1977 2.7 911 barrel upgrade
 

just rebuilding my porsche 2.7lt motor just wondering wat are the maximum sized pistons and barrell i can use without machining the case thanks

Opening up the spigots on a 2.7 mag case is not really an option. There is very little metal between the opening and the head studs. You can go to 92mm and I think possible even 93mm (without modifying the case) however the cylinder walls get very thin.