinkering/learning/researching part of playing with old Fords in today's modern surroundings. Never a dull moment .
Mike
Aeromotive makes a decent fuel pressure regulator 3-60 psi with a by pass port that you can plug a fuel return line into. Cost $135.00. No need to reinvent the wheel if you decide to install a fuel return line. These regulators are designed to be used on high performance engines which may be overkill on our street driven flatheads, but its use along with a fuel return line might be worth the effort if vapor lock becomes a serious problem. Les Williams
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Old 04-14-2014, 04:59 AM   #30
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Default Re: Vapor lock 1 and 2

Well mine will be a little hard to start after you let it sit for 15 min after riding around for 10 miles or so and you have to grind and when it fires it like it is rich and loaded up.Went and put reg gas without 10% in it and really made no difference.Did the same thing after that run.But shut it off and wait a minute or so and it fires before it turns over 1 rev.Have 1"micarter(spell) under the 2 97's.Electric pump only at 2 1/2 lbs.This has just started in the last few months.Drive it every week all year so it doesn't sit very long unless it rains
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Old 04-14-2014, 08:41 AM   #31
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Well mine will be a little hard to start after you let it sit for 15 min after riding around for 10 miles or so and you have to grind and when it fires it like it is rich and loaded up.Went and put reg gas without 10% in it and really made no difference.

You have hit the nail right on the head. Although the return line may help avoid vapor lock while the engine is running, that is not the most frequent problem with vapor lock. It is after a hot engine has sat out in the sun for 10 minutes. The return line has no benefit then, neither does a carb spacer. The engine heat and the sun beating down on the hood just heats everything, including the carb, fuel lines, and fuel pump, above boiling temperature and you have vapor lock no matter how many return lines or spacers you have. I was actually going to install a return line and bought all of the materials to do so until I figured this out. The only solution to this problem is to either open the hood every time you stop, install a fan that comes on when the engine is turned off to blow air from outside the engine compartment into it to cool it, or install an electric fuel pump to prime everything and refill the carburetor that has boiled out like I did.
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Old 04-14-2014, 08:49 AM   #32
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You have hit the nail right on the head. Although the return line may help avoid vapor lock while the engine is running, that is not the most frequent problem with vapor lock. It is after a hot engine has sat out in the sun for 10 minutes. The return line has no benefit then, neither does a carb spacer. The engine heat and the sun beating down on the hood just heats everything, including the carb, fuel lines, and fuel pump, above boiling temperature and you have vapor lock no matter how many return lines or spacers you have. I was actually going to install a return line and bought all of the materials to do so until I figured this out. The
only solution to this problem is to either open the hood every time you stop, install a fan that comes on when the engine is turned off to blow air from outside the engine compartment into it to cool it, or install an electric fuel pump to prime everything and refill the carburetor that has boiled out like I did.

Henry:

How long have you been around these cars , & use those two words together may be a foopaa !!!!!
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Old 04-14-2014, 09:48 AM   #33
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Henry:

How long have you been around these cars , & use those two words together may be a foopaa !!!!!
Had to look up "foopa".* Hadn't seen that before. You are right on there. I certainly do have some of that.

*foopa
"An area of fat usually found on the bellies of older women who do not exercise, it can also be found rarely in some men and younger women who don't get exercise. It is located above the hip and is located dead center of the body usually above waistline, making one appear to be bloated or enormously fat."

(I'm thinking your use of "foopa" may have been a faux pas.)
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Old 04-14-2014, 10:13 AM   #34
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Had to look up "foopa".* Hadn't seen that before. You are right on there. I certainly do have some of that.

*foopa
"An area of fat usually found on the bellies of older women who do not exercise, it can also be found rarely in some men and younger women who don't get exercise. It is located above the hip and is located dead center of the body usually above waistline, making one appear to be bloated or enormously fat."



(I'm thinking your use of "foopa" may have been a fopaux.)
Faux pas

And, when said person is wearing tight pants and a tight shirt, these now visible fat pockets are called "muffin tops".
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Old 04-14-2014, 10:41 AM   #35
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Default Re: Vapor lock 1 and 2

Nobody is talking about removing the needle and seat . I am not sure where this got derailed but that has never been said by GM or myself.
All that this discussion is about is keeping fuel flowing through the fuel pump at all times to keep it cooler while still having at least 2- 2 1/2lbs of pressure at the carb/carbs to keep them from starving at higher RPM's.
That's it .

Old Henry : question for you : If the under hood temps are a concern then wouldn't it be to our advantage to start with the carb/carbs cooler ( with the spacers) and the fuel pump cooler ( with a return line ) ????
So instead of shutting off the engine with a fuel pump at 135 deg and then it rising to lets say 8 deg , we would start with a fuel pump at 125 deg and then it will rise the same 8 deg so ending up at 133 deg which is still under what GM proved to be the vapor lock point under the hood of his 39 Deluxe .
In theory that would solve the vapor lock for restarting the car in hot weather.

(My numbers are all just examples to explain what I am saying except GM's 135 deg that was proven in his situation )
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Old 04-14-2014, 10:56 AM   #36
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Old Henry : question for you : If the under hood temps are a concern then wouldn't it be to our advantage to start with the carb/carbs cooler ( with the spacers) and the fuel pump cooler ( with a return line ) ????
So instead of shutting off the engine with a fuel pump at 135 deg and then it rising to lets say 8 deg , we would start with a fuel pump at 125 deg and then it will rise the same 8 deg so ending up at 133 deg which is still under what GM proved to be the vapor lock point under the hood of his 39 Deluxe .
In theory that would solve the vapor lock for restarting the car in hot weather.

(My numbers are all just examples to explain what I am saying except GM's 135 deg that was proven in his situation )
You might be right but I highly doubt it. You're talking about less than 6 oz of cooler fuel in the carb, pump, and fuel lines against 600 lbs of steel that's 180-190. I don't think it would take long to melt 6 oz. of frozen water under that hood sitting out in the sun in 10-15 minutes much less heat that much fuel from 125 to above boiling temperature under the same circumstances. Just my thoughts.
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Old 04-14-2014, 10:59 AM   #37
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Nobody is talking about removing the needle and seat . I am not sure where this got derailed but that has never been said by GM or myself.
G.M.'s statement in post #12: "An exact check valve at 2 1/2 lbs could eliminate the needle valve."

That's what the discussion has been trying to "debunk".
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Old 04-14-2014, 11:04 AM   #38
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Faux pas

And, when said person is wearing tight pants and a tight shirt, these now visible fat pockets are called "muffin tops".
Not sure where you got that definition. From Wikipedia: A faux pas (/ˌfˈpɑː/ plural: faux pas /ˌfˈpɑːz/) is a socially awkward or tactless act, especially one that violates accepted social norms, standard customs, or the rules of etiquette.[

I think that's the word Bill and I were meaning to use. Unfortunately, we're both spelling challenged.
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Old 04-14-2014, 11:34 AM   #39
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Default Re: Vapor lock 1 and 2

I remember having to put a wet rag on pump coming back from Jersey shore in the 50's in my 46 Ford tudor it would dry out and we might have to rewet it in the ditch on roadside n WOW to be that young again
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Old 04-14-2014, 11:42 AM   #40
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Default Re: Vapor lock 1 and 2

