1963 340hp carburetor to intake gasket

[Ruud Z.]

I was wondering how many gaskets, baffle plates and heat plates there should be between my 3461S AFB carburator and my aluminium intake?

[Edward J.]

Re: 1963 340hp carburator to intake gasket

Ruud, there should only be a thin gasket under the carb on your 63 340 shp car. The 300hp car had a metal plate and a plastic spacer plate and then a gasket .

[Duke W.]

Re: 1963 340hp carburator to intake gasket

Also, the 340 HP engine carb gasket is different than the 300 HP gasket - no "heat slot". Check your AIM.

Duke

[Ruud Z.]

Re: 1963 340hp carburetor to intake gasket

Thanks a lot

[David B.]

Re: 1963 340hp carburetor to intake gasket

I have a followup question (and since the original one is answered, hopefully this isn't a thread hijack).

The 340 hp manifold 3794129 and gasket 3798352 don't match (they have three holes and four holes, respectively). It's always been my understanding that the gasket was supposed to match the manifold. In this case, there is a section of gasket bridging the plenum opening without surface contact on the bottom.

I've always wondered if it would be better from a performance/engineering standpoint to modify the gasket (say,with an exacto knife) to match the manifold? Alternatively, would an open plenum gasket actually be a better choice?

I know that for the last 55 years everyone has probably just used the stock gasket, but this is the kind of thing I wake up thinking about.

[Ruud Z.]

Re: 1963 340hp carburetor to intake gasket

David, be my guest.
The only reason that I can think of why the gasket is how it is, is because maybe the gap between the 4 barrels of the carburator needs to be closed of.
I cannot think of any other explaination

[Duke W.]

Re: 1963 340hp carburetor to intake gasket

Yes, I think it's a good idea to modify the gasket to match the manifold opening. Functionally it makes no difference, but since that part of the gasket is unsupported from below, there's a chance it could break off and be ingested by the engine.

Duke

[Joe L.]

Re: 1963 340hp carburetor to intake gasket

Yes, I think it's a good idea to modify the gasket to match the manifold opening. Functionally it makes no difference, but since that part of the gasket is unsupported from below, there's a chance it could break off and be ingested by the engine.

Duke

Duke-----


The original gasket, GM #3798352, was a composition type gasket. It had a steel core and coated on both sides with some sort of insulating type material, probably asbestos-laden. This type of construction was used on many carburetor gaskets of the day. It's also commonly used on exhaust gaskets of various types and embossed-type intake manifold gaskets.

As a result of the steel core, this type gasket is actually quite rigid. I'm sure this is how GM "got away with" using it in applications where it was not completely supported. As such, there probably wouldn't be much danger of it breaking off and being sucked into the engine although it still might be better to remove the unsupported sections of it for the L-76 application.

Now we come to the modern-day. The type gasket I described above is not so common today probably as a result of the asbestos content of the original gasket. I don't know what the construction is of the modern-day replacement gaskets. But, unless they have a steel core, I'd say that tr imming away the unsupported portion of the gasket is very advisable.

[Duke W.]

Re: 1963 340hp carburetor to intake gasket

I concur, Joe.

Duke