I was hunting for a while for some pics of machined surfaces with known RA values to compare to but couldn't come up with anything. So what are some guestimates of the RA on this block? I am thinking of running the Felpro 1094 which wants a 55 RA for use with no sealers.

 

That's about 300-something.

 

Thanks, I wonder if I can still run the shim on a surface like that even with a copper spray. I might step it up to the GM composite gasket to be safe.

 

I'm with 57k on this one, I'm a machinist and deal with this every day, that finish is at least 300 and closer to 500 I bet, usually ok for pipe flanges with gaskets and sealer but not the deck surface of a engine, the metal fire ring would never seal to that, a pure copper gasket with sealer may work. How old is that block, looks like a crack there by the coin!!!

 

Thats just some residue from cleaner. I'll go over the deck surface again if I decide to use the block as is. The block is a one piece rear seal roller block so it cant be too old.