Should you use a copper spray on these when installing or should the surfaces be dry? I'm using permatex high temp thread sealer on the arp studs. Does the block or head have to have a special finish for them to seal correctly?

 

Cometic instructions state install dry. From what I've seen that a recipe for disaster unless the block has been decked. To tell the truth, I'd box them up and use something else.....

 

You need the right finish on the block and head, but coppercoat won't hurt and may prevent some coolant seepage. In the olden days, we used silver paint. I used Hylomar on my gaskets after reading up an what a lot of turbo and deisel guys used. You still need clean surfaces with teh proper finish, though.

 

Cometic is the only thing I can find thin enough(.021) for a high boost (20psi) application. I would have gone felpro, but its too thick and I'd have crap for compression.

 

No leaks here with dry installed cometics. They have a thin layer of viton or something on them. The surfaces must be specifically decked for MLS requirements.

You can probably have the heads decked a bit to allow for a slightly thicker gasket, then you know the heads are flat too.

 

I'm also running Cometic MLS gaskets, dry, with no problems.

 

The heads were just milled when they were at the porter. We already had to roll the head to get it milled down to where it needs to be.

 

Probably not much else you can do then aside from get new pistons. If you run a .021" gasket you'd need the piston at least .010" in the hole so you probably couldn't deck the block. A .020" difference in gasket thickness should only make like half a CR point of difference. How low of a CR are you lookin at?

 

I'm at about 9.3 with my current setup and the .021 MLS gasket. If I switched to a felpro .040 gasket, that'd put me around 8.9. I don't really want to do that low.