If you want to check your piston to head clearance go to your local automotive machine shop and ask them for some Plastigage. It come3s in a flattened paper tube about 9" long. Inside is a round piece of soft plastic.
You snip off an inch or two and peel the paper back. (don't throw the piece of paper away. It has marks on it that will tell you the clearance.) Then you take out the piece of soft plastic and place it on the head where you want to measure the clearance. You then assemble the engine and slowly rotate the engine over by hand for one up and down of the piston.
Then you take the head off. You will see that the piece of soft plastic has been flattened out. You compare the width of the flattened plastic against the markings on the little pieces of paper that you saved. When you find the marking that matches the plastic the paper will tell you what clearance that equates to. Simple huh!