For me, I will adjust the valves about .006" tight for aluminum heads/iron block, or .002-.004" tight on an iron head/iron block. Warm the engine up fully and adjust to hot spec. Then recheck after it's cooled down completely. That will give you a cold spec to work on, then just make sure they are all even across the board. My motor now changes exactly .006" from cold to hot. Not sure how that happened, maybe it's just luck, but it's dead on. I set them .006 tight and they are right on the money hot. Aluminum head/iron block.