273 Commando Piston Dome Volume

Roger.... I would not argue that the mfr's don't supply the numbers, but measurements show that production closed chamber 273 heads are larger than 57 cc, so the NHRA numbers are not actual production numbers but an idealized factory minimum, to which all heads can be milled as needed to reach that number and equalize that aspect of the engines in competition.

So I kinda think the piston numbers may be the same. I also wonder if the 16 cc dome volume reflects the dome only, and the 11.5 volume includes the eyebrow volume; a 4.5 cc eyebrow volume would be make sense for what the op shows in pix.