An externally balanced 4.00" stroke crankshaft used in a 454 and 502ci big-block Chevrolet engine requires a counterweighted damper for proper engine balance. This harmonic balancer is used with LS-6 and LS-7 engine assemblies. Technical Notes: Use with crankshafts P/N 3963523-4 and chromed timing pointer P/N 12342001.