The NEEDLE VALVE is being used to trim the by-pass pressure, NOT to be confused with NEEDLE and SEAT...two, distinctly-different animals. DD
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Old 04-14-2014, 11:47 AM   #41
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Old Henry, the way I am reading post 12 is GM is using that statement as an example and further down he states these are "what ifs" . No where does he say removing the needle/seat is what he is trying to do.At least that is the way I am reading it
And this is what we call "the internet" folks
Things read can be interpreted many different ways . That is why these discussions are tough to have via the net. I do enjoy them though. It's fun bouncing ideas and thoughts back and forth.
In my opinion GM is giving us facts as per what he is doing on his car. I personally am intrigued by the idea. There are a lot of variables but I for one am interested in his findings.
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Old 04-14-2014, 11:49 AM   #42
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V8Coopman, I totally agree. Very well said !
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Old 04-14-2014, 12:05 PM   #43
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The NEEDLE VALVE is being used to trim the by-pass pressure, NOT to be confused with NEEDLE and SEAT...two, distinctly-different animals. DD
OK now! That concept is clear to me now. Why couldn't GM have explained himself better? His only reference was to eliminate the needle valve with the pressure valve. Now we're talking about eliminating a manually operated needle valve for the return, not the float operated needle valve for the bowl. Old Henry's Einstein post applies here!
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Old 04-14-2014, 12:13 PM   #44
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Default Re: Vapor lock 1 and 2

I just read what GM said...explained himself fairly well. Clear as mud to me. DD
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Old 04-14-2014, 03:37 PM   #45
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Default Re: Vapor lock 1 and 2

A simple "I'm talking about the needle valve used to calibrate the returned amount of fuel, not the needle for the float" would have saved all this fun.
Now that ambiguity is cleared up, I understand the thinking.
Thank you.
Martin.
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Old 04-14-2014, 04:28 PM   #46
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Default Re: Vapor lock 1 and 2

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The NEEDLE VALVE is being used to trim the by-pass pressure, NOT to be confused with NEEDLE and SEAT...two, distinctly-different animals. DD
You got it DD Besides I don't use needle valves in my 97 carb. I use the double ball valve provided by Uncle Max. These give a smoother fuel delivery to the fuel bowl. You can run the 97 with the top off and watch the level of fuel in the bowl. The balls deliver minute amounts of fuel all the time when fuel is entering the bowl. The fuel level never varies much. Most needle valves stick before moving and the level varies a 1/2". I have used these for 30 years and never had a problem with them. Prior to that I had carb flooding or no fuel problems. G.M.




These are the "spurious parts" removed
that I used to isolate the VL problem.
SP was Henry's words.
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Old 04-14-2014, 06:54 PM   #47
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I bite the bullet and drained the nasty gas and replaced it with 10 gallons of 10% ethanol. Engine started this morning with 1 revolution with the starter. Pump was at 4 lbs and adjusted the pressure to the carb using the adjustable needle valve in the return line to 2 3/4 lbs. The more flow through the return line the less pressure in the carb line. Even with the valve all the way open there will still be enough restriction in the return to maintain some pressure to the carb. If I had say a 3/8" fuel line I think I could dump enough fuel that the engine would stall. This is provided the valve and all fittings had a 3/8" hole through them. The fuel will take the path of least resistance.
With the fuel set at 2 3/4 lbs we made the 30 mile run for lunch, engine ran perfect all the way. I dropped down to 12 MPH as I made a turn and it pulled out nice and steady only to think latter it was in Columbia. Stopped for lunch measured the top temp on the fuel pump which was 122, opened the valve a few turns and the temp dropped to 110. This proves again the return fuel cools the pump. Not really, the extra flow of fuel through the pump is what cools it. I haven't opened the needle valve all the way and drove the car yet. I want to do this and see how it runs at top speed and what the carb line pressure is. After lunch it took 5 or 6 turns of the engine to fire. This is unusual, it usually fires on the first turn. Stopped 2 more times for 10 minutes each time and had the same starting results. Next time I stop I will turn the needle valve off at the same time I shut the engine down and see how it starts after 10 minutes. This could be a drain back through the return line problem. If so a 1 lb check valve at the adjustable needle valve will solve this. It was only 85 degrees today and the engine ran at 180 all the time with Bob Shewmans 180 stats in the hoses. I need temperatures up near 100 now and get in city traffic for the real test. I'm satisfied from what I have seen there will be no VL problem. G.M.

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Old 04-15-2014, 01:43 AM   #48
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Default Re: Vapor lock 1 and 2

I've looked into the use of a return line for the fuel line. My thinking wasn't born from pump temp or vapour lock. Only because I've been lucky enough to have never had it. My thinking was born off multi carb setups. I feel that when using a electric pump with enough flow for high performance use, the regulator is wound down (pressure wise) so much that I'm sure it hinders flow at high demand. Really don't want a lean out situation with my foot to the floor.
I feel I could have my cake and eat it with a return line setup,
Thoughts on this?
many thanks
Martin.
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Old 04-15-2014, 05:09 AM   #49
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Default Re: Vapor lock 1 and 2

That is the way mine just started doing after cranking first with almost 1 spin of engine and then run it shut it down for 20 minutes or so crank for seems like 5-10 rounds before fires and seems to be on the flooded side but it is only with electric pump.Just started this this year.before 1 turn of motor and doing the fires up.I guess I will have to live with it.But my Farmall Cub started doing the same thing and just rebuilt carb so I see if it fixed it.I hate this crappy gas nowdays
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Old 04-15-2014, 06:50 AM   #50
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That is the way mine just started doing after cranking first with almost 1 spin of engine and then run it shut it down for 20 minutes or so crank for seems like 5-10 rounds before fires and seems to be on the flooded side but it is only with electric pump.Just started this this year.before 1 turn of motor and doing the fires up.I guess I will have to live with it.But my Farmall Cub started doing the same thing and just rebuilt carb so I see if it fixed it.I hate this crappy gas nowdays
It's hard tell if this condition is pumping fuel or lose of fuel in the carb after shut down. I hadn't noticed it before the return line but I have been busy with property projects and haven't driven the 39. I have a sight glass that mounts on the carb showing the fuel level in the bowl at all times. I think I will try and find it this morning and put it on then I can tell where the problem is. G.M.
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Old 04-15-2014, 10:34 AM   #51
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Default Re: Vapor lock 1 and 2

George, a word of caution regarding the sight glass... Ford discovered that they were unreliable for indicating float level due to under hood air flow. If you can dampen the effect of the wind, it should work for you.
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Old 04-15-2014, 02:50 PM   #52
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George, a word of caution regarding the sight glass... Ford discovered that they were unreliable for indicating float level due to under hood air flow. If you can dampen the effect of the wind, it should work for you.
Not much air flow over the top of a 39 deluxe engine that's one of the main problems as described before. G.M.
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Old 04-15-2014, 02:57 PM   #53
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Default Re: Vapor lock 1 and 2

The use of a return line is an excellent idea.

I think there is some confusion in terminology in this discussion. A "check valve" is a valve that allows flow in only one direction. A "pressure relief valve" is a valve that maintains a specific pressure. You cannot set a check valve at a specific pressure, e.g. 2 1/2 psi. A pressure relief valve with a return line would work in place of the needle valve and would be an improvement IMO. expavr already mentioned that one is available.
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Old 04-15-2014, 03:01 PM   #54
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Default Re: Vapor lock 1 and 2

