We had 1 guy years ago, that ran a 412 in a super gas car. The factory block cracked, and was un-usable. So, by them Dart had blocks available. We used a new Dart block, and he wanted to stay at 4.125 bore, basicaly standard. His old block was 4.185. Obviously new pistons were used, but they were the same Je piston, except for a 4.125 bore, otherwise, all his old parts went back in. Engine went from 685 hp, to 650hp. .060 over in that case was 35hp.
Other good examples, are big block chevy's, from a 540 to a 565, no other change, your talking 35-40+hp there too. 25 cubic inch, is a lot, and its all from increasing bore size. Part of the gain is from unshrouding from the bigger bore, plus the added cubic inch. Do the math. If you have a given combo making say 850hp, at 540 cubic inch, thats 1.57hp per cubic inch. Now, add 25 cubic inches, and simply multiply 565 times 1.57 and you get 887, thats 37hp. And that is a common gain, from just the bore size on those engines. But again, your gaining a lot of cubes.
Frank
Advanced Performance
www.get-ap.com