As usual GM tried to execute a proven concept on the cheap. Competent water separation and particulate filtration wasn't provided, the pumps had low tolerance for bad fuel issues, so there was heat soak and sputter, engine not starting and so forth. Cut corners on the fasteners, which led to main bearing issues and head gasket popping. People have found when you spend some extra time and money reworking the fuel system and getting quality ARP main cap and head studs the engines actually will do well. There are a number of those engines running the roads right now after people corrected the issues GM failed to follow through on.