With all due respect, would blocking-off the stock fuel pump and running directly from an electric fuel pump with a pressure regulator eliminate the problem all together?
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Old 04-15-2014, 03:12 PM   #55
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With all due respect, would blocking-off the stock fuel pump and running directly from an electric fuel pump with a pressure regulator eliminate the problem all together?
Yes. Or, run the stock mechanical pump and only turn on the electric when vapor locked like most people do.
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Old 04-15-2014, 06:31 PM   #56
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I've looked into the use of a return line for the fuel line. My thinking wasn't born from pump temp or vapour lock. Only because I've been lucky enough to have never had it. My thinking was born off multi carb setups. I feel that when using a electric pump with enough flow for high performance use, the regulator is wound down (pressure wise) so much that I'm sure it hinders flow at high demand. Really don't want a lean out situation with my foot to the floor.
I feel I could have my cake and eat it with a return line setup,
Thoughts on this?
many thanks
Martin.
When you set up a fuel delivery system for hi performance you should be building into that system fuel flow to keep the A/F ratio in the engine at or near optimum at WOT. This starts with the electric fuel pump which is continuously pumping the fuel at whatever maximum pressure is needed for WOT. When you're not at WOT the fuel pump which continues to pressurize the fuel line at the higher pressure is adding heat and possibly air thru cavitation to the fuel due to lack of demand in the carb. The fuel flow is "deadheaded" at the regulator it can go no where but to the carb where its not needed. A fuel return line sends the uneeded fuel supply from part throttle operation back to the tank where it blends with the cooler fuel in the tank. I came to this conclusion after several bouts of what I think was VL2 fuel starvation on a supercharged engine. Compare the fuel pressure your electric pump puts out versus the pressure on your fuel regulator. My guess is that you will find a big difference between the two and while some of that difference (2-3psi?) might be needed to compensate for line loss between the pump and regulator your electric fuel pump is operating well above the engine's fuel demand at part throttle.
I'm not familiar with how to setup a multiple carb system, but it would seem that if you set the fuel flow for engine demand at WOT based on whatever the carbs' design allowed the fuel delivery system should be able to maintain that fuel pressure to the carbs. Here I'm assuming that you're using a fuel log of some sort that feeds each carb. As far as leaning out at WOT this would be where the individual carb tuning would become important. I suggest raising that question on the HAMB web site.
Les
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Old 04-15-2014, 07:20 PM   #57
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Default Re: Vapor lock 1 and 2

Major vapor lock today temp near 90 here in Yuma hit the freeway and vapor locked very bad. I stoped and poured ~ 2 qts. of water over the pump restarted and drove 25 to 40 ~ 20 miles with the choke fully applied. I will do a pressure check tomorrow. After I got home I put a zip lock bag with ice and water in it over the pump and drove a bit it worked ok and beats peeing on the pump. Gary
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Old 04-16-2014, 03:32 AM   #58
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Les, thank you for your reply, that makes sence.
Martin.
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Old 04-18-2014, 01:56 PM   #59
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Default Re: Vapor lock 1 and 2

I installed a sight glass tube on the 97 to watch the fuel level in the carb. Installed the carb this morning and put a pen line on the tube where I thought the carb fuel bowl level should be. Cranked the engine over to fill the carb and the fuel level came right to the bottom of the line. Started the engine, adjusted the fuel pressure with the return line needle valve to 2 3/4 lbs going to the carb. The fuel level in the sight glass stays at the line with 2 3/4 lbs adjusted pressure in the carb line, 3 1/2 lbs full flow to the carb and no return fuel with the needle valve closed or 2 lbs with the needle valve wide open. NO change in carb fuel level with the return closed or fully open with a 3/16 OD steel brake tube return line. If it runs at 70 MPH with the return line wide open there is no need for the return line needle valve.
NOW THE INTERESTING PART.
When I shut the engine down with the needle valve even PARTIALLY open the fuel gauge drops to BELOW zero showing about 1/2 lb of vacumn on the pressure gauge immediately at shut down and the fuel in the sight glass was slightly below the line.
At shut down with the gauge showing over 3 lbs and the return line needle valve CLOSED the sight glass was just over the top of the sight glass pen line. The differences of the fuel level in these two cases are so close it doesn't matter.
The thing that matters IS the pressure gauge showing a 1/2 lb of vacumn with the return line open at shut down, this indicates fuel is syphoning back the return line drawing fuel from the carb line and fuel pump. This will make restarting after sitting say 10 minutes a little harder as I experienced, it took 4 or 5 turns of the engine to start. With the return line CLOSED I had pressure that remained in the fuel pump and line for several minutes slowly bleeding down through the fuel pump check valve as described in the Ford service bulletins.
My conclusion is IF there is sufficient fuel to run the engine continually at 70 MPH with a 3/16" OD return line FULLY OPEN which I will have to measure the ID which is the important part then NO adjustable needle valve will be required. I believe the ID will be in the .120 to .130 range. I still have to road test at 70 MPH with the return WIDE OPEN.
We still have the fuel drain back through the return line pulling the fuel from the pump and carb line when the return line is even partially OPEN after shut down. A simple 1 lb check valve in the return line will solve that problem. It won't effect the fuel return because that pressure is above the 2 + lbs we get with the valve wide open and the check valve will shut off the return when the pump stops pumping when the pressure drops to 1 lb. There will be a little fuel returned as the shut down pressure drops from it's 2 1/2 to 2 3/4 lb to 1 lb.
Supposed to get around 90 next week so I can check fuel pump temperatures with the return working but I'm sure the VL problem in the pump is gone with the return.
While the carb fuel level sight glass is on I will check the effect of heat boiling the gas out of the carb after shut down. If fuel leaves the carb bowl I will see it on the sight glass. I don't think I will see much fuel lose with Bob Shewmans 1/2" vented carb spacer being in place. Pictures to follow. G.M.
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Old 04-18-2014, 05:18 PM   #60
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Default Re: Vapor lock 1 and 2

George, your tests and analysis's are greatly appreciated. I'm sure you already know that or you wouldn't be doing them. What they do in fact is dispell or confirm long standing theories and/or myths, and provide food for thought about projects we can all do to stay on the road. I think this particular test is one of your better uses of mind power over mechanical impotence!

Now, food for thought regarding the 1 lb check valve you propose: I see no downside in its installation beyond just complicating a simple solution, but question the need for it in the first place. First, you reported that the sight glass showed no significant movement with the return line open or closed, so the reported engine spin of 4 or 5 revolutions shouldn't have been fuel related. Second, a negative pressure in the line theroetically could pull fuel into the pump as it is being sucked out, as both pump valves are forward directional. However, if the pump does in fact drain back, the fuel in the carb should be adequate to prime the pump again, wouldn't it? Perhaps these questions can be addressed at your next test run?
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Old 04-18-2014, 07:16 PM   #61
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George, your tests and analysis's are greatly appreciated. I'm sure you already know that or you wouldn't be doing them. What they do in fact is dispell or confirm long standing theories and/or myths, and provide food for thought about projects we can all do to stay on the road. I think this particular test is one of your better uses of mind power over mechanical impotence!

Now, food for thought regarding the 1 lb check valve you propose: I see no downside in its installation beyond just complicating a simple solution, but question the need for it in the first place. First, you reported that the sight glass showed no significant movement with the return line open or closed, so the reported engine spin of 4 or 5 revolutions shouldn't have been fuel related. Second, a negative pressure in the line theroetically could pull fuel into the pump as it is being sucked out, as both pump valves are forward directional. However, if the pump does in fact drain back, the fuel in the carb should be adequate to prime the pump again, wouldn't it? Perhaps these questions can be addressed at your next test run?
You are referring to the fuel in the carburetor being adequate to start the car in order to get the fuel pumping, correct?
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Old 04-18-2014, 07:43 PM   #62
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You are referring to the fuel in the carburetor being adequate to start the car in order to get the fuel pumping, correct?
yes
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Old 04-18-2014, 07:45 PM   #63
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Default Re: Vapor lock 1 and 2

old henry's souloution would have resolved gary365's problem with a momentary ON switch when the fuel boils.
i ran a small inline fuel pump full time along with the mechanical for many years in 100 degree days here in south texas and never experianced any vapor lock after its installation.
a small in line pump wheather part time or full time seems to me to be a sensable, and easy, souloution to this whole return line, computer fan blowing on the fuel pump, insulating fuel lines, pouring water on teh fuel pump, ect experimentation.
sorry to say, but with all the complex effort on this vapor lock problem, although the insulated spacer is a great idea, with a small on line pump (part time or full time) like what old henry has been advocating is a simple and quite effective souloution and simple.. worked quite well for me.
we will be living with ethenol as an additive for the forseable future. the inline pump is a simple fix......
just my thought........ don
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Old 04-18-2014, 10:10 PM   #64
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As I said before, as well as the return line may work for preventing vapor lock while running, even idling, I still don't think the return line will keep the mechanical pump from vapor locking after the car has sat in the sun on a hot day with the engine off. It will be interesting to see.
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Old 04-19-2014, 12:30 AM   #65
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George, your tests and analysis's are greatly appreciated. I'm sure you already know that or you wouldn't be doing them. What they do in fact is dispell or confirm long standing theories and/or myths, and provide food for thought about projects we can all do to stay on the road. I think this particular test is one of your better uses of mind power over mechanical impotence!

