I have a 1955 Y-block 272 with a stock 2-barrel Holly carb. It apparently has a fuel leak that I cannot find. When I drive it somewhere, I can smell gas when I get out. I look under the hood, and there is a black gummy residue on the passenger side of the intake manifold. I can wipe it clean and start the engine and no gas leak is present. But if I drive somewhere, it happens again. Is it possible that the float is sticking intermitantly? I have already checked the screws and nuts to make sure they are tight. Have any of you had this problem with your trucks? Thanks, Jag

 

Jag,

It's possible, yeah. Another thing to check would be the float level setting...too high & you can have problems driving, but everything seems OK at stationary idle. If you get a chance, have the missus or a bud drive behind you & check for black smoke, especially on turns & dips. If you rip the carb apart, have a look at the float itself for dents or leaks, depending on type.

Another thing to look at is loose throttle shaft/body fit. Depending on the model of carb, you can get an astounding amount of gas out of them. Work the throttle for a while & see what happens. Wiggle the shaft for side-to-side & end play.

One other solution-though unlikely- is that there is a fuel line leak that ONLY happens at speed (higher RPM, more volume and/or pressure). A slight leak, just made slow drips. I saw this just once, drove the owner nuts until he figured it out. Doesn't sound like it would be in the right place for a fuel line, but I suppose a carb top might do it, if there were a few other things happening as well with the needle & seat or float. A cracked body is one other thought, though again not as a rule.

The residue is definitely fuel, right?

Is this a sudden problem, or chronic??


Someone on HAMB has the signature "Carburetor is a French word meaning don't mess with it." Actually he used a different word than "mess", but ya get the idea.

Hopefully someone will chime in with whatever I've forgotten. Saw the Who last night, still trying to get the extra voices out of my head.

 

Hi jag i had a main jet come loose (check that ) ive had a bush come loose
to on throttle shaft that will leak , my 10 cents worth

 

Good news! After several trips the leak has been repaired. I reset the float to the minimum suggested operating level and the leak stopped. I think the bowl was overflowing. Thanks for the help everybody. Another FTE group effort success! Jag