With the known combustion chamber volume, CCVĬompression Ratio equals Swept volume+CCV divided by CCV
Put piston at TDC, use a measuring jug ideally a burette ( lab calibrated glass tube), whatever, fill the combustion chamber with oil to the bottom of the spark plug hole, record the oil quantity, to the nearest cc.
Forget the math, test clearances with clay as Hillbilly says, if you have a choice of head gaskets thick or thin, test fit the thin one, fit the head with one set of valves, dont need to be fully assembled inner springs will do.