I didn't do the tests to be appreciated, or fame, I do them to solve my own personal problems with my old fords and I don't mind sharing the results which people can use if they want. This was the same purpose for the diode, coil, water pumps, 3 lb valve, center bearing, flex hose, modified 330-180 stats in the hoses and the vented carb spacer. These were all developed and tested for my own use and for a few friends. These products turned into business ventures for others. I have the experience from my manufacturing experience to step by step test for and isolate problems. This takes time and the right tools and equipment and you can't be in a rush or think with one ride around the block the problem is solved. To me this is fun. When I get into a project it's almost a 24 hour day, I even dream about them.

Now, food for thought regarding the 1 lb check valve you propose: I see no downside in its installation beyond just complicating a simple solution, but question the need for it in the first place. First, you reported that the sight glass showed no significant movement with the return line open or closed, so the reported engine spin of 4 or 5 revolutions shouldn't have been fuel related. Second, a negative pressure in the line theroetically could pull fuel into the pump as it is being sucked out, as both pump valves are forward directional. However, if the pump does in fact drain back, the fuel in the carb should be adequate to prime the pump again, wouldn't it? Perhaps these questions can be addressed at your next test run?
You have to read my post again, I already explained EXACTLY WHY the check valve is required. When you shut the engine down and the fuel draws a 1/2 to 1 lb vacumn on the carb line and pump draining back it needs to be corrected. Why do you think they put a check valve in the pump?? Without the valve in the pump the fuel in the carb line, pump and tank to pump line would all drain back. The pump valves have very light springs and I wouldn't be surprised if the vacumn created by the return line drain back wouldn't open the pump valve?? It takes quite a length of time to fill the line, filter bowl and pump when the fuel drains back. In doing some research all the cars I found with return lines all had check valves.
I already addressed all the questions I think are required. Maybe it's time for you do a little hands on testing or wait for the final results after which I will post my findings. G.M.
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Old 04-19-2014, 07:17 PM   #66
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Found an Airtex fuel check valve, all brass with 1/4" male pipe in and out. $10.00 at sears, $14.00 Auto Zone. Emailed Airtex to find the operating or spring pressure. Ordered 2 from AZ will be in tomorrow and will try one on Monday. Couldn't up load pictures, new camera has to much resolution so I have to reduce the size to upload to Fordbarn. Will fool with it tomorrow. G.M.
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Old 04-19-2014, 08:27 PM   #67
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Default Re: Vapor lock 1 and 2

your on the rite trail, the fuel now days you have to look for anything without corn squeezins, back in the 1980s I worked for a Plymouth dealer, and on hot summer days custmers complained about stalling out , me and another old timer new it was vapor lock since these carburators sat over the exhaust manifolds, just like a coffee pot they would perk over, then Chrysler came out with a kit to install with a electric fuel pump and line kit to return hot fuel from the carb back to the tank keeping fresh cool tank fuel in the carb at all times , fixed the problem, I haven't had any stalling problems with my 50, but long crank time on hot soaked motor until I quite using gas with the corn in it, hope this helps
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Old 04-19-2014, 10:22 PM   #68
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What I have been wondering is if I return the maximum fuel to the tank and the fuel tank gets low on a 100 degree day with the high road heat under the tank how hot the fuel in the tank might get? By maximum fuel I mean having just enough fuel to maintain 75 MPH and returning the rest. This would give maximum cooling of the pump but also heat the fuel in the tank more. I may have mentioned this but for a trip on real hot days fill the tank in the morning before leaving with cool gas out of the under ground tank and it should stay cool until the next fuel stop. This would be rare but a lot of us have made long trips on hot days and had problems. G.M.
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Old 04-19-2014, 10:56 PM   #69
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What I have been wondering is if I return the maximum fuel to the tank and the fuel tank gets low on a 100 degree day with the high road heat under the tank how hot the fuel in the tank might get? By maximum fuel I mean having just enough fuel to maintain 75 MPH and returning the rest. G.M.
At 75 mph getting 15 mpg that's only 5 gallons per hour or 1 cups per minute! The stock mechanical pump at idle pumps one pint per minute or 7 gal per hour. At highway speeds typical fuel delivery volume is .5 US gallons (two quarts or 8 cups) per minute or a pint in 15 seconds. That is 6.4 times the flow necessary at 75 mph. I don't think you need to worry about sufficient volume or flow at 75 mph.

(Pump output specs from here: https://www.fordbarn.com/forum/showthread.php?t=112181)
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Old 04-20-2014, 09:14 AM   #70
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At 75 mph getting 15 mpg that's only 5 gallons per hour or 1 cups per minute! The stock mechanical pump at idle pumps one pint per minute or 7 gal per hour. At highway speeds typical fuel delivery volume is .5 US gallons (two quarts or 8 cups) per minute or a pint in 15 seconds. That is 6.4 times the flow necessary at 75 mph. I don't think you need to worry about sufficient volume or flow at 75 mph.

(Pump output specs from here: https://www.fordbarn.com/forum/showthread.php?t=112181)
Read my post again. I am taking fuel from what is being supplied to the carb by letting some portion return to the tank. What portion I don't really know I can only look in the filler neck and see more or less fuel being returned. I put the return fitting about 5"s down in the filler neck so I could see the fuel being returned. I can also watch the carb line pressure gauge and see the pressure drop as I open the return needle valve returning more fuel. With the return needle valve wide open I can only get the pressure gauge down to about 1 1/2 lbs. This indicates the .130 ID of the return line is now the restrictor. There will be some point at which there won't be enough fuel to go 75 MPH. At this point of diminished fuel supply to the carb it may only go 60 MPH or even less depending on how much fuel is supplied to the carb fuel bowl. At this point the needle or in my case the ball valve in the carb will remain wide open with the fuel level in the bowl being controlled by the metered amount of fuel coming into the bowl. I think the engine would not run at a steady speed as the supply would vary some. The metering device is the amount of fuel being returned through the fuel return line back to the tank. From what I have seen on the carb fuel line pressure gauge I will never be able to return enough fuel through the return line to get to the fuel starvation point at 75 MPH. Why, because the approximately .130 ID of the 3/16" return tube. The .130 ID is a restriction metering the amount of fuel returned. If I installed a 1/4" return line then I could return enough fuel to starve the engine at 75 MPH. G.M.
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Old 04-20-2014, 10:22 AM   #71
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Since the mechanical pump produces over 6 times the volume necessary to sustain 75 mph you can return 5/6 of the fuel by the return line and still have enough flow into the carb. As you said, your return line that's smaller than your supply line will create sufficient pressure and flow without any further restrictions. I figured that all out when I was about to install a return line but then figured out that it won't help with my most common vapor lock problem - starting the engine after sitting hot out in the sun shut off for 10-20 minutes. Oh, it starts OK because all of the fuel hasn't boiled out of the carburetor but since the gas has all boiled out of the pump after going a few feet the engine uses up the gas in the carb, hasn't got any more from the pump, and dies and won't start again. I don't see a return line helping with that problem. It will be interesting to see if it does on yours.
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Old 04-20-2014, 01:16 PM   #72
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It will work, NO doubt about it. And with Bob Shewmans 1/2" vented spacer under the carb there will be little and I suspect NO lose of gas after shut down in the carb. But I don't have to guess about this. I have a fuel sight glass on the carb and will leave it on for a month which shows the fuel level in the carb bowl at all times. So next week I will drive the 39 and do a few other checks on the return line and when I get back cover the radiator and get the temperature up to 200, shut the engine down and won't open the hood until the next day and will see how much fuel is in the carb. Pretty simple and then I know what's going and not be misled by guess's. G.M.
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Old 04-20-2014, 05:01 PM   #73
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What you really need is a "sight glass" for the fuel pump. That's where the vapor lock hits mine. Carb has plenty of gas to start but then dies 'cause the pump only has vapor in it. Maybe it's an altitude thing. Guess I won't know unless you can test yours at 5-10,000 feet where I live and drive. Shucky darn. Guess I'll just have to keep relying on my handy dandy electric fuel pump.
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Old 04-20-2014, 07:31 PM   #74
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You don't need a sight glass on the fuel pump. All you need is a laser pointed thermometer. When the top of the fuel pump gets to 135 degrees your in trouble. My pump will no longer get near 135 with the fuel return line will post the results later this week I expect the pump to remain below 125 degrees with the return line. A pressure gauge in the carb line will also show you when a vapor lock is coming. Fuel pressure drops as the pump gets hotter and when a full vapor lock is starting the gauge drops to a little less than 1 lb and starts jumping from less than lb to about a 1 lb and a half. G.M.
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Old 04-21-2014, 06:34 AM   #75
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At 75 mph getting 15 mpg that's only 5 gallons per hour or 1 cups per minute! The stock mechanical pump at idle pumps one pint per minute or 7 gal per hour. At highway speeds typical fuel delivery volume is .5 US gallons (two quarts or 8 cups) per minute or a pint in 15 seconds. That is 6.4 times the flow necessary at 75 mph. I don't think you need to worry about sufficient volume or flow at 75 mph.

