All I know is that I have turned a balanced STOCK bottom end with STOCK heads with a MP 284/484 cam 6500 on NOS, drove it 80 miles round trip on 4.56 gears to the track for 8 years before putting in a 493 stroker. Motor ran great when pulled and is ready to run still in another car if needed. A lot depends on the builder, the matching of parts and proper maintenance.