I'm not sure the standard port size holds back a 512 inch engine. You should be able to make 700 hp with pump gas compression if you build a serious engine with solid roller cam and ported intake and stuff like that. If you want an 800 hp engine then yeah, the standard port size is going to hold it back but most guys are happy with 600 honest hp and a standard port window shouldn't have much trouble hitting that number even with out of the box parts.