(Pump output specs from here: https://www.fordbarn.com/forum/showthread.php?t=112181)
The gas available IN the carb is reduced by the .098 hole in the carb needle valve input. You need to calculate how much fuel will flow through a .098 hole. Also this amount varies with pressure. What is it at 2 lbs, 2.5 lbs and 3 lbs. The pressure of the fuel pump remains the same from idle to higher RPMs. Once the pressure is adjusted by pump spring, stroke and push rod length it stays pretty stable. With a pressure gauge in the carb line there is no change in fuel pressure at various RPM's.
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Old 04-21-2014, 09:52 AM   #76
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The gas available IN the carb is reduced by the .098 hole in the carb needle valve input. You need to calculate how much fuel will flow through a .098 hole. Also this amount varies with pressure. What is it at 2 lbs, 2.5 lbs and 3 lbs. The pressure of the fuel pump remains the same from idle to higher RPMs. Once the pressure is adjusted by pump spring, stroke and push rod length it stays pretty stable. With a pressure gauge in the carb line there is no change in fuel pressure at various RPM's.
At 1 lb. of pressure 12 gallons per hour will pass through your .098" hole. That's still over twice the volume you need to sustain 75 mph (5 gph). At 2 lbs. it's 17 gallons per hour (3 times the amount needed) and at 3 lbs. 20.8 gallons per hour (4 times the amount required). So, no worries about volume.
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Old 04-21-2014, 03:16 PM   #77
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At 1 lb. of pressure 12 gallons per hour will pass through your .098" hole. That's still over twice the volume you need to sustain 75 mph (5 gph). At 2 lbs. it's 17 gallons per hour (3 times the amount needed) and at 3 lbs. 20.8 gallons per hour (4 times the amount required). So, no worries about volume.

I wasn't worrying about my car I knew I would have plenty of gas. I just thought you needed something to do. Thanks for figuring it out. What has always made laugh is these guys with dual carbs putting on 3/8" fuel lines when the gas is going through a .098 hole. There is more than enough gas coming from a stock pump and the 1/4" line to feed 3 carbs. G.M.
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Old 04-21-2014, 04:32 PM   #78
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What has always made laugh is these guys with dual carbs putting on 3/8" fuel lines when the gas is going through a .098 hole. There is more than enough gas coming from a stock pump and the 1/4" line to feed 3 carbs. G.M.
Yeah, that's like the guys who use 8-10 ga. wire for the speakers in their cars. Talk about overkill!
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Old 04-22-2014, 05:36 PM   #79
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Had some time this morning and put the Airtex fuel valve on the 39. I took off the return line needle valve so the only restriction in the return line is the little over 1 lb fuel check valve and the .130 ID of the line. If larger return tube is used one of the fittings will to have about a .125 orfice.to restrict the amount of fuel returned. So now all I have is a "T" in the carb line, the fuel check valve and the 3/16" OD return line which is steel brake line. I started it up and the fuel pressure at about 350 to 375 RPMs idle is 1.5 lbs.
Speed the engine up to 450 to 475 and fuel pressure go's to 2.5 lbs. This is lower fuel pressure because a good potion of the fuel is being returned to the tank. Without the return the pressure was 3.5. Let the engine warm up to about 160 and checked the temperature of the gas tank which was 77 degrees so we will assume the fuel was 77 degrees. At 160 engine temp I checked the top of the fuel pump, 95 at the top and 126 at the bottom. Checked the fuel bowl on the carb, 85 and the intake manifold below the carb, 158. This is something I forgot about, the cool fuel cooling the carb.
Wouldn't get over 175 degrees as it was only 75 outside. I put the fender cover over the radiator and left it run about 20 minutes and got it up to 210 degrees at the bottom of the top radiator tank. Top of fuel pump now read 93 and bottom of pump was 126. carb was 84 at the fuel bowl and 172 on the intake flange. I still have the fuel sight glass on the carb so I can watch the fuel level in the carb. I shut the engine down, closed the hood and tomorrow I will see where the fuel level is in the carb.
This looks better than I thought it would. NO MORE VAPOR LOCK. G.M.
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Old 04-23-2014, 09:45 AM   #80
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Went by the shop this morning and after hot shut down with the hood closed all night the fuel in sight glass of the carb fuel bowl showed right on the full line.
No lose of fuel in the carb. Even with a low battery I hit the starter and it fired right up on the first turn. This was a result of cool gas and Shewman's ventilated 1/2" carb spacer. G.M.
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Old 04-23-2014, 12:34 PM   #81
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The most typical problem with vapor lock is vaporization of the fuel in the fuel pump, not total boiling out of the fuel in the carburetor bowl. Anyone that's ever had vapor lock knows that if you wait long enough the fuel pump will cool down enough to condense the fuel back into liquid so that the pump will pump. (That can even be rushed by pouring water on the pump, pushing a half grapefruit onto the top of the pump, etc). So, overheating the engine then leaving it all night is, of course, going to allow the pump to cool and condense the fuel and have no problems starting in the morning. The true test would be taking a 30 mile drive in 90+ temperatures, stopping and parking in the sun without opening the hood for 20 minutes, then starting up and seeing what happens. I look forward to the results of that test. Let us know how it goes.
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Old 04-23-2014, 01:18 PM   #82
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The most typical problem with vapor lock is vaporization of the fuel in the fuel pump, not total boiling out of the fuel in the carburetor bowl. Anyone that's ever had vapor lock knows that if you wait long enough the fuel pump will cool down enough to condense the fuel back into liquid so that the pump will pump. (That can even be rushed by pouring water on the pump, pushing a half grapefruit onto the top of the pump, etc). So, overheating the engine then leaving it all night is, of course, going to allow the pump to cool and condense the fuel and have no problems starting in the morning. The true test would be taking a 30 mile drive in 90+ temperatures, stopping and parking in the sun without opening the hood for 20 minutes, then starting up and seeing what happens. I look forward to the results of that test. Let us know how it goes.
READ my post it's titled V1-1 and VL-2. Vl-1 was the fuel boiling in the carb after shut down. I posted this was no longer a problem with Shewman's 1/2" ventilated carb space, VL-1 over and done.
VL-2 was fuel vaporizing in the fuel pump when the fuel pump gets between 130 and 135 at the top above the diaphragm where the fuel is.
Driving the car, getting it hot and letting it sit in no difference than getting it even hotter in the garage and letting it set for a period of time and restarting. I will be driving it later this week and will report back but the results will be the same as last nights findings. Static tests on some problems are sometimes better than driving, the conditions are controlled and the same each time. G.M.
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Old 04-23-2014, 02:07 PM   #83
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who sales the shewman"s ventilated spacer. does anyone have a contact. i installed the airtex fuel pump and would like to have the spacer to.
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Old 04-23-2014, 02:09 PM   #84
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Default Re: Vapor lock 1 and 2

