So im about to pull the trigger on some cylinder heads, and im looking at graphite or MLS gaskets (Stock GM Graphite hasnt given me any issues sofar) Obviously MLS would be the better choice, but i see that it requires the heads/deck to be under a 50 Ra rating. Does anyone know the Ra rating of the GM blocks (On average) or should i take the short block out of the car and send it off to the machine shop? Im only looking to run 10-12 lbs of boost in the long run. CR is 9.1:1, thanks for any advice

 

And you just want to slap a head gasket and new heads on a used block?

Yank the engine out. Strip it down. Send to machine shop to deck the block so that's it square then reassemble everything.

I use a Felpro MLS head gaskets on my race engine. Spray with copper spray and install. I've had the heads off a few times. Clean up old gaskets, respray with copper spray and reassemble. As long as the MLS head gasket doesn't get damaged, you can reuse them.

 

Im not so much concerned about it not being square, im more concerned about the finish and RA rating and the sealing properties and the factory deck surface being too rough for a MLS gasket.

 

Have not seen a flat deck from GM yet, Take and draw file the deck and tell what you think ??

 

A deck that isn't flat and square plus lots of boost and your head gasket will probably fail no matter what type of gasket you use.