Factory harmonic damper bolts are an area of concern for racers and performance enthusiasts for two reasons. First is the bolt’s ability to sustain the necessary clamping force when subjected to high RPM crankshaft flexing and twisting. A second consideration is the extra abuse that comes from rotating the crank manually when adjusting valve lash, setting timing, etc. This often results in the bolt head getting “rounded off” to the point where wrenching is compromised. Noted fastener manufacturer ARP has addressed these problems and offers a pair of solutions.
First is a special 12-point bolt that’s designed to be used with a deep socket and offered for a variety of domestic and import engines. Also available for many popular applications is a large hex-headed bolt that is forged to accommodate a standard 1/2” square drive breaker bar or ratchet wrench.
Both are manufactured from a premium grade 8740 chrome moly steel and heat-treated in-house to provide a nominal tensile strength of 190,000 psi. A large diameter 1/4” thick washer is included to help distribute the load over a wide area, while the bolts and washers are black oxide finished for extra protection.
For additional information visit www.ARP-bolts.com. A free printed catalog that details 5,000-plus fasteners is available upon request. Personalized tech assistance can be obtained by calling 800-826-3045.