the MOST you can go is 89mm but even then the wall to the waterjacket is very thin..... I probably wouldn't go anymore than 87.5mm I dunno, depends on what you want.... if you're looking at getting bigger capacity then why not try a hybrid engine, get the 3T block (1800cc) and then pyut your 2tg head on it, it's not as easy as it sounds but it is pretty straight forward, if ya have any questions about it then just ask me, I have done this with my celica, the hybrid engine is really good...and ya dun have to worry bout getting boring done or custom oversize pistons either.