When car manufacturers developed fastener requirements for engines, the harmonic damper bolt was intended to merely secure the balancer, so a flat hex-headed design was typically employed. But in the world of high performance, the balancer bolt gets quite a workout on account of needing to turn the engine over manually to set the timing, adjust valve lash, etc. This often results in the bolt head becoming “rounded off” from heavy use — sometimes to the extreme extent where wrenching is virtually impossible.
A worn-out hex-head damper bolt compared to a new ARP bolt. ARP’s damper bolts come with a large 1/4-inch thick washer to better distribute the clamping load, and a packet of ARP Ultra-Torque fastener lubricant to ensure proper preloading.
That’s why the engineering team at ARP focused its energy on developing the “ultimate” balancer bolt. A tall 12-point head is employed to facilitate the use of a deep socket for increased contact area. No worries about rounding the bolt head with this design, whether through repetitive use or high fastening torque loads. The company also offers an alternative damper bolt that’s designed to accommodate a standard 1/2-inch square drive allowing the use of a large ratchet wrench or breaker bar to turn the engine over. The outside of the bolt is still a large hex. Topping it all off, ARP balancer bolts come with a large diameter, 1/4-inch thick washer that optimizes distribution of the clamping load.
ARP has multiple options for many applications between a large hex bolt machined to accommodate a 1/2-inch square drive or a deep 12-point socket. Both designs hold up better to constant had-rotation of the engine than standard bolt designs.
ARP’s balancer bolts are manufactured from a premium quality nickel-chrome-moly steel alloy and precision heat-treated to 190,000 psi nominal tensile strength — substantially stronger than OEM hardware. Moreover, ARP’s damper bolts are reusable, while most factory fasteners are torque to yield, and should NEVER be re-used.
ARP rolls threads post heat treat, for the strongest threads possible.
Another important attribute of ARP’s balancer bolts is that threads are rolled after the heat-treating process, as opposed to the more common cutting of thread. The threads are formed to SAE AS8879D specifications, which assures optimum engagement with the crank snout. All these features combined result in a fatigue life of up to ten times better than ordinary fasteners….
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