Have you ever wondered what that spinning steel ring on the front of your engine’s crankshaft actually does? We’re here to tell you that it does more than simply hold your accessory drive pulley to the engine. That rubber mounted ring is there to keep your engine from coming apart. A rotating crankshaft will tend to act as a torsional spring as the forces imparted against it when each cylinder fires, try to force the crankshaft to rotate backwards. When the pressure from the firing cylinder is released, the crankshaft untwists. This is when vibrations occur. At certain engine rpm, these actions can synchronize with the vibrations in the crankshaft, resulting in resonance. This resonance amplifies the crankshaft’s vibrations, causing extreme stress that can even result in outright crankshaft failure.
Elastomer harmonic dampers have been used exclusively by car manufacturers for years. The reason is simple, they have found that a tuned elastomer damper is able to reduce crankshaft-breaking harmonics more effectively and over a wider range of engine rpm than other styles of dampers.
Now that we understand what a damper actually does, do you know which one your engine needs? Will an OE damper work, or should a performance damper be used? That’s not a question with a simple cut-and-dried answer. While we are certain that an OE damper can and does do a satisfactory job of reducing harmonic vibrations in stock applications, at what point is OE not sufficient? If your engine will be used only as a daily driver, then an OE damper should be fine. But, if you know that your engine will –even if only on occasion, see the upper limit of engine rpm, then an aftermarket damper like one from ATI should be considered. You can check out an article about custom ATI dampers here.
Since the typical OE-style damper has an inertia ring with a rubber insulator that is pressed to the crankshaft hub, after time, this inertia ring can move in relation to the hub when the elastomer starts to wear out. During the life of a damper, the rubber can deteriorate from exposure to oil, varying temperatures, and mechanical fatigue. When this deterioration occurs, even if the inertia weight doesn’t fly off, this movement of the ring can at a minimum, cause the timing marks to move in relation to the crankshaft keyway. That makes it tough or nearly impossible to properly time the engine. That in itself is another good reason to upgrade.
Several years ago, a company called Katech conducted a harmonic damper test for General Motors. Katech is well known in the areas of engine design, prototyping, testing, R&D, manufacturing, and vehicle modifications. The test involved the use of four different aftermarket dampers on a 427ci small block. From 3,112 to approximately 6,500 rpm, all of the dampers limited crankshaft twist to no more than 0.6 degrees. Above 6,500 rpm, crankshaft flex increased with three of the dampers. At 7,893 rpm, one damper allowed a considerable 2.0 degrees of crankshaft twist. The second had 1.7 degrees of twist, and the third had approximately 1.25 degrees of twist. The last damper tested was made by ATI, and allowed just 0.28 degrees of crankshaft twist. The reduction in twisting motion makes the ATI damper a must-have for any engine.
So whether you have an engine that is mostly stock, or a maxed-out race monster, choosing a damper requires more than just looking at price. Think of it this way, you have just spent $8,000 or more on the engine in your ride. Are you ready to pay that a second time when that stock OE damper comes apart? Buying a new, aftermarket damper like one from ATI might seem like an unnecessary expense, until you experience failure—which was avoidable.