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The most important issue is that the gear-drive in affect, physically ties the crankshaft to the camshaft. This transmits (in some cases amplifies) the crank harmonics into the valve train.
Remember, the lower cam gear is in-board of the damper, so every “pop and bang” goes right into the cam. This uncontrolled valve train motion results in inaccurate cylinder to cylinder timing, accelerated wear, part fatigue.
D-cel
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