Harmonic Balancer - Holes for external balancing?

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Hi guys, If a harmonic balancer has holes drilled into one side at the factory, would this suggest the engine is externally balanced? And would this mean that harmonic balancers are not interchangeable?
 
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4,177
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I have used balancers from junk yards and never had a vibration. The diameter of the crank sleeve which the balancer mounts is too small in diameter to really equate in the balancing process. So my guess would be the balancers would already have been balanced before installation.
 
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over yonder
Externally balanced engines typically have the weights on the flywheel or flexplate. Harmonic balancers are there to dampen any vibrations that balancing did not take out. They don't actually balance the crankshaft weight like one might infer from the name. Holes in harmonic balancers are typically used for putting a tool on that keeps the balancer and crankshaft from spinning when installing the crankshaft bolt.
 
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Originally Posted by Spetz
Hi guys, If a harmonic balancer has holes drilled into one side at the factory, would this suggest the engine is externally balanced? And would this mean that harmonic balancers are not interchangeable?
No and No Technically, the word "balancer" is accurate by the dictionary definition but misleading by the industrial definition of balancer. The automotive harmonic balancer is more accurately described as a, inertially induced displacement damper. (an orbiting shock absorber) "Balancing" in terms of rotor body is the axis alignment of a center of geometry with a center of mass so "balancing" to whatever standard is RPM specific ( and can be affected by thermal growth) and a process of alignment, geometric considerations and mass adjustment (addition or removal of weight) and in some applications the additional considerations of fluid dynamics external to the machine. In terms of that- the harmonic balancer simply takes various vibrations induced from rods, engine geometry, timing, displacement etc. and "blends" ( harmonizes) then with whatever rubber or fluid method it uses to "smooth" things out. Given what they do and how they work, as long as you have an ISO interference fit, they will work adequately because in spite of all the articles written, its virtually impossible to balance and maintain an ICE to any recognized balancing standard. Even if you achieve it statically, it is unlikely to hold dynamically as RPM increases due to the operating properties of cranks and rods along with combustion energy. The best that can be achieved is precision machining for alignment and fit with very careful gram weighing and truing to equalize the weight of the parts. (which does make a significant difference when done properly)
 
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