[Trackrash]

Motors built after '71 had lower compression ratios. Thus the 2,2 piston upgrade.

If you want to go with a 2,7 (90mm RS P&C) that motor only had 8.5-1 CR.

I guess you will want to get 90mm cylinders and use something like a JE piston to get the CR.

If you use 90mm cylinders you will have to bore out the case spigots and heads for the larger bore.

If it was me, I would either go with a high reving, high compression 2,4 or if you are OK with machining the cases for larger cylinders, go to a 92 or 93mm bore, and a 9.5 CR. The next step would be dual plugs and even higher CR.

I know a guy who has a 2,9 built on a 7R case with dual plugs. It is a real screamer.

The biggest decision, aside from the budget, is weather or not to bore the S case. Might be a better idea to just start with a 2,7 and save the S case.