Hello, I have some questions related to mls head gaskets. I'm using Cometic gasket part number C5461-040. Is there a up and down side to this gasket? It is not mar. How smooth does the engine block in cylinder head have to be to use this gasket? I have previously used felpro 1009 with no problems in the past. I wanted to try something new and potentially a better gasket. Does this gasket need to be sprayed with the copper gasket sealer spray like a copper gasket does?

The heads and block need to be really smooth(50RA maybe) to seal up properly, don't ask me how I know Contact Cometic to get the straight scoop I have reused them dry as well as using Copper coat or spray Hylomar on them because the customers ask me to I wouldn't use any thing on them for my own use They are nitrile (rubber) coated to start with

I am on my 4th use of my Cometic head gaskets (BB Mopar), and I love them at 13.5 CR.

The correct finish on the heads and block is important. So consider resurfacing aluminum heads that have been run with other gaskets (fire ring dents).

Especially for big blocks, I don't think any sealer is needed when new. But I have always sprayed mine with Permatex Copper coat for head gaskets.