67 EXHAUST MANIFOLD GASGETS

[Rob A.]

I understand that exhaust were originally installed without gasgets (as indicated in the judging manual). It's hard to believe they will not leak without them.....am I wrong? Can I use a high temp rtv silicone gasket maker, like permatex Ultra Copper?

[Joe L.]

Re: 67 EXHAUST MANIFOLD GASGETS

Rob-----

NO Chevrolet V-8 engines through 1979 ever originally used exhaust manifold gaskets. In 1980, with the introduction on the California-only 305 cid engines, tubular exhaust manifolds were used which DID use gaskets. However, I can assure you that NO gaskets were used on any 1967 engines. The manifolds will not leak as long as the head and manifold mating surfaces are straight and true. Usually, the cylinder head surfaces are no problem as long as they are SCRUPULOUSLY clean. Exhaust manifolds are subject to warpage. Check them with a precision straight edge or have your machine shop check them. If necessary they can be surfaced to true them up.

If you were going to use a silicone sealer on the manifold-cylinder head interface, then you might as well use gaskets---each would be about equally visible to judges. However, you can forget the high temperature silicone RTV. It won't withstand exhaust manifold temperatures at the cylinder head.

[Patrick H.]

Re: 67 EXHAUST MANIFOLD GASKETS

Rob,

I tried exhaust manifold gaskets after I rebuilt my 71's motor in 1996. They seemed to break apart and I had to replace them yearly because they leaked.

When I replaced one of my heads two years ago I had the manifolds trued. No more gaskets, no more leaks. It's actually much better than it used to be with the gaskets. I'd go without them if you can.

Patrick

[Warren F.]

Re: 67 EXHAUST MANIFOLD GASKETS

Rob: On my 'vette I have aluminum cylinder heads mating to cast iron exhaust manifolds with no gasket, and they seal just fine even though both metals have disimilar expanding rates, much worse than iron to iron mating!

[Brian McHale]

Re: 67 EXHAUST MANIFOLD GASGETS

A light coat of Permatex Ultra Copper works well and any evidence of it can be removed after fire up. Good insurance for a leak free existence.

[Jim T.]

Re: 67 EXHAUST MANIFOLD GASGETS

The original exhaust manifolds never leaked on my original owner 70, but when I put a ZZ crate engine in my 70 with aluminum heads I did have some leakage. I used the exhaust manifold gaskets the Chev used on the C4 with aluminum heads. It was a lot of extra work with such a easy engine swap because of the the air conditioner compressor removal and installation. This was several years ago and the gaskets have held up well.