We broke a lot of big block Mopars (383s, 400s & a few 440s) turning them a consistent 6,000 rpm in our dirt track cars. The motors were all stock bottom end, and lasted 8 weeks racing (about 3/4 of the season), they were plentiful and cheap, we were broke, I had a source that would sell me used big blocks for under $100 each. Spun rod bearings in most of them. We ruined a lot of good stuff back then. Gene