Jim Smart
March 1, 2007
Photos By: Benton Jackson

Balancing Act

Although dynamic balancing is optional (extra cost) with all engine builders, it is a necessity to engine smoothness and longevity. It is manda-tory at MCE Engines, but Marvin takes it a step further with his own disciplined approach to dynamic balancing. He weighs everything before it goes to Automotive Balancing, then AB precision balances everything to Marvin's own specs.

Dynamic balancing happens for the same reason we balance tires-to remove shake and vibration. Centrifugal force is an ugly thing when spinning and reciprocating parts are not in perfect balance. All pistons, rings, and bearings must weigh the same. Engine oil must also figure into this equation. Pistons and rings must weigh exactly the same as crankshaft counterweights. They should dance around each other smoothly, with the precision of a Swiss watch.

With dynamic balancing, each piston is machined down to the same weight as the lightest piston. Rings and pistons are weighed together as individual assemblies. All rods must weigh the same as the lightest one. To get it all in balance, remove metal from the heavier parts to get them down to the same weight as the lightest part. The same can be said for the crankshaft.

Internally balanced engines can be balanced independently of the harmonic balancer and flywheel/flexplate. Externally balanced engines, like the small-block {{{Ford}}} and FE-Series 428 Cobra Jet big-block, call for including the harmonic balancer and flywheel/flexplate in the balancing process.

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