You can measure the piston dome volume indirectly for (pistons that have a ridge around the edge) by putting them in a cylinder so the top of the dome is even with the top of the cylinder. Then use a burette to measure the volume around the dome i.e. the volume that isn't the dome. Subtract the volume that isn't the dome from the calculated volume for this piston if it had no dome and you get the volume of the piston dome. I installed the top ring and used some Vaseline to seal the ring gap.
-Chris
