Cooling The New Gas

[G.M.]

Carried on from previous posts is the finial results I found to cure the boiling of gas in My 39 convertible. All old Fords will not be identical as far as the heat effects on the boiling of the gas in the fuel pumps and carb. The crankshaft mounted fan years are the worst because there is no fan air across the top of the engine. This creats a big dead air area in the area around and above the fuel pump. The firewall gets to 135 degrees where the clamp is that clamps the fuel line to the firewall, The carb temp will be close to the same on all years. A 1/2" insulated spacer under the carb that is vented and reduceing the heat riser holes to 1/4" diameter completely takes care of the carb EXCEPT that these changes can not prevent the carb from getting hot from the gas being pumped into it.
Lets asume the gas line from the tank is not in contact or near the exhaust from the tank to the bottom of the firewall so we get no heating of the gas or the metal line up to the bottom of the firewall.
The bottom of the firewall is where the problem begins. The firewall in the area of the clamp that clamps the fuel line to the firewall gets to 135 degrees. This is the start of the problem, the line becomes 135 and the gas is heated to 135. The brass fittings on both ends of the flex hose get over 130. I insulated the line from the bottom of the firewall to the pump and moved it 2"s from the firewall. The fuel pump gets it's heat from the gas comming into it, the firewall and the intake manifold very close to the bottom and the gas in the glass bowl is heated from the bale and thumb nut at the bottom of the glass. You will see bubbles in the gas start at the bottom where the thumb nut touches the glass. The aluminum intake manifold is worce the a steel one. The pump is below and almost touches the pump. The steel intake has lower runs and gives about 3/4" of clearance to the pump. Even with insulation under the pump I could not stop the gas from boiling in the glass bowl and pump on a 85 degrees outside day. I had well over a month of 85 days to test what I was doing.
What I wound up with to completly over come the problem was. Raise the fuel pump 1" with a insulated spacer I had Bob Sewman make for me. I made an adjustable push rod 1" longer, with the adjustment I can adjust the fuel pressure which needs to be on the high side. With these changes the fuel was still boiling when the pump got over 125 degrees.
Next I installed a 4 1/2" 12 volt muffin fan running it on 6 volts right now. I would say it's putting out about 175 cfm on the 6 volts and can get more cfm 's if I run it on 12 volts off my 6 to 12 volt converter. If I have a problem when it gets in the 90" out I'll go to 12 volts on the fan. I also have a funnel shaped vent reducer from the 4 1/2" square to 3" round about 4"s above the pump so the air is blowing right on the pump. The air the fan is moveing is hot from the hot air space at the rear of the engine and the bottom of the hood but the moving air cools the pump. I also mounted a small aluminum heat sink from two screws of the fuel pump top which stays the same temp as the pump. I have an adjustable temperature regulator on the heat sink and is set to turn the fan on at 122 and shuts off when the pump temp drops to 107. Today it was 87 and I drove through 12 miles of traffic and stopped for lunch for less than 1/2 hour. Pump was 120 when I stopped carb was 112, water was 190 and the fan was running.
After lunch the pump was 124 from the heat build up, fan was running which I assume shut off and came back on a few times. It started right up and ran perfect. Went about 12 miles on the highway and stopped to check, pump was 112, carb 110, fuel pressure 3 lbs and coolant 182.
10 miles back to my shop pump 116, fuel pressure 2 3/4 lbs, carb 115, the thumb nut under the glass bowl 117 and coolant 180 and fan was running. Fan shut off at 107.
When the fuel gets hot the pressure from the pump drops as bubbles form the pressure can get down to 1/2 lb and the air or vapors in the pump causes large pulsations in pressure. It can jump from below 1/2 lb to 1 1/2 with the needle of the gauge constantly moving. When it is shut down in this condition the gas in the carb is boiling and the engine will be hard to start and not run good for a short time until cool gas is supplied through the system. As summer comes along I'm sure a lot of you will will experiance the temps and problems that go along with the new gas. You need to get a laser pointed thermometer so you can pin point the problem and not be changing a bunch of parts and still never find the problem. I also have Bob's flex hose with the valve that holds the fuel in the pump and line when shut down and his 180 stats that as you can see hold my coolant temperatures right at 180. This seems to be a good operating temp. If you need help or more info let me know G.M.

[39portlander]

G.M. as usual good thread with great info. I have Bob's flexhose W/check valve and just recieved my phenolic spacer yesterday. I like the idea of the fan helping with cooling the fuel supply. Keep us posted. Scott

[G.M.]

Scott I didn't like to have to put a fan in to do the job but I don't see any other way around it. It's not really to noticeable. I mounted it to the MMO injector. I'll take a few pictures, I just thought John took some when he was down here last week. Maybe he will post them. John Skip said your parts were shipped. G.M.

[ford38v8]

George, good on ya. We appreciate the confirmation of the seriously volatile fuel we get these days, and the solutions you're working on. I know you don't want to rely on an electric pump, but with the mechanical pump being so close to the problem, I'd guess that many of us would rather bypass the mechanical pump in favor of the more reliable electric. I for one would love to read a comparison of electrics tested by GM!

