Topic: 428CJ Donut / Exhaust Pipe Flange Gasket

[ninedrvr]

I bought 2 of these "concours" steel donut gaskets produced by Mansfield Mustang. While shopping for these I came across this from West Coast Classic Cougars; "Note! These are very difficult to seat compared to the pliable ones we sell. If you do decide to use the steel version it is recommended you apply a liberal coating of Permatex High Temperature Ultra Copper Gasket Maker " Anybody have any special procedures or techniques you can share?

[rockhouse66]

I have used a thin film of red high temp RTV on these.  If the cast manifold is pitted, then this is probably a good idea.   I don't know how much it helps, but these do not usually leak in my experience.  The exhaust pipe is softer than the donut and if you squeeze it down, it conforms to make a good seal.

[ninedrvr]

When I read the warning I thought that the most likely place to leak would be between the gaskets and the manifold or spacer.

[RoyceP]

That's been my experience. Originally the manifolds were smooth like the steel biscuits. Now 50+ years later the manifolds typically have pock marks of rust. I find a light smear of "Super Black" RTV fixes the issue nicely. Obviously the orange stuff will too but it's orange so not as easy to disguise.

When I read the warning I thought that the most likely place to leak would be between the gaskets and the manifold or spacer.

[Bob Gaines]

That's been my experience. Originally the manifolds were smooth like the steel biscuits. Now 50+ years later the manifolds typically have pock marks of rust. I find a light smear of "Super Black" RTV fixes the issue nicely. Obviously the orange stuff will too but it's orange so not as easy to disguise.

[/color] Less of a problem regardless of color if you wipe off what ever squeezes out after you tighten them down  before the silicone sets up .

[jwc66k]

Have you considered "Gun Gum"?
https://www.holtsauto.com/holts/products/gun-gum-paste/
Jim

[preaction]

Have you considered "Gun Gum"?
https://www.holtsauto.com/holts/products/gun-gum-paste/
Jim

Jim, is this an endorsement ?

[jwc66k]

Jim, is this an endorsement ?

I've used it in the past, on Fords, VWs and Honda FL350 Odysseys.
I "endorse" Crest Toothpaste and JD no 7 Sour Mash.
Jim

[Daven]

If you have to squeeze RTV on the exhaust I recommend using the copper based RTV, it has the highest temperature rating.  I think permatex may make that type of RTV.

Dave

[RoyceP]

I think temperature rating of RTV is somewhat - or maybe totally - misleading. I am guilty of using basin tub and tile white RTV in place of a header gasket because I had to be at work the next day. It worked for many years - longer than the engine lasted in fact. It was late and the only thing my parents had that seemed like it would work. It did, and very well.

[Bob Gaines]

I think temperature rating of RTV is somewhat - or maybe totally - misleading. I am guilty of using basin tub and tile white RTV in place of a header gasket because I had to be at work the next day. It worked for many years - longer than the engine lasted in fact. It was late and the only thing my parents had that seemed like it would work. It did, and very well.

+1 . Been there done that.