Automotive cylinder head finish

[Tony Wells]

Actually, that's a rather complex question. Or rather the answer is. The surface finish on heads varies considerably according to the manufacturers choice in gaskets, which have come a long way in the last few years. Dissimilar materials used in the block and heads requires special consideration because of the expansion rates of the materials. The gasket needs to be able to "slip" on one side, and "grab" on the other side in some cases. Some of the current gaskets are several layers thick, of different materials to make it work. It takes a bit of serious engineering to seal a modern engine. The old ways are changed. Old engines typically specified a 32 -63 range, with some as much as 125 rms, but now, you should consult a manual. Some recommend a 8-10 finish, some still 125.



Edit: "deal a modern engine" s/b "seal a modern engine"