curious- if a piston is noted as a 12cc dish does that mean the dish would hold 12cc of fluid? When they advertise that does it include the valve reliefs? Same for a combustion chamber?

 

Yes that's exactly what it means. Usually the piston dish or chamber volume is measured by sealing a plastic plate over the part. A small hole in the plate is used to fill the volume with water (or other checking fluid) using a graduated burette to get the total CCs of volume. Any valve notches or other features are included in the measurement (though dished pistons rarely need notches).

 

Thanks Joe. I am using Chev pistons and they do have the reliefs in them and as I looked at them I wondered if they too were measured.

 

Compression ratio depends on the total volume in the combustion chamber, which includes any piston dish and notches, so that's why these are included in the measurement.