Harmonic Damper Bolt Kits As the crankshaft flexes and twists, the harmonic damper absorbs incredible amounts of kinetic energy. To ensure that the damper is locked in position, ARP has developed these ultra-strong 190,000 psi bolts that let you exert maximum clamping force. Special features include 1/4” thick, wide area washer and an extra tall 12-point head that accepts a deep socket and eliminates the worry of stripping the head.