I know I'm not the only one who has dealt with constantly failing exhaust manifold gaskets but I have the heads off for a valve job and I'm trying to fix the issue once and for all. Well, maybe for a long time would be more realistic.

I know the topic has been discussed here but I am wondering if anyone stumbled onto a great fix.

In general, the manifolds are solid with no cracks or defects. I believe they are in pretty good shape for 56 year old parts. Years ago I had the manifold mating surfaces machined flat and checking them now, they still look good.  The surfaces are solid, without any deterioration and the flatness is still good checking them with a straight edge and on a flat surface plate. I will check the cylinder head surface as well but they are less prone to problems.

I will attach them to the heads before installing so this is my chance to get everything right. Obviously I will install new gaskets and figure on using a non-hardening, high-temperature sealer. I also plan to use some Loc-Tite on the threads as the bolts don't use lock washers and they have had a habit of backing out.

The gasket sides are different with one side being more perforated looking. Is there a correct way to install them?

Any other observations or suggestions?

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Looks great!

Do torque all the  exhaust manifold bolts  again. ( if possible ? )  after the engine has been run up to operating temp and cooled down 

Is just standard procedure when engine rebuilding to recheck everything at that time 

Hope this solves the  frustrating problem you have been working hard to correct so you can get her out and enjoy the experience of owning these great cars 


Just to follow up on this, it's eight months down the road and all is well. Since I made mine, I've seen these on eBay: https://www.ebay.com/itm/1963-1964-1965-1966-390-429-Cadillac-Coppe...

This is the seller's second set so I don't know how many are left. They are well worth the money if you are considering this route.

Very glad to here the copper exhaust gaskets are working as good as was anticipated

Will help many who are dealing with exhaust leaking issues to get them solved 

A job you need to do only once and done due to difficulty 

Enjoy and Stay Safe 

Nice job fabricating your gaskets. Here is a pretty good option that I use. They are grafoil gaskets from Remflex. I use them on my car with my home built headers and they work great. I would expect that they would work equally well on stock manifolds. The best thing about them is they are thick and soft enough to make up for imperfections when torqued down. They also are fairly resistant to blowing out if some of the exhaust manifold bolts back off a bit giving you a chance to re torque them before they are damaged to the point they are toast, like the stock ones. 



Very Nice job  with the repairs 

Sounds like the Super Hot Rod Classic Antique Cadillac is performing as expected after a bit of a reboot 

Enjoy your great car  —and one of a kind creation you have the pleasure of owning 


I've had custom exhaust gaskets made for radial aircraft engines in both grafoil and copper. If there is an interest I could see about having sets made and was thinking copper as Ian has done but grafoil for the manifold to pipe gasket. If there is enough interest I could look in to it. 


Which tool did you use to cut the copper material 

I do see the holes you drilled to help cut the box part out of the Center part of the gasket 

Enjoy and thanks 


After drilling the holes, I clamped them down on a mill and ran an end mill to cut the straights and connect the holes. I have the luxury of a machine shop at my disposal but copper is soft and easy to work with so I think the job could be done with hand tools. A drill, a good pair of tin snips, a Dremel and some files should be enough to do it. I got the copper from McMaster Carr.

If you need I have some copper exhaust manifold gaskets for sale...



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