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Exhaust Manifold: Gasket or No Gasket ?

Started by Jack, May 16, 2006, 11:25:01 PM

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Jack

I am involved in installing EMs on my 429 and now a friendly little discussion has developed between several folks here that needs to be resolved.

Would you use gaskets, or would you attach the EM right to the heads, sans gaskets ?

Ive heard the pros and cons on this so now it is your turn !

I will listen to all views and TRY to decide !

Thanks,

Jack

Dale

OK... so I must be a bit dumb! I would have thought that of course you install gaskets. Given that exhausts always find a way to leak out of the tiniest crack, I cant imagine how theyd seal without them.
As for tha advantages of not having them, what are they? I suppose if you were competing at Indy and needed every fraction of a horsepower it MAY help with flow. But do we care if our Caddies have 320 or 320.17 hp?

Dale.

Bruce Reynolds # 18992

From the factory, there is no gasket installed between the Exhaust Manifolds and the Heads.

But, over time, and with things becoming loose as they do, the exhaust gasses will gradually eat away at the faces if the gas is allowed to escape.  

Eventually, both the head and the Manifold surfaces will require surface grinding to create a new clean flat sealing surface.   The gas is very acidic and can corode away lots of metal and eventually render a head or manifold useless if not sealed up.

But, Gaskets are included in the rebuild kits as the common thought is for the gasket to be used to take up and imperfections it save re-machining.

But again, using the gaskets also results in a lot of broken mounting lugs and cracked manifolds as people tend to tighten the bolts up too tight to ensure a perfect seal.

The Torque specs for tightening is for metal to metal contact, not squashing a gasket in between.

Hope this helps.

Bruce,
The Tassie Devil(le),
60 CDV

Rhino 21150

The Torque specs for tightening is for metal to metal contact, not squashing a gasket in between.
This statement, of course, begs the question: With the gasket do you torque more or less than specs?

Dale

Nice one Bruce. Now I know!!

Dale.

Bruce Reynolds # 18992

Gday Rhino,

I really cant answer that question, as whenever using Gaskets where no Gaskets were originally, I just go by feel, and then after the engine has warmed up, go over them again.

I have never cracked a Manifold using this method, but have replaced a lot of manifolds that have come to me already cracked.

Bruce,
The Tassie Devil(le),
60 CDV

Bob Dziewit

When I rebuilt my 1979 425, I used the stamped steel gaskets that came with the kit.  The car had no gaskets from the factory.  After about two years, the gaskets rusted out and leaked.

Joe G 12138

If you run without Exhaust gaskets, all surfaces must be equal to factory specs ( about .006 on heads and manifolds across entire length). So you can save the $12-20 cost of gaskets by spending about $150- 225 at the machine shop to bring things back to flat.
   Or, you can tighten a warped manifold to a relatively straight head, crack the manifold, and start shopping for a replacement used 429 manifold, which will also be warped.
   Be patient.....it may take a while to find one!   Joe G. (1965 DeVille).......

  ITS YOUR CALL!!!

Rhino 21150

Now that I think about it, the last exhaust manifold gasket I replaced was so long ago it was made out of asbestos! Even my last engine swap was done with the original gasket in place.
My last hot rod had a copper/berylium alloy gasket and I torqued it the same as with no gasket.

Rhino 21150

Manifold Gasket
by Richard Bates, San Diego, CA

I recently made an interesting repair to a failed exhaust manifold gasket. We were on an extended trip (4,500 miles.) from San Diego to the deep woods of Vancouver Island, BC when the gasket blew out. The primary cause of the failure was the warping of the manifold. We didnt have a replacement gasket so we cut gaskets from regular higher temperature stock. As we knew would be the case, the misalignment of the exhaust manifold with the engine block did not allow gland rings to be fit, but in this particular circumstance we needed something to augment what was obviously an inadequate seal.

The trick we used was to make exhaust manifold gland rings from copper water pipe. We cut with a hacksaw, as carefully as we could, lengths from the pipe that would extend out of the engine block just the thickness of the gasket material. These rings were split and the joint hand filed until they could be tapped firmly into the engine block counter bore. Our reasoning was that when the manifold assembly was tightened into place the gasket would be compressed somewhat and the interference of the misaligned manifold faces with the copper glands would fix them into place and provide exhaust gas barriers for the vulnerable gasket material. There was no failure of the gasket after the rings were installed. Other antique automobile engines I am familiar with do have these exhaust manifold sealing rings and they make an almost foolproof manifold seal in conjunction with a gasket. Ford had a terrible problem with warping of the manifold and had to abandon the gland ring in production. Our experience in the North Woods with this copper ring approach suggests that the seal can be greatly enhanced. It directs the hot exhaust flame away from the gasket seal and is held firmly in place.

Subsequently we have machined the manifold assembly gasket face flat, and have installed copper glands just because it is so easy to do, and as was demonstrated to us, is effective even without the ring penetrating the manifold counter bore.

Jack

Never let it be said that you wont get a spirited discussion here when it comes Caddy engines ! !

Thank you all for participating in this little excersize to help me go for/against gaskets for my 429 exhaust manifolds.

I have to tell you that I think after reading all this I think I will use gaskets, but with great care !

Thanks to my new friend John K also for his convincing case for gaskets.

I am compelled to do what should be done by the mere fact that I dont want to have to search the world again for new manifolds !

Jack