ConcoursMustang Forums

1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year => 1969 Mustang => Topic started by: ninedrvr on April 14, 2022, 06:37:51 PM

Title: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: ninedrvr on April 14, 2022, 06:37:51 PM
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?
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: rockhouse66 on April 14, 2022, 09:39:13 PM
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.
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: ninedrvr on April 15, 2022, 06:46:56 AM
When I read the warning I thought that the most likely place to leak would be between the gaskets and the manifold or spacer.
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: RoyceP on April 15, 2022, 10:35:53 AM

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.
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: Bob Gaines on April 15, 2022, 01:12:34 PM
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 .
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: jwc66k on April 15, 2022, 02:49:40 PM
Have you considered "Gun Gum"?
https://www.holtsauto.com/holts/products/gun-gum-paste/
Jim
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: preaction on April 15, 2022, 04:20:55 PM
Have you considered "Gun Gum"?
https://www.holtsauto.com/holts/products/gun-gum-paste/
Jim
Jim, is this an endorsement ?
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: jwc66k on April 15, 2022, 04:53:06 PM
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
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: Daven on April 16, 2022, 02:12:49 PM
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
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: RoyceP on April 16, 2022, 09:09:12 PM
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.
Title: Re: 428CJ Donut / Exhaust Pipe Flange Gasket
Post by: Bob Gaines on April 16, 2022, 11:04:04 PM
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.