[4b] A harmonic balancer bolt that wasn’t quite tightened to the factory spec (160 ft-lb) allowed the balancer to walk on the keyway. That motion had left the crankshaft and its keyway in very poor condition. The key literally fell out of the crankshaft upon removing the timing set, and that revealed significant damage to the crankshaft keyway slot. It meant that our 455 H.O. needed a new crankshaft, and a complete engine rebuild was in order.