I installed the spacer but it didn't do me any good because the heat that affects the carburetor after shut down is coming from the hot air under the hood in the engine compartment as much as from the hot engine block.
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Old 04-23-2014, 02:13 PM   #85
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Default Re: Vapor lock 1 and 2

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Originally Posted by G.M. View Post
READ my post it's titled V1-1 and VL-2. Vl-1 was the fuel boiling in the carb after shut down. I posted this was no longer a problem with Shewman's 1/2" ventilated carb space, VL-1 over and done.
VL-2 was fuel vaporizing in the fuel pump when the fuel pump gets between 130 and 135 at the top above the diaphragm where the fuel is.
Driving the car, getting it hot and letting it sit in no difference than getting it even hotter in the garage and letting it set for a period of time and restarting. I will be driving it later this week and will report back but the results will be the same as last nights findings. Static tests on some problems are sometimes better than driving, the conditions are controlled and the same each time. G.M.
Be sure that your driving test is under the same circumstances as previous ones in which you have had vapor lock affect the fuel pump that either made it hard to start or die shortly after starting then not starting again. Any difference in circumstances between the new test drive and previous drives with vapor lock will not be a "controlled" test that proves anything.
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Old 04-23-2014, 03:53 PM   #86
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Default Re: Vapor lock 1 and 2

its commonly thought that the fuel jumps the 1/2 " up to the needle valve and siphons back to the pump .
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Old 04-23-2014, 04:10 PM   #87
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its commonly thought that the fuel jumps the 1/2 " up to the needle valve and siphons back to the pump .
Fuel can't syphon through the air it the top of the carb fuel bowl. It would have to be pressurized at the bottom to raise the fuel then the needle valve would close??? G.M.
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Old 04-23-2014, 04:15 PM   #88
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I installed the spacer but it didn't do me any good because the heat that affects the carburetor after shut down is coming from the hot air under the hood in the engine compartment as much as from the hot engine block.
I don't believe it. Everyone else who used Bob Shewman's 1/2" vented spacer got results. But of course your one of the few that his thermostats didn't work either. You had a crusade against any product Bob made on this fourum before you ever had them?? What seems to be your game?? G.M.
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Old 04-23-2014, 04:24 PM   #89
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Be sure that your driving test is under the same circumstances as previous ones in which you have had vapor lock affect the fuel pump that either made it hard to start or die shortly after starting then not starting again. Any difference in circumstances between the new test drive and previous drives with vapor lock will not be a "controlled" test that proves anything.
It can't get vapor lock in the pump until the fuel reaches 130 degrees and I can't get the fuel anywhere near that with the fuel return line. No 130, no vapor lock. What's the sense of looking for something that isn't going to happen. As far as testing I probly have another 25,000 on this 39 testing water pumps, thermostats, alternators and other products in the shop. I don't think I need to be told how tor run a test. G.M.
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Old 04-23-2014, 04:34 PM   #90
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Default Re: Vapor lock 1 and 2

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Fuel can't syphon through the air it the top of the carb fuel bowl. It would have to be pressurized at the bottom to raise the fuel then the needle valve would close??? G.M.

Right you are.
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Old 04-23-2014, 04:37 PM   #91
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who sales the shewman"s ventilated spacer. does anyone have a contact. i installed the airtex fuel pump and would like to have the spacer to.
Jerry Bob's phone number is 1-610-933-6637. He is in Pa. His email is
gadgiteer@aol.comr Your talking about an Airtex fuel pump which is just like the original Ford pump. This has nothing to do with preventing vapor lock. I put a return fuel line in the pump to carb line using an Airtex fuel check valve on the return line. This allows a portion of cold fuel from the tank to keep circulating through the fuel pump cooling it as it returns through the return line back to the tank. G.M.
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Old 04-23-2014, 07:30 PM   #92
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Default Re: Vapor lock 1 and 2

Going by some earlier posts on this thread you can see that some people beleave just that ! .That that the carb bowl can empty out by draining back .Has any one bothered to lift the carb top to see the fuel level in a vapour lock situation ?
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Right you are.
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Old 04-23-2014, 07:42 PM   #93
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Default Re: Vapor lock 1 and 2

Ted since you brought it up that would be a good project for you. Please report the results. G.M.
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Old 04-23-2014, 09:26 PM   #94
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Default Re: Vapor lock 1 and 2

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Going by some earlier posts on this thread you can see that some people beleave just that ! .That that the carb bowl can empty out by draining back .Has any one bothered to lift the carb top to see the fuel level in a vapour lock situation ?
The engine doesn't die immediately when the fuel pump vapor locks and stops pumping. It will continue to run until the gas is all gone from the carburetor and the fuel pump isn't replacing it. That's when the engine dies and won't start again until some gas is pumped into the carb either by cooling the mechanical pump to get the gas vapor to condense back into liquid so that it will pump again or by pumping gas into the carb with an auxiliary electric pump. So, when the engine dies, obviously there is no gas in the carburetor bowl. If there was, the engine wouldn't die. Don't need to take the top off of the carburetor nor have a sight glass on the carburetor to know that. It's common sense.
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Old 04-23-2014, 11:57 PM   #95
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Default Re: Vapor lock 1 and 2

If this were a democracy, I'd vote to close this thread. No, we're not having fun here.
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Old 04-24-2014, 03:17 AM   #96
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Default Re: Vapor lock 1 and 2

GM I might take you up on that .
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Ted since you brought it up that would be a good project for you. Please report the results. G.M.
Prof Henry no offence meant.!
What I cannot understand is how can a electric pump works but a mechanical one doesn't ,since they both have a diaphragm.
Keep up the good work with your road trips .
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Old 04-24-2014, 03:37 AM   #97
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Default Re: Vapor lock 1 and 2

Flathead Ted:
It's the locatation of the pump's
The Mechanical pump is on the motor, ( Picking up the heat of the motor )while the electric is near the fuel tank, (a much cooler area )
I don't know if any one has tried to heat up the electrical pump but More then likely
It would not pump.
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Old 04-24-2014, 05:00 AM   #98
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Default Re: Vapor lock 1 and 2

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If this were a democracy, I'd vote to close this thread. No, I'm not having fun here.
Stop reading it then. Simple enough.
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Old 04-24-2014, 08:44 AM   #99
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Default Re: Vapor lock 1 and 2

