I just pulled the heads off my 1991 Formula. Corvette alum heads #10088113. Both head gaskets are blown at both ends. I used a Felpro gasket not sure what the P/N was. (I put the engine together back in 1993) I'm thinking I should use GM #12557236 gaskets when I put it back together. The GM gasket has a smaller fire ring diameter. The Felpro's just barely sealed, the fire ring was very close to the water passages. My choice appears to be this GM gasket which has a bore of 4.000 or Felpro's 1010 which has a bore of 4.166". My block is bored .030" over. Can I use the GM gasket on a 30 over motor?

 

Anyone have any experience with aluminum heads? I was running Prestone Low-tox a/f in it for quite a while, went through 3 edelbrock water pumps that kept leaking. Last year I went back to regular a/f. Cant' find the low-tox stuff anymore, I'm thinking maybe lots of people had problems that why I can't find it anymore.

 

Fel-pro 1010 will be fine.

 

The cylinder diameter of that GM head gasket is actualy bigger than 4.00".
Your heads probabily will need to be flat milled a bit (.005" or so) as aluminum heads tend to get "brinnelled" indented by the gasket. Check the block decks for flatness using a machinists straight edge and a .004" feeler gauge..
Replace the head bolts with new GMPP head bolts and washers. retorque after initial run. Either gasket will be fine.