bore, stroke, if you have valve reliefs in piston, chamber volume, head gasket thickness.

NHRA shows the formula for CR as follows:

chamber volume cc's + gasket cc's + deck clearance cc's + (displacement x 2.0483) ----------------------------------------------------------------------------------------
chamber volume cc's + gasket cc's + deck clearance cc's

(any of the numbers can be neagtive, such as deck clearance)

deck clearance = bore x bore x 12.87 x depth of deck clearance

volume of head gasket = bore x bore x 12.87 x thickness of head gasket

Larry