Adding the main caps caps probably helped with doomed block living a little longer.
You found the most common weak link in stock blocks - That is where they normally will crack - its a bummer but that's the gamble with a stock block.
If you remember Berraducci's hemi - that's the same deal that killed his .005 over stock stroke block. No warning just lost oil pressure one day.
I have had a couple do that - some say any detonation is the problem - some say a bad balance causes it. But I think its just the weak link in Big blocks.
