there might be a problem with working backwards
the total volume of the combustion chamber = (volume remaining inside the bore at TDC) + (volume of squish inside the head)
the shorter the stroke and the greater the size of the head dome the more your math will be out
ie:
your calc is x = pi*(r^2)*h
the reality is x = ((pi*r^2)*h)
+ y
you could measure exactly the dome volume.
remove the head and seal up the valves where they seat with a smear of vaseline
use a burette (see picture) to measure accurately the volume of the combustion dome, do this for all cylinders and make sure they are identical.
then make sure all TDC piston positions are identical.
then set compression ratio.
and you have blueprinted your combustion chamber
