I know the head has been skimmed, so I measured the combustion chamber volume with a graduated syringe. It measures 38 cc. Adding 6.63 cc for a head gasket nominally 2 mm thick and 2.7 cc for the dish in the piston gives me a combustion chamber volume of 47.33 cc, and a compression ratio of 6.26:1, quite an increase on the 6:1 stock figure.
