Carb wicking

D

doa44green

Member
I have 12 Model A carbs, both Zenith and Holley, that wick gas up the inner bowl sidewalls with gas at the 5/8" level inside. They will leak over the gasket surface and run down the outside of the bowl. The float valve in the cover is not to blame because it is not installed on the bowl. Does anyone else find this condition and is this a normal occurrence? Can a gas tank sealer be painted on the inside walls of the bowl?
Thank you for your input!!
Don
 
The engine sits in the frame at a 3-degree slope to match the drive-line angle, so the carburetor is level at this angle.

There has been trouble with poor fitting gaskets. Also there are vent holes in the float bowl that will leak gasoline if the gasoline level is excessive.
Now I give you colored balloons and red arrows too. :D:D:D
 

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I don't think I have ever heard of gas wicking up the side walls of the carb bowl. When you are driving around, the gas has got to be sloshing around in the bowl, especially when you get to a stop sign. With the gas level set down 5/8 in., you are placing the gas level right at the top of the Cap and Main Jets. Even if the float level valve is working perfectly, you might smell gas in the garage because of evaporation out of these jets. Also, know that for the float valve to seat tightly, the level does have to rise slightly to get enough seat load to achieve a tight shutoff. This is a characteristic of any valve that must shutoff tightly. This is why I also like the soft viton seat float valve because the valve will shut off tightly with less seat load.

If you look at the carburetor repair manuals ("Restoring The Model A and B Carburetors", Rex Reheis), the float level does not have to be precisely at 5/8 in. down.
As long as the Compensator Jet in the carb bowl is always covered with gas, the level can be lower. I like 11/16 in. but less than 3/4 in. to prevent weeping as long as the car doesn't stall at stop signs. I feel it is more conservative setting to prevent gas odors. Ed
 
Guys he has been asking this same question starting back in Jan 2019, that are what the links are.

Yes gas can creep up the side of the bowl and maybe over the top, that is why there is a gasket. I did try putting some gas in an Zenith bottom section without top and yes it did creep up the side over time. Just the nature of the beast. Might be the shape or unfinshed surface?
Have a good shut off valve, run the carb dry and forget it. Read his question, he is not asking about a built carb. He is just putting gas 5/8" deep in the fuel bowl with no top on.
 
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I'm always intrigued when I read on the barn about carbs wicking so much the fuel overflows:), another one that comes up a lot on the barn is the cap and main jets needing to be dished to prevent capillary overflow.:) this sounds like the discovery perpetual motion for some lucky (or maybe unlucky) owners :D
 
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