foggyjames wrote:This information might come too late, but don't write off the B20 rings - the B20 was 1986cc, just like the B200, and *might* use the same pistons and rings. It's worth checking, anyway.

B230s were larger bore, so that's no good.

You can calculate how much to skim the head by to achieve a particular compression ratio, if you're feeling clever. Measure the volume of the combustion chamber in the head (and piston crown, if it features a recess) - fill with water, then extract with a syringe, measuring in CC as you go. Divide the cylinder capacity (1986cc / 4 = 496.5cc) by the chamber capacity (it was around 65cc on a 531 we measured recently for a turbo engine), and you have your static compression ratio. In that case, it was a B230 (580cc per cylinder), so the compression ratio was approximately 9:1...about right for our 'street' turbo application. Of course it gets more interesting if you have a piston with a raised centre (high compression B200), but you can probably work something out I see yours are slightly dished, which I think makes it a lower compression (later) B200. Raising it back up to 10:1 (or even a bit higher) would work well, as long as you're willing to feed it suitable fuel!

You could play with filling the head a little short of the top, to see how many CCs that saves you...and how much you need to shave off to raise the compression to your target.

cheers

You also need to factor in any land over the piston to the top of the block and the volume of the head gasget.

James