ok cheers alex.

so then, if i wanted to build an experiment zetec turbo engine, by taking the pistons and machining them, it would be best to dish the middle and leave say a 5mm ring around the edge at std height? like proppa low comp pistons.

although the area machined will be minimal, will it have a drastic effect being 1-2mm lower?

and for this experiment before anyone says it will go pop - i dont care, it wont be in my car, and 1.8 zetecs are rather cheap to buy so no great loss.

just to see exactly how much power it will make at what ever boost on a std engine with machined pistons.