How They Make It: Vector DamperDuring the firing stroke, each piston and rod assembly can exert more than a ton of downward force on its corresponding crankshaft rod journal. That much force causes the crankshaft to bend and twist, generating high-frequency harmonics that make the crank vibrate like a giant tuning fork. If left uncontrolled, this vibration may result in crankshaft breakage. The job of a harmonic balancer (aka the vibration damper) is to absorb or tune-out these bad vibes.
Stock-style dampers consist of a heavy inner sleeve and an outer inertia ring separated by a rubber ring. The inertia and rubber rings operate like a big spring, setting up a damping action on the crankshaft as it tries to twist and untwist. Unfortunately, over time, the rubber ring may deteriorate, causing delamination and separation between the inner sleeve and inertia ring. Even when functioning as intended, an elastomer balancer has a relatively narrow range of maximum damping effectiveness that's not optimized for typical hot-rod engines.
Naturally, the aftermarket has stepped up with superior damping technology. One leading outfit is Fisher Concepts, makers of SFI-legal Vector Dampers. The Vector's multipiece, modular design operates kind of like a radial shock absorber to cushion crankshaft vibrations. Instead of using a rubber elastomer ring or hydraulic oil as found on some competitive designs, Vectors have mechanical friction elements under tension that permit fine-tuning the damper for greater effectiveness over a wider rpm range. The multipiece unit can be easily rebuilt, and the modular configuration lends itself to quick production of one-off specials. Whether it's a mainstream domestic V-8 or a weird car, motorcycle, or even (gasp) import, Vector can make it! -Marlan Davis