Jeff Crane says Aluminum block and heads subtract .012" Iron block Al. heads subtract .006" Iron block and heads add .002"
But that's just a safe beginning. Like most others here I set mine tighter than that. Instead of the .006 they suggest I set mine at .012" cold to get the .020" I need on my al. heads.
You have to test each motor, not all of them will be the same.
Set them cold and then warm up the motor so you get around 160 F oil temps and pull one valve cover and check one set of valves to see what your motor needs
Write it down also
