Hemi guys - exhaust manifold gasket to use

[AR67GTX]

I know they didn’t come with them originally but this motor had some petrified ones on it and as difficult as these manifolds are to remove/install, I’m not going to experiment to see how flat everything is. I installed SCE copper gaskets and the right side sealed OK with the bead against the head. But because exhaust gaskets are both the same and fit only one way on a Hemi, on the left side the bead seated on the manifold and it leaked like a sieve.

So pulled the manifold out again (lots of fun) and studied things. I bolted the gasket to the head and found that between the slop in the manifold holes and the slop in the punched gasket holes, the gasket could slide up or down 5/32” up front and a hair over 1/4” at the back end. That apparently lets the raised bead slide into the port area in the corners if not fitted just precisely. You can see that in the photos below - look at the gasket position at the bottom in these two pictures.

I only go through all this in case someone is thinking about using these gaskets on their Hemi. I’ve used them on other engines with a lot of success but they don’t seem to be a good choice here.

Anyone got a recommendation on a good conventional exhaust gasket for the Hemi?

 

[INTMD8]

In my experience, no gasket is best for manifolds. Very very thin smear of high temp rtv on lacquer thinner cleaned surfaces.

I do the same for flat flanged headers.

 

[R413]

I used Fel-Pro MS 90049 gaskets and they have been fine for 2 years.

Installed them dry, nothing on them. New hardware, everything clean, cleaned the threads in the bolt holes. Check the bolts after a couple heat cycles. Been just fine with zero leaks. I would do it this way again.

 

[moes]

a buddy used these when he had a problem with his 70 hemi Super Bee exhaust leaking. They work perfectly, he has had them on his car for 6 years now and still no leaks. Just don't over torque the bolts


https://catalog.remflex.com/MOPAR_HEMI_Header_Exhaust_Manifold_Gasket_p/6036.htm

 

[AR67GTX]

a buddy used these when he had a problem with his 70 hemi Super Bee exhaust leaking. They work perfectly, he has had them on his car for 6 years now and still no leaks. Just don't over torque the bolts


https://catalog.remflex.com/MOPAR_HEMI_Header_Exhaust_Manifold_Gasket_p/6036.htm

I think those are the gaskets that are real brittle. If so, my friend with a 69 Hemi RR ordered some but when they arrived from shipping they were all broken up.

 

[jamey]

Try red Rtv on both sides of the gasket.

 

[6PKRTSE]

May want to place them on a surface plate to make sure they are flat and true. If so, then good. I have run Cometic gaskets on my Hemi and big blocks.

 

[AR67GTX]

Manifold surfaces looked good with a straight edge. You can tell by moving the gasket around within the limits of the hole slop at the bolt holes, that the rolled seal bead in some areas, especially the corners, falls inside the port opening in some gasket positions. If the rolled bead had been positioned about 1/16” to 3/32” further out in all directions, the problem would be solved.

 

[snakeoil24]

Have the manifolds milled and and no gaskets.

 

[Robertop]

I know they didn’t come with them originally but this motor had some petrified ones on it and as difficult as these manifolds are to remove/install, I’m not going to experiment to see how flat everything is. I installed SCE copper gaskets and the right side sealed OK with the bead against the head. But because exhaust gaskets are both the same and fit only one way on a Hemi, on the left side the bead seated on the manifold and it leaked like a sieve.

View attachment 1235571

So pulled the manifold out again (lots of fun) and studied things. I bolted the gasket to the head and found that between the slop in the manifold holes and the slop in the punched gasket holes, the gasket could slide up or down 5/32” up front and a hair over 1/4” at the back end. That apparently lets the raised bead slide into the port area in the corners if not fitted just precisely. You can see that in the photos below - look at the gasket position at the bottom in these two pictures.

View attachment 1235572 View attachment 1235573

I only go through all this in case someone is thinking about using these gaskets on their Hemi. I’ve used them on other engines with a lot of success but they don’t seem to be a good choice here.

Anyone got a recommendation on a good conventional exhaust gasket for the Hemi?

Have you heard of Remflex gaskets? I used them in my Hemi. They are very thick, and compress to "regular" thickness when you tighten the bolts, and this should take care of minor leaks.

 

[Hemirunner]

May want to place them on a surface plate to make sure they are flat and true. If so, then good. I have run Cometic gaskets on my Hemi and big blocks.

I currently run these on my turbo combo. I ran the TTI gaskets that came with my headers on my old combo. Those worked well also.

 

[AR67GTX]

I went through a lot of gasket specs and went with these advertised for stock street Hemi manifolds.

https://www.summitracing.com/parts/SCE-466080

They matched my stock manifold port sizes better than most. A lot of gaskets are for headers or Stage V heads or heads with enlarged ports.

Besides the slop in positioning the problem with the copper SCE gaskets was that gasket port corners was a larger radius than the manifold corner radius. The raised sealing bead fell off the manifold surface there and left an open path. I find nothing to indicate the manifold is warped or any other sealing irregularity - just a bad gasket fit.

 

[Hemirunner]

I went through a lot of gasket specs and went with these advertised for stock street Hemi manifolds.

https://www.summitracing.com/parts/SCE-466080

They matched my stock manifold port sizes better than most. A lot of gaskets are for headers or Stage V heads or heads with enlarged ports.

Besides the slop in positioning the problem with the copper SCE gaskets was that gasket port corners was a larger radius than the manifold corner radius. The raised sealing bead fell off the manifold surface there and left an open path. I find nothing to indicate the manifold is warped or any other sealing irregularity - just a bad gasket fit.

We started using ultra gray rtv on the dyno engines and then on the race car headers. It works really well for cast iron manifolds and there’s less chance of cracking a manifold than when using a gasket.

 

[snakeoil24]

Guys don’t use gaskets on hemis with cast iron manifolds if your recommending this you must not know anything about street hemis.

 

[69 hemibee]

a buddy used these when he had a problem with his 70 hemi Super Bee exhaust leaking. They work perfectly, he has had them on his car for 6 years now and still no leaks. Just don't over torque the bolts


https://catalog.remflex.com/MOPAR_HEMI_Header_Exhaust_Manifold_Gasket_p/6036.htm

+1 on Remflex, you'll never have a leak using these. They are brittle as they are made to compress to the contours of the mating flanges, which is why they work so well.

 

[AR67GTX]

I think I commented above that I was leery of the Remflex because a friend ordered a set for his 69 Hemi RR and when they arrived they were all broken up. For the money involved he didn’t try to go back on the shipper or seller. I didn’t want to take a chance. If I could find them locally I would have tried them.

 

[69hemibeep]

Metal to metal mill the manifolds if needed

 

[R413]

Guys don’t use gaskets on hemis with cast iron manifolds if your recommending this you must not know anything about street hemis.

Maybe not according to you, but what I do know is:
*how to assemble things that don’t leak
*that you don’t use thick header gaskets on cast iron
*what a pain it is to R&R a street hemi Ex manifold
*the more you mill something the more it wants to warp and crack. And if the last guy(s) followed these threads on here the manifold would be paper thin 55 years later when it gets milled every time it is installed.

 

[snakeoil24]

Maybe not according to you, but what I do know is:
*how to assemble things that don’t leak
*that you don’t use thick header gaskets on cast iron
*what a pain it is to R&R a street hemi Ex manifold
*the more you mill something the more it wants to warp and crack. And if the last guy(s) followed these threads on here the manifold would be paper thin 55 years later when it gets milled every time it is installed.

Most guys are buying aftermarket exhaust manifolds and Iron to iron is the best seal no matter what you say. These are not headers which always leak no matter what brand you choose.