Raising the Compression Ratio.
How to do so safely and effectively, by measurement and calculation.
CR = (Stroke volume + Compressed volume)/Compressed volume
Calculating the skim to achieve a raised CR.
NEW Compressed volume = Stroke Volume
New CR - 1
NEW Compressed Volume - Gasket Volume - In Block Volume
Height = Volume to be removed
Use this in the above equation, replacing the πR2 with 'Area', and calculate
One thou' = one thousandth of an inch = 0.001"
10 thou' = 0.254 mm, or one quarter of a millimetre
The problem is, what is the volume of the dome? Triumph six cylinder domes are 8.66mls, but I regret that I have never seen a Spitfire dome, so I cannot say what its volume would be. The Appendix explains how the dome volume can be calculated from direct measurements of a domed piston. Note the effect on CR that the dome can make!