Carb Question

[Robert/Texas]

After about a 6 month sleep with a tank full of corn gas with the recommended amount of Stabil, I tried to start the engine. It wouldn't start until I opened the gav to over a half turn. Then the engine roared to high speed and the only way I could slow it down was to close the gav. It acted like an accelerator and I was able to drive it that way for a short distance. When closing the valve to under 1/4 turn the engine would die. After the engine warmed up it would behave normally. It has continued to act the same way for some time now. The colder the weather the longer it takes for the engine to warm up and for things go to normal.
The car is an early RPU with a repro Zenith carb which I bought for it when they were selling for $95. I actually bought 2 of these, the other for my '28 roadster which isn't experiencing this problem. The only problems I've had with these is replacing the floats soon after the corn gas got here and damaged the solder in them and several times blowing them out when debris got in them.
I'd appreciate any suggestions on what to look for.
Thanks, Robert

[Gary WA]

If the gas was left in carb during sleep mode, I always idle mine till it shuts down by it self emptying the fuel from carb. plugged jets would be my choice. once you have it running hold hand over carb opening and will sometimes suck the junk from the jets. or open up and clean. I'm sure many will check in!

[Dick Steinkamp]

Originally Posted by Robert/Texas

It wouldn't start until I opened the gav to over a half turn.

I believe this is normal for most stock As. I open mine one full turn then close it gradually as the car warms up to about 3/8 turn open. Each car is a little different, but I don't know of any other that will start when cold at less than 1/2 turn.

After the engine warmed up it would behave normally.

Again, normal...at least for me.

The only problems I've had with these is replacing the floats soon after the corn gas got here and damaged the solder in them

Solder can not be damaged by ethanol. If that was the case, all our floats would be falling apart.

[Gary WA]

Originally Posted by Robert/Texas

After about a 6 month sleep with a tank full of corn gas with the recommended amount of Stabil, I tried to start the engine. It wouldn't start until I opened the gav to over a half turn. Then the engine roared to high speed and the only way I could slow it down was to close the gav. It acted like an accelerator and I was able to drive it that way for a short distance. When closing the valve to under 1/4 turn the engine would die. After the engine warmed up it would behave normally. It has continued to act the same way for some time now. The colder the weather the longer it takes for the engine to warm up and for things go to normal.
The car is an early RPU with a repro Zenith carb which I bought for it when they were selling for $95. I actually bought 2 of these, the other for my '28 roadster which isn't experiencing this problem. The only problems I've had with these is replacing the floats soon after the corn gas got here and damaged the solder in them and several times blowing them out when debris got in them.
I'd appreciate any suggestions on what to look for.
Thanks, Robert

http://modelabasics.com/home.htm

[jm29henry]

Mine works the same

[Tom Wesenberg]

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Corn crap gas no doubt left some garbage in the carb as it evaporated.
I'd take the carb apart and clean it up.
At the very least spray some Kroil on the throttle shaft to be sure it comes back to idle.

[Robert/Texas]

Thanks to all. I decided to try to fix it today. It was 84 degrees here and the engine started normally just like it used to. I believe that Tom had the answer but can't prove it until the weather gets colder again. I'm going to clean things up though.
Regarding the floats, I have had my 2 A's and 2 T's for 18-19 years. Some time after the ethanol got here the float on one of my T's started leaking. Within a few months the same thing happened with all 3 of the other cars. None of the replacement floats have leaked. I had assumed that the float seams were soldered but they must have been sealed with something that was not alcohol proof. I kept 2 of the old floats and they are still filled with fuel.
Thanks again, Robert

[Ron in Quincy]

Robert,

When rebuilding Zenith and Holley Carbs I always test the floats to be sure they do not leak: boil a sauce pan of water, when boiling set the pan off the burner so the bubbles stop, using a long nose plier, pick up the float and hold it in the water, the hot water heats the air in the float and if there is a leak it will bubble and you can see exactly where the leak is. Using solder with a low melting point and your soldering iron seal the hole.

