Hey guys, I see lots of good examples of split 5.0 blocks from some unexplained phenomenon at some undetermined and apparently variable level of horsepower. I'm probably pretty close to the informal 500 crank-hp "limit" myself so the backup plan is probably a Dart block. Some say it's RPM-related, some boost-related, some think certain castings are more prone than others. The only thing I've noticed (analyzing every picture I can find online, I've not seen one in-person) that seems fairly consistent is that the cracking is universally in the lifter valley, in some cases (like the sticky on this forum) resulting in a cam that cracked in half -- or, resulting from a cam that cracked in half. I've seen very few cases where the cracking seems to originate at the crank, and girdles are reported to have almost no effect. So my question is... for those who've managed to split their block, what kind of cam / springs were you running? Understanding I have a very limited sampling-base available, your feedback would be helpful. My hypothesis is that heavy springs or above-stock lift / rocker ratio is the best indicator of potential block failure and NOT horsepower or RPM. Horsepower is correlated and not a causal factor (i.e. those making 500 horsepower probably run an above-stock cam). Hoping to put some predictive structure and simple engineering analysis to this fairly common problem by posting this question broadly with the goal of providing more than just loose guidance for the blocks' limits and trying to understand the most destructive forces by analyzing existing failures (as I have neither time nor resources to properly test the hypothesis). Thanks!