[JM 35 Sedan]

George, all good information on a problem that seems to be affecting many of us all in some way but some more than others. I'm having some of those same symptoms occur on my car now which first started happening late last summer. I plan to start adding some similar heat shielding on my '35 fordor based on what I saw on your '39 during my recent visit. I will add the pictures I took of those heat shielded engine components on your '39 to this post as soon as I can get them downloaded.

[rossodino34]

Sponsored Links (Register now to hide all advertisements)

I was having a conversation with an individual who lives in the San Fernando Valley (Hot) about fuel issues. He said some people with affected cars use fuel cooling dry ice containers in line. An old drag racing trick and you can buy them from Speedway. Seems a little severe but apparently it works.
Another thing he mentioned they do is put a small percentage of light lubricant in the fuel such as ATF or Marvel Mystry oil. It tends to stabilize the temperature.
I have no idea how affective these actions are but it might be worth the experiment.

[G.M.]

It was 88 here today. Went about 30 miles to lunch. Coolant 178, pump 117 and the fan was running. The fan was running after lunch and the fuel was down slightly in the bowl fuel bowl about 1/2" and pump was 122 from the heat soak. Started right up and ran smooth on the 30 miles home. Got back and coolant was 182, pump 122 with the fan running and the fuel pressure was down to 2 lbs. but steady. I put a Lasko box fan on top of the radiator blowing back over the engine and the small cooling fan behind the air cleaner cooled the pump down to 107 in about 5 minutes, as it cooled the fuel pressure went up to 3 lbs. The fan shut off at 107. I think I need more air from the fan so tomorrow I will connect it to the 12 volts converter and expect over 200 cfm which I think should do it. Take note of the effect of the close to boiling gas on the fuel pressure. If I was useing a pump that only put 1 1/2 to 2 lbs and the pump gets hot there would be very little or no fuel pumped. G.M.

[gmc1941]

GM,could you possibly show how you take all the temps and a view of the engine compartmentit would enlighten all of us. Please please?

[Henry/Kokomo]

Rossodino34 - the heavier oils should boil at a higher temperature and, therefore, raise the boiling point of the oil/fuel mixture. Might well be effective or at least a help.

[G.M.]

I thought of diesel fuel in with the gas but I wanted to see the cause of the problem and solve it. Ididn't even want to put MMO in the tank to interfear with testing the gas. At least with the infomation have I can predict what is going on and when the problem will occur. I can even add diesel and watch the fuel pressure and see how it reacts. I'll try and get some pictures over the week end. Back around WW-2 a friends father had around a 30 Essex that ran on Kero. It had a cylinder about 4"s in diameter and 14"s long on the firewall. This had gas in it. The car was started on gas and had to warm up good before switching to kero. If it wasn't warm it would stall. G.M.

[rossodino34]

Originally Posted by Henry/Kokomo

Rossodino34 - the heavier oils should boil at a higher temperature and, therefore, raise the boiling point of the oil/fuel mixture. Might well be effective or at least a help.

Not being an engineer or a scientist (now we have that out of the way) the thought occurred to me that a trace of light lubricant could offset the effects of the ethanol/thinner in our gas in addition to being a passive temperature stabilizer.
Just a thought.

[John Kennedy]

My preferred way to deal with the hot gas issue is to run a smaller diameter return line back to the tank, with a regulator and an appropriate electric pump. May not be traditional, but can be done to look well underhood. You can even retain the original pump and plumb it inline for looks.

[G.M.]

If the original pump is left in the fuel is still going to get hot. If the return is after the old pump the fuel in the tank is going to get hot particuarly when the tank gets lower on fuel, the black top on the roads and parking areas also increase the tank temperature. Depending on the year of the car the hotter the fuel can get. A 39 pump will get over 135 when it's 85 to 88 outside. I don't know hot hot it will get at 95?? We are talking of problems that occure over 85, lower temperatures will be less effected because the engine don't get as hot and the fuel in the tank is cooler, cooling the pump as it flows through. The problem also grows at very low speeds because the engine uses less gas. I found on a 100 degree day fuel problems below 52 MPH and worse in traffic and stalling with no power in stop and go traffic. Of course when it gets to the hot fuel condition, in the 120 range when shut down the heat builds up and the fuel in the pump and carb boil. G.M.

[Fibber Mcgee]

Is there a difference between summer and winter blends or are we always on summer blends in Florida?

[G.M.]

Who knows what comes out of the pump?? Last week Ip got gas at Race Way and it boiled around 128. I got sunoco a few days ago and today I ran it in the garage for 1/2 hour with the hood down at about 20MPH engine speed with the pump cooling fan running on 12 volts. The fuel in the pump was over 130 and wasn't boiling in the glass filter bowl but the pressure was down around 2 lbs and unsteady. I think "super fan" is so powerful it is pulling hot air from the rear of the engine up and into intake and blowing even hotter air on the pump. I slit 2 2" long rubber hoses and put them on the rear edge of the hood and have a 1/4" "slot" opening for a few feet along the back of the hood. Will try this and super fan on the road tomorrow but I suspect it's to much HOT air. I have a digital meter to read the cfm so I can compare them. I bought about 8 differant fans because they didn't give the cfm rateings. I "think" you can get an idea of the cfm from the amp draw. They draw from .47 to 3.0 amps. The 3 amp one is on now. These only cost about $10.00 on eBay so I got 2 of each. I'll set each of the spares up and check the cfm tomorrow. G.M.