Regarding the jets, I put a small amount of sealant on the gaskets of the Cap and Main jets to be sure they do not leak at the base of the jets which is below the fuel lever in the bowl; I also put sealant on the threads of the GAV housing so it will not leak, this point is also lower than thane the fuel in the bowl.

I jet my Carbs so when the engine is warm you close off the GAV, this gives you better gas mileage. The only time I open the GAV 1/4 turn is when I am climbing a hill to provide more fuel to the Cap jet as the engine is working harder and usually needs the extra fuel.

Regarding the Jets, I use the following sizes openings on single Venturi Carbs.

Idle: .021
Comp: .037
Main: .037
Cap: .039 (preferred) or .038

Always check the orphus of the Main and Cap jets for no damage.

This has always worked for me, others may not agree.

Ron

[jwilliams81]

Originally Posted by Ron in Quincy

Robert,

When rebuilding Zenith and Holley Carbs I always test the floats to be sure they do not leak: boil a sauce pan of water, when boiling set the pan off the burner so the bubbles stop, using a long nose plier, pick up the float and hold it in the water, the hot water heats the air in the float and if there is a leak it will bubble and you can see exactly where the leak is. Using solder with a low melting point and your soldering iron seal the hole.

Regarding the jets, I put a small amount of sealant on the gaskets of the Cap and Main jets to be sure they do not leak at the base of the jets which is below the fuel lever in the bowl; I also put sealant on the threads of the GAV housing so it will not leak, this point is also lower than thane the fuel in the bowl.

I jet my Carbs so when the engine is warm you close off the GAV, this gives you better gas mileage. The only time I open the GAV 1/4 turn is when I am climbing a hill to provide more fuel to the Cap jet as the engine is working harder and usually needs the extra fuel.

Regarding the Jets, I use the following sizes openings on single Venturi Carbs.

Idle: .021
Comp: .037
Main: .037
Cap: .039 (preferred) or .038

Always check the orphus of the Main and Cap jets for no damage.

This has always worked for me, others may not agree.

Ron

As a new model a owner I find that really helpful. I know you solder the end of the jets and drill them out to those sizes you just listed, but where do you get the drill bits to do that? Can you pick them up that small at the big box hardware stores?

[Sparky]

I got my drill set from eBay. Look for a #61-80 micro drill set. Big box stores don't carry them. You will need a hand bit holder; don't try to use a power drill.

[Richard Lorenz]

If you add solder to the tip for re-drilling, keep the solder close to the tip. If the solder is allowed to flow back into the tip very far, you will get less that the expected flow because of the added restriction.

[Carb Guy]

As Richard L. said if the solder flows deeper into the jet which it usally does, it is very necessary to flow test the jets to see how they flow.

[Ron in Quincy]

jwilliams81,

I use original jets, I do not solder and re-drill jets. I also do not flow test jets. I pre set the idle screw at 1-1/2 turns open. When engine is cold , I slightly advance throttle, open the GAV 1/4 turn, choke and immediately release to start. After installing on my A, and warming up the engine, I fine tune the air mixture to the idle jet. I test drive the carb, check for excellaration , make emergency stop to be sure the engine does not die. When idling I open GAV 5 or 6 turns to make sure it does not effect the idle circuit.
I will mention that the Ford Owners Manual tells the customer to close the GAV after the engine is warm. Running with the GAV open will effect gas millage, 2 or 3 miles less to the gallon.

Ron

[Chris H]

Over the years I have had problems with the ethanol laced fuel they are requiring us to use in the Midwest, especially with small engine carbs. The passages are so small, they clog easily with the crap the fuel leaves behind! I usually apply a "good slug" of Sea Foam to the carb bowl, and let it soak for a while. It usually works! Not as good as disassembly and a good cleaning, but it works surprisingly well. Just my $.02 worth.