First, the individual parts are weight matched. These include the pistons, rods and rings. There is not much you can do to the rings or rod bearings so, other than just setting up the "File-Fit" rings before balancing, all you do is supply a single set for one piston (3-piece oil ring, second ring, top ing) to the shop doing your balancing. First all of the pistons are weighed, then all the rods, locating the lightest of each. At that point, if you are reducing the weight of these items, machining the lightest of each component first. You now match weight of the pistons and rods.

NOTE: "All" other component machining must be done BEFORE balancing is attempted...!


The RODS are matched as "small ends" and "big ends". This means you match all the "big ends" by hanging on a special hanging fixture, then you do the same with the small ends. Be sure to double-check!

The PISTONS are also weight-matched, but the "material removal" machining is done either under the piston pin boss with a special offset cutter, or it is done by drilling holes (very carefully) on the surface of the pin boss. You do this to both piston bosses, sharing the material loss. You DO NOT want to remove the material off only one side.

The Damper, Flywheel/Flexplate, Pressure Plate, etc. are individually spin balanced. Just like the wheels and tires on your car.

After you have completed this weight matching, you are now ready to mount the Crankshaft in a special Balancing Machine that spins the Crank with the Damper and Flywheel installed, as well as "Bobweights" that duplicate the compiled weight of the Pistons, Pins, Rods, Rings, Bearings, and a calculated "weight of oil". The crank is usually mounted in Teflon or Nylon "V-Blocks" on the Balancing Machine. The Balancing