Mad Dart I have seen first hand stock blocks let go at 575 to 600 hp. The problem was the 4 bolt caps that were installed. I have no pics but worked at a reputable engine shop for 8 years and have seen the outer bolts would crack and brake the main webbing around the crank. I never seen any cap walk on a sbd but have seen it in sbc. But we did build a magnum block as a spare, left the stock caps on, arp studs. It made 585hp on the dyno and ended up getting use for a full season. When we tore it down for a freshening at the end of the season it was in perfect condition, very little cyl wear and the mains were exactly what they measured when the block went together and bearings looked new when disassembled. These engines were in late model circle track cars that lived at 7200 rpm. And the power was made with 2 brl carb.
