The Balancing Act – Why you should balance your Engine

An engine is a precise machine. Its performance and efficiency depends on the proper coordination of its internal components. If one these components break, then the engine is rendered helpless. It cannot function normally even with the slightest breakdown of one of those parts.

In racecar’s engine, where huge amount of power is generated, vibrations can beat up the engine internals. A balanced engine is necessary to avoid serious damage and power loss.


Even if engines were balanced when they came out of the factory, changing components may alter that balance. The original engine balance is normally affected with changes in pistons, rods and cranks. Though some replacement parts are lighter than the stock parts, the difference in weight whether lower or higher, still causes imbalance.

Benefits of engine balance include lowered stress value, and lesser vibrations. For the race driver, this is translated as better performance.

Crankshafts can be overbalanced. This is done mainly to minimize vibrations generated by high rev engines. High rev engines can cause severe vibrations that can crack other engine parts due to fatigue.

The objective of engine balance is to alter some components to make sure severe vibrations will only occur when engine is running lower or higher than the normal range of operation.

Engine 2

In engine balancing, it is crucial for the weight of pistons and connecting rods to match. They are physically weighed, but separately. However, most aftermarket performance parts are already weighted and matched.

Putting more weight or reducing weight on some areas of the crankshaft is how you can balance it. By adding metal slugs to drilled holes on counterweights of the crank will make it heavier without altering the size of the crank.

Ends of the crank’s counterweight are drilled to create holes that will reduce its weight. Another method to lessen the crank’s weight is by machining the ends of the counterweight, which will lessen the outer portion of the crank.

With the crankshaft, piston assembly, and rods balanced, the engine is now internally balanced. However, an engine can also be externally balanced. This procedure now involves the flywheel and harmonic damper. Both these components are attached to the crank while it is being balance on a machine. This time, the crank will not be touched in any way, but in order to get a balance, weights are added to either of the two components- flywheel or damper.

External balancing is not normally used in racing due to the fact that if anyone of the damper or flywheel needs replacement, the whole engine will have to be replaced.

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  1. [...] wrong. There is a whole website dedicated to car tuning, and there’s some info there about engine balancing. Turns out that a properly balanced engine reduces vibrations, and thereby improve [...]

  2. Eric says:


    Thanks for the post. I couldn’t agree with you more….