Do any of those Permatex or so-calld RTV gasket
sealants need to be used when mounting a carburetor
on its pad on the intake manifold ?

My usual mechanic says no, the pad is a kind of fiber
material and is not supposed to have any sealant coated
on it. He said the pad will flex itself in place when the
nuts are tightened.

However, I think my carb might be leaking vacuum along
its mount. The engine idles normally when cold, but
goes very rough when it heats up. It doesn't appear to
be vapour lock.

Good question Tham...

I haven't heard of using sealant on a carb mount either.

Has anyone used Permatex, or an adhesive spray for a carby mount?

I guess the pressure in an intake manifold (without a turbo) is pretty low.

well silicone and gasoline vapor aren't a good match. Some brands of silicone may work.

Something to watchout for... tiny bits of silicone could be bad for the passages in the carb.

the paper gasket is all it needs, maybe use a slightly thicker one if you have something ugly to seal.

the most vacuum it will be under is 1 atmosphere.

I guess you could use some of that Hylomar head gasket copper adhesive spray.....

I have always use permatex on N/A systems.
Its only for the 2 gaskets between the manifold, bakealite spacer and the carbie.
Silicon/silastic etc will eventually dissolve from the fuel.
The rest of your carbie shouldnt need any sealant if all surfaces are flat. If they arent flat - you should make them flat.
Hylomar doesnt stick to aluminium so its not suitable.

Tell your mechanic that if he is a mechanic, he should know the purpose of the bakelite spacer is purely to prevent manifold heat passing to the carbie.

Your mechanic is correct:Quote:These fiber gaskets need no sealant, and sealant should not be used. They can be reused time and again unless they are extremely hard and brittle.

If you don't have a gasket, you can use a fuel-rated silicone RTV sealant like the Dr. uses. Make sure the package says it is OK for gasoline.

further to answer your question.

so the engine runs bad when it warms up. does it have one of those thermal vacuum switch thingies? it it changes when it warms up, then it's a temperature sensor or something that hooks to one.