Hello,

I am replacing the engine on my 1991 Mirage. I have a 1990 4G15 short block ready to go. The 1990 version had an 8 valve Cylinder head. I would like to use the 1991 Cylinder head I already have which is in excellent condition, however it is a 12 valve.

Has anyone mixed these two? I have checked and all of the water jacket and oil ports match between the engine and head, the 12 valve head gasket fits and matches. the only difference I see is on the 1991 block, the piston tops are relatively flat and have two curved valve recesses, and on the 1990 block, the pistons have an overall concave finish on their tops. Provided that the timing is correct, should this really matter?

Any advice appreciated.

Kevin