thanks chaps, i have measured the piston and it is 43 thou below block or 1.09mm, so if it should be 0.5mm proud 1.5 mm roughly shoudl be correct. although 9.5 seems high for turbo.

so if i use a zetec head at 50cc then it will be 53.978 / 500 = cop ratio 9.26. still seems high. Could i get a 1mm extra gasket or more so 500 / 56.632 = 8.8:1

what psi can run safely, going to MS with stainless inlet and t3. My target is 230-250bhp will it make and be reliable?