rankshafts are the core of the engine. Because of that, they should, by all accounts be rock solid. Although they're regularly viewed as an unyielding, immovable object, in reality, that's not the case. The crankshaft twists and bends relative to the loads placed upon it by the respective pistons and rods on each throw. In testing by an industry giant, General Motors have shown that the crank in a 350 cubic inch small block prepped for racing can deflect considerably at 8,000 RPM. There's more too. A crankshaft also has natural frequencies. Coupled with the frequency of the torque inputs and resonance, severe crankshaft vibrations can result. What happens next? Outright crankshaft failure if a damper of some sort isn't used to still these vibrations. It wasn't that long ago that one found aluminum hubs on the nose of a drag race engine. Bad idea. The end result was often a multiple piece crank.

A label you'll want to see on an aftermarket damper is this
SFI Specification tag. According to the NHRA Rule Book, certified
dampers are mandated in many classes of competition.
Why? Simple. Some OE dampers are prone to self-destruction,
particularly if they're old or worn out.


We're not quite done yet. There's more here than outright crankshaft carnage. When harmful crank vibrations aren't kept in check, then valve timing can be disturbed (often
dramatically), wet sump oil pump gears can shatter, oil pump drive shafts can break, timing chains can stretch and self-destruct and shifting gears in a stick shift combination can become impossible, or at the very least, decidedly difficult. Main bearing wear is common when the vibes aren't controlled. Quite regularly the thrust surface of the main bearing shows signs of major degradation. Evidence of main cap to block fretting, chafing, or galling is also common. Rod bolts can continually loosen. Ditto for little things like valve cover bolts. Rod bearings can blacken. Valve spring life can become dismal. Flywheel and converter bolts can loosen. Flywheels can physically break. The torque converter pilot or hub to gear surface can fret or chafe. In general, plenty of ugly things can happen due to bad vibes.

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