hello to every one.

Ive just put my cylinder head back on after taking it off to replace the head gasket and got the head skimmed at the same time (138.50). i wanted to find out how much clearence ive got between my valves and pistons but when it came to cranking it over manully the enigine wouldnt move it was solid. what could be the cause of this and what other ways are there to check the clearence between the valves and pistons.