Quote:
Originally Posted by BILL WZOREK View Post
Flathead Ted:
It's the locatation of the pump's
The Mechanical pump is on the motor, ( Picking up the heat of the motor )while the electric is near the fuel tank, (a much cooler area )
I don't know if any one has tried to heat up the electrical pump but More then likely
It would not pump.
And, it's not only the difference in temperatures but also the electric pump is located below the level of fuel in the tank so it is gravity fed whereas the mechanical pump is above that level so that, if it can't suck the fuel above its level in the tank, it can't get any. And it's not just the temperature of the mechanical pump that makes stop pumping, it's the vaporization of the fuel in it so that the pump can't pump it. So, to merely heat up the electric pump wouldn't keep it from pumping until the fuel in it vaporized. That would require all the fuel in the tank to vaporize or be gone since the liquid fuel is being gravity fed to the electric pump.
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Old 04-24-2014, 11:14 AM   #100
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Default Re: Vapor lock 1 and 2

that is probably one of the reasons alot of manufactures started placing the pumps inside the fuel tanks. to get them away from the heat of the motor and to have the gas keep them cooled.

another thought: with the c***y motor, the pump is mounted low on the right front of the motor and that provides a place in directly in the flow of cooler air and puts the pump at the same aproxamate level as the gas tank so it does not have the inhearent problems of the ford's placement that has to pull fuel up to the top of a hot motor where the fuel pump sits captive in non flowing hot air.

i do have a GM motor in my 50 and run a stock GM fuel pump on the right front in the air flow, the fuel line has been re-routed down to frame level. the motor has a 195 thermostat and AC and so runs at the 200+ degree range i have never have any problem with vapor lock.


i believe that if a person is one is going to use a stock ford fuel pump on top of a hot motor, at some point they probably will experience vapor lock. rather than going through all this "experimentation" of fuel return lines, check valves and everything else being expereminted here in this thread, doing what Old Henry has done, installing an in line, pull thru axuxilary pump down low on the frame, in the cool air flow and at the same level as the fuel tank, with a "when needed" switch (what i did on my other 50s and 41 PU) is a simple and effective souloution to this issue.

it just seems to me that what has been said here on this thread, the cure seems to be "over engineering" at it best. there is a simple souloution avalable without going overboard..

just my thought... don
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Old 04-24-2014, 12:23 PM   #101
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Default Re: Vapor lock 1 and 2

Everyone knows that Vapor Lock doesn't exist... that is until they experience it! Ford knew VL existed, if you read their tech manuals you'll see where Ford engineers were trying to figure out how to solve the problem, well up into the '60's... As we have read here, there appear to be myriad fixes for the problem. From my own experiences with VL, in various vehicles, I have found that different remedies apply to particular vehicles. For example, when our '39 LZ gets a case of VL, I open the locking gas cap, pull the choke and nine times out of ten, she fires up... the '39 CS does not respond to that "easy fix"... The one "fix" I have found, is to install an electric fuel pump as the primary pump. That has worked on our '47 Convertible and our '51 F-1. I'm about to install an electric fuel pump in our '39 CS and hope that the results are the same as in the '47 & '51.
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Old 04-24-2014, 03:25 PM   #102
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Default Re: Vapor lock 1 and 2

Vic put in a simple return line, that's the real fix.
Just came back from a 30 mile each way ride to Arcadia for lunch 85 here in Punta Gorda and just about 90 in Arcadia.
Only had an 1/8th tank of fuel when I left so the fuel was warm and some more heat added to the fuel in the tank from the returned fuel which accounts for the cooler pump and carb temps after filling the tank.
On the trip over traveled at about 65 except for about a 2 minute spurt at 90. Ran good at 90 with no notice of any fuel starvation. Water temperature was 180, slowed down to 45 for 3 or 4 miles and the temperature dropped to about 178. Stopped for lunch water temp 178, carb temp 110, fuel pump temp 112. closed hood went in for lunch. Came out in 25 minutes water temp was 184, carb 125, fuel pump 128 and carb fuel bowl right on the sight glass line 1/2" from the top.
Stated up on the first turn, drove 1/4 mile and stopped at a store, came out in 10 minutes and it started on the first turn. Went 1 mile stopped and filled the tank with 10% ethanol and it started on the first turn. Drove 25 miles and stopped at a friends, got out and checked temps. Carb was 115, fuel pump 112. Let it running about 8 or 10 minutes and temp went to 190. In 3 miles the temp came back down to 182. Went about 8 more mile through town and arrived at where I am now. Carb temp 107 and fuel pump temp 105., water 182. It cooled down slightly out here by the water. So with those results I have no doubt this is the best cure for VL along with the 1/2" vented carb space from Bob Shewman.
I have some idea's for better installation. Drill a 3/16" in the pump to carb line a few inches from the pump aiming towards the flex hose. Clean and silver solder a 2" piece of the 3/16 OD steel brake tube in the hole. Put the Airtex CI-8000 fuel valve back at the fitting installed in the filler neck with the arrow towards the filler neck. Use a brake tube fitting for 3/16" flared brake line into the input or fuel pump side if the check valve. They make all lengths of brake tube all ready flared with fittings on them. Use them from the filler neck up the frame and up the firewall along with the 1/4" fuel line that supplies fuel to the pump. Get a 3/16" ID thin fuel hose and slip over the cut off end of the return line run with the flex hose and plug it on the tube silver soldered in the carb line. There is only a lb or so of pressure in the return hose so the small band ring clamps you sqeeze will be good. I don't need to do any more testing but would like to see a few others try it so they can verify my results. You could run a plastic tube back and with and an old gas cap drilled for the tube return the fuel that way to test it. Don't forget if you use tube with an Id larger than .130 you need a .130 restrictor in the return. G.M.
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Old 04-24-2014, 04:08 PM   #103
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Default Re: Vapor lock 1 and 2

I personally like the idea of a return line to solve the problem of VL because it does not require moving parts.
Way to go George.
Thanks for all the hard work and for sharing your results.
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Old 04-24-2014, 05:06 PM   #104
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Default Re: Vapor lock 1 and 2

That sounds good George. I may give that a try, but I know the electric pumps have prevented VL in my '47 & '51... With the OEM style FP that Marv modified, to make it a "pass through", everything will look stock on the intake manifold, no block off plates on the FP stand. I'll keep a (known to be good) mechanical FP in the trunk, just in case the electric pump has a problem...
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Old 04-24-2014, 09:35 PM   #105
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That sounds good George. I may give that a try, but I know the electric pumps have prevented VL in my '47 & '51... With the OEM style FP that Marv modified, to make it a "pass through", everything will look stock on the intake manifold, no block off plates on the FP stand. I'll keep a (known to be good) mechanical FP in the trunk, just in case the electric pump has a problem...
Vic you have to try the bypass, 39 runs better with the cool gas than it ever ran on a 90 degree day. G.M.
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Old 04-25-2014, 07:57 AM   #106
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Default Re: Vapor lock 1 and 2

Congratulations G.M. Looks like you got it figured out, at least for the low lying coastal areas. Hope it keeps working for you as the temperature there rises.
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Old 04-25-2014, 08:38 AM   #107
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Try it I believe will work in higher altitudes as well. G.M.
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Old 04-25-2014, 01:27 PM   #108
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Default Re: Vapor lock 1 and 2

