MLS exhaust manifold gasket...

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I just received an MLS exhaust manifold gasket (it's two pieces of steel riveted together). The steel appears to just be plain stainless without any coating on either side of the layers. Has anyone ever used a gasket like this and is this normal? MLS head gaskets usually have a black coating somewhere either on the outside or between the layers, but I assume that's because they have to deal with combustion pressures and not just exhaust being pumped out of a cylinder by a piston under no compression?

Just wondering if anyone has ever used ones like these or if there's anything wrong with these or if these types are supposed to be like this.

It's this gasket:
bcard14958.JPG
 
That's normal, you find them on some intake and plenum gaskets also. The black coating and multi layers is not so much sealing but to allow movement between the parts, the rate of expansion between dissimilar metals (aluminum head, iron block) is so great it can tear a non coated conventional gaskets resulting in a shortened service life.

They are used on some plenums to LIM for the same reason even though the materials are similar metal, the LIM is hot and the plenum is cooled by the incoming air, this condition could also result in gasket shearing although nowhere as severe as a head they do last almost forever in this application.
 
Quote:
The black coating and multi layers is not so much sealing but to allow movement between the parts, the rate of expansion between dissimilar metals (aluminum head, iron block) is so great it can tear a non coated conventional gaskets resulting in a shortened service life.
Thanks! I didn't know that. Wouldn't the rate of expansion between an aluminum block and iron manifold also be great? I'm wondering then why no coating on this exhaust manifold gasket? So it's normal for the exhaust manifold gasket to just be two pieces of springy steel with no coating?
 
The Teflon (sometimes Teflon graphite or elastomer) coating aids in sealing like spray sealer used on single steel shim stock gaskets but is not the primary seal it reduces friction aiding movement, this coating would burn off quickly on an exhaust manifold. The coating is really only required on large surface area gaskets like the head gasket that require some movement.
 
If Honda made it the part should work fine. Reciprocating airplane engines used similar dual stainless gaskets successfully for many decades.
 
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