I have seen them split through the cam bores with a blower and no crank support at about 1000 hp.
Ok but can you rule out that it didn't happened because the engine was out of balance( harmonics) or detonation? Someone on this forum has to have pushed the block over 1000hp and made it live or is 1000 hp the limit to be on the safe side. Switching to an aluminum block is expensive.
