I've heard the newer weightier cranks wont spin that fast. Or at least not for long.
None of them will last long at that RPM, but the fully counterweighted cranks are better for those high RPM applications. Our NHRA many time national record holding 292 powered Chevy II left the starting line between 10,500 RPM and 11,200 RPM and was shifted at 7200 with the fully counterweighted cranks, and the cranks lasted no more than (20)quarter mile passes before they broke. The forged cranks lasted fewer passes than that. We contacted Crower about making us a billet crank, and he said, "Save your money, because even a billet crank with the 120° firing sequences and damaging harmonics these engines have wont live long at those RPM's either!" Its doubtful your cylinder head will make HP about 6000 RPM to begin with, so trying to turn it 8000 RPM is an exercise in futility and a deep money pit as well as completely unnecessary to make good HP with of these engines.
