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I'm having a problem with manifold gasket seals blowing VERY quickly in my 1946 Super Clipper with 356 engine, especially the furthest back gasket. When we replaced them, we used the individual gasket set (upon recommendation) instead of the all-in-one gasket. The car ran maybe 200 miles before blowing that last gasket and creating the exhaust leak again.

When we changed the gaskets the last time, we had to remove the manifold completely because one of the studs was bent, which later broke off in removal process, and then the easy out broke, so a super small dental drill later, the easy-out and stud remains were painstakingly removed from the block and a new stud put in.

My mechanic seems to think that the manifold has malformed over the years and through the heat cycles, causing it not to seat properly, which in turn causes that one gasket to blow. It's not that I don't trust him (I absolutely do) but wanted to know if anyone else had this problem or had an idea?

I'm starting to source a replacement exhaust manifold, so if anyone has one laying around... :)

Thanks for the help!

Have a machine shop check and surface the manifolds as an assembled set to verify flatness. This is commonly needed after the manifolds have been separated or replaced.

BEFORE installing the manifold loosen the bolts that hold it to the intake manifold. This ia GENERAL practice and NOT Packard specific.

It is not alays necessary to do that. It depends upon various circumstances. The mechanic should be able to tell depending on how the stud nuts feel when tightening.

Variations in gasket thickness (OEM vs replacement etc) can effect this.

It is a hand fitting operation. Not just a "throw the bolts to it" operation.

Quite possibly the manifold is warped.

A month ago i had a integral cast intakee/exh manifold on a Z120 Continental engine that had warped almost 1/8 inch. It had ran under MY sole ownership or over 20 years and suddenly snapped an ear on th manifold. I'd never had the manifold removed in the time i owned and operated it. Probably poor fitting of the manifold by previous owner. I don't know.

Fitting the manifold is not just a "throw the bolts to it" operation.

One must kind of feel their way thru it. NOT something the average joe the mechanic type ever does.

Let me guess, it's blowing the gasket at the REAR most cylinder????
Humor me. WHICH cyclinder is it blowing on???

ok. i reread your post indicating "furthest back" which would be #8 cylinder.

Again this is NOT Packard specific but common among ANY ENGINE especialy streight 8's.

Probably due to flooding. Carb running over into manifold or other too much choke. BOTTOM LINE: too much gas getting into manifoldthru the intakee or carb.

Too much gas/ too much choke will not blow a head gasket

Fred, did you mean to say 'head gasket' or exhaust as is being discussed here?

I would guess the manifolds need to be surfaced, nothing unusual about that, a pretty common need.

Too many late nights working on my project, think I may have blown a gasket myself. Yes I did mean to say manifold gasket but too much gas will not blow any gasket in my experience.

Never seen a muffler with the side blown out of it???? It's usualy due to filling up with gasoline. Happened to me about 3 years ago.

Of course that was on a relatively modern car with ECM. The ECM was bad. It split the muffler AND blew the exhaust manifold gasket and and enuf carbon from the tail pipe to paint a door with. ODDLY ENUF it did not blow the head gasket. Of course it sounded like a 12 gaauge shot gun going off.

The flooding can blow head gasket too. Probably just depends on when the fuel ignites relative to the piston/valve positions.