Yes Sounds like you got it figured GM .Didn't really want to get into this debate .I will start a new thread later when I do the fuel level tests as you suggest. Re: Vapor lock 1 and 2
I don't believe that VP is purely a vaporisation of fuel I think its a fault with the fuel system ,Pump or flex line or sucking air ,then again I might be proven wrong here . There is a myriad of things that can go wrong on mechanical pumps .sucking air at the top ,joints, leaking diaphragms, worn arm mechanism's, push rods .If electric pumps solve VL then a mechanical one should also ,the last two cars that came in from CA I pulled the aertex pumps off and did up the mechanicals ones ,the pumps were fitted in such a way that on a low tank they wouldn't get fuel . Most tank out lets are hallway up or on the top so you don't really get gravity feed if the out let was on the very bottom then a different story will result it could depend on how full the tank is .Drain back or siphoning back has been mention here .About 10 years ago I pulled a modern pump to pieces to see what valves they had in them the Ford escort had a series of laminated rubber wafers most likely Neoprene ,I fitted these in side the pump on top of the mica pictured (P4) to see how the pumping action went ,seemed to work well .I now notice that the pump kits you get now are Neoprene (P1) as apposed to the old Mica Formica type product (P4) ,so I think drain back should be near eliminated this has a much better sealing action .This topic was discussed a while back and at the time a buddy of mine was here who was a car dealer in LA for 30 years , he regularly brought cars through HI way 40 through the hot Arizona desert .I asked him if had experienced VL he said they changed the mechanical pumps more than once and the problem went away . I don't really have time for this I am a one finger typist but more to add later .
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Old 04-25-2014, 04:49 PM   #109
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Default Re: Vapor lock 1 and 2

Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.
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Old 04-25-2014, 08:12 PM   #110
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Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.
I went back and saw your other post where you had VL and poured water over the pump to get running. With 4.5 lbs pressure your VL heat range is a little higher. Since you have a pressure gauge installed let the engine get hot watching the carb line fuel pressure. I have found the hotter the pump gets the lower the fuel pressure. When the pump temperature gets about 130 the fuel pressure drops to down about 1 lb . This is right at VL range. Next the fuel pressure will start to bounce up and down, this is VL starting, next is a full blown VL. You need a laser pointed thermometer which costs about $30.00 to see the temperature on the top of the pump. G.M.
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Old 04-25-2014, 09:28 PM   #111
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Default Re: Vapor lock 1 and 2

I have owned and driven several flathead Fords in my lifetime and have never experienced a vapor lock. I have driven the `35 on 90 days without an issue. On the other hand as a kid working in a service station I saw lots of clothes pins on fuel lines...
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Old 04-26-2014, 07:10 AM   #112
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VP exists! GM, when you have would up your experiments and have a successful go, would you please post a diagram, pics and bill of materials. I truly appreciate your efforts.
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Old 04-26-2014, 07:22 AM   #113
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Default Re: Vapor lock 1 and 2

I just returned home late eve. from a near 2700 mile trip through the southern states with Fla being the destination state in my '50 Ford. The first day, Apr. 13, it was a moderately hot day in Va as I headed south. I filled my tank at the northern end of Va on I-81 at the Flying J around 9:00am. By noon time, I was using my electric pump to aid the gas flow on any long grade. Later in the afternoon, I filled again and for the rest of the trip, even in slow traffic in Orlando, it never ever missed a beat. ????
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Old 04-26-2014, 07:42 AM   #114
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Default Re: Vapor lock 1 and 2

No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.
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Old 04-26-2014, 09:18 AM   #115
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No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.
How do you know you have 4.5 lbs of fuel pressure at Idle and higher RPMs with out a gauge?? G.M.
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Old 04-26-2014, 09:44 AM   #116
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Originally Posted by jimTN View Post
VP exists! GM, when you have would up your experiments and have a successful go, would you please post a diagram, pics and bill of materials. I truly appreciate your efforts.
Thank you Jim, The only thing I have to refine is the ID of the return or a drilled orfice in the return line. I think the fuel pressure is just a little low with the .130 ID of the return line controlling the fuel pressure. I had a little incident Friday when it was a little over 90 and driving for an hour or so I stopped with the black car sitting in the sun with the hood closed for 1/2 hour. Came out and started it and it took about 4 turns of the engine, went about 100 yards and it stopped running. I kept it rolling in gear, flicked the switch off and on with no change. Pumped on the pedal and it came back to life. I guess the whole thing lasted about 50 feet. Ran fairly good about 3 miles back to the shop where I pulled it in the garage and checked the fuel pressure which was down to 1 lb. Engine was about 190. I want to look at it Monday and see what the fuel pressure is cold and boost it up some with an orfice in the return. I'll completely block the return first to see how the pump is. I have pictures and will provide a list
of parts after I test it. I put a NEW LR wheel cylinder Thursday morning and Friday it started leaking, this is the second foreign one to leak. G.M.
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Old 04-26-2014, 12:06 PM   #117
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Default Re: Vapor lock 1 and 2

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Volume could be my problem 16 OZ. in 45 sec or less the best I get is 12 oz. I wanted to pull and clean the strainer but did not have a new gasket. Pressure 4.5 # on starter and Idle.
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No gage installed, when I get a new gasket I will remove the screen ands clean it, I suspect it has not been out for many years after cleaning screen if volume still less than 16 oz. in 45 secounds I will replace the pump with an Mechanical Fuel Pump AIRTEX 578 they are about $35.
As I explained earlier (Post # 76), at 75 mph and 15 mpg (typical) the engine only burns 10.66 oz of gas per minute. So, even if you're only getting 12 oz in 45 seconds you've still got plenty of flow for a stock engine and carburetor going 75 mph. Also, you don't need to worry too much about pressure. At just 1 psi 25 oz. per minute will flow through the valve into your carburetor bowl. That's over two times the amount necessary to sustain 75 mph and 15 mpg. No need to be replacing any pumps yet if the engine is still running fine.
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Old 04-26-2014, 12:22 PM   #118
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Default Re: Vapor lock 1 and 2

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As I explained earlier (Post # 76), at 75 mph and 15 mpg (typical) the engine only burns 10.66 oz of gas per minute. ...
Just a little optimistic there with your math, aren't you? 15 mpg at 75mph?
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Old 04-26-2014, 12:35 PM   #119
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Just a little optimistic there with your math, aren't you? 15 mpg at 75mph?
I get 15 mpg @ 65 mph without overdrive. That's why I used that number.

If it was 12 mpg that would be 13.33 oz per minute. At his 12 oz in 45 seconds that's still 16 oz per minute - plenty to go 75 mph at 12 mpg.

If his mpg was as low as 10 mpg @ 75 mph he'd be right at the 16 oz per minute he'd be burning.
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Old 04-26-2014, 01:22 PM   #120
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Default Re: Vapor lock 1 and 2

With all due respect Henry, even at 65 mph, 15 mph is optimistic. Perhaps if your engine is down tuned, your tires are at 36 lbs, your foot is light, you cruise at 45 mph and never hit the brakes, but realistically, who does that anyway? I start the engine, goose the pedal to hear the rap, wind out the gears, compression brake to rap it again, hey, this is fun! Who cares about mpg unless your gas gage is broke?
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Old 04-26-2014, 01:41 PM   #121
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Default Re: Vapor lock 1 and 2

When I first started my long road trips I was curious so kept track of mpg just to see. It seemed low at 11+ not quite 12 mpg. Posted on the barn and got responses that was way low as others were getting 15-17. I had, a few years previous, put in larger carb jets to reduce my engine temperature and ping which worked but I had the thought that it also reduced my mpg. So, I put the smaller ones back in and mpg jumped to almost 15 mpg.

I don't keep track any more but it does make some difference when I'm driving well over 1,000 miles per month.

More on gas mileage here; https://www.fordbarn.com/forum/showthread.php?t=99762
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Old 04-27-2014, 09:20 AM   #122
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Default Re: Vapor lock 1 and 2

Test gage only connected to line into carb. during test.
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Old 04-27-2014, 01:28 PM   #123
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Default Re: Vapor lock 1 and 2

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Test gage only connected to line into carb. during test.
That's where you need the gauge in the fuel line, T ed into the pump to carb fuel line.
Read it cold when the engine is started and it gets lower as the fuel pump get hotter. !25 degrees on the top of the pump and below 1.5 lbs fuel pressure and the trouble starts. G.M.
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Old 05-03-2014, 08:16 AM   #124
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Default Re: Vapor lock 1 and 2

Thanks for good info,work on hold until I return to land of the winter sun in October. Gary
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