Originally Posted by
coswurv
I used vauxhall c20xe pistons in one of our cars, they require the block boring to 86mm iirc, plus a little honing of the zetec little end to allow the gudeon pin to fit nicely, they sit 3mm lower in the block on tdc than the standard pistons. The engine i did also has had a kent cam, super chip, still on mfi managment using a bigger turbo with .48 exhaust housing running just over a bar of boost iirc and that made 197bhp with 239ftlb of torque so is plenty good enough really, hope that info helps.
sorry pal, but you really are down on power with a BAR of boost, i'd say the mfi needed sorting out really badly.
you ideally wan tto aim for 8.5:1 for getting good economy and response, but head down to 8:1 for getting more boost.
if you're going for big big power, then go as low as 7.5:1, i wouldn't do this unless your power is over 400bhp though as it'll be less efficient on lower boost.