My old carburetors leak

Question:

I have a problem with carburetors leaking gas. I have three old Ford trucks that have old Holley 1 bbl. carburetors on them with glass bowls. They leak where the glass meets the body of the carb. I have rebuilt the carbs but they still leak even with the new gasket.

Answer:

It is likely that the surface of the casting that the glass bowl is supposed to seal against is corroded, warped or both. If this is the case, an obvious solution is to replace the bad castings with good ones.

As an alternative, you may be able to smooth out any pits or other imperfections and true up the mating surface of

the casting by improvising a bit. If you can mount the castings on an accurate drill press or (preferably) a precise milling machine or lathe you may be able to devise a way to machine the mounting surface. Something as simple as a good quality hole saw that’s sized correctly for the glass bowl could do the job. It’s also conceivable that you can use a glass bowl as your machine tool. First, make sure the edge of the bowl is straight and true. Apply an abrasive compound (such as valve lapping compound) to the surface of the casting that the glass bowl is supposed to seal against and then spin the bowl on the mating surface while applying some pressure.

Editor’s note: We spoke to this topic in the May issue but since it deals with gasoline leaking in the engine compartment, we decided to provide additional how-to information this month.