Originally posted by camaro_fever68
A two bolt block is strong enough to handle anything under 450HP/450 ft.lbs. in the 6500 and below RPM range. The 4-bolt was designed for heavy towing to keep the crank from walking side to side at low rpm. I read of a test where a engine was built just to test a stock GM block. It had all forged internals and was put on a dyno. It was a 2-bolt main. The base HP was 512 @5800 and torque was 460 @4400. They started off with a 250 shot of N2O and did three pulls then increased to by 150hp shots doing three pulls each until at over 1200 HP the engine cracked down both sides in the lifter valley. No problem with the 2-bolt mains. If they were super weak, I think that would have been the first place to break.

I am by no way saying a 4-bolt is not a better block, just that a 2-bolt is not junk. If I built a 2-bolt over 350hp I would splay the three center mains just like the 2-bolt 400 blocks.
that was the point I was trying to make, but it didnt come across as well as you have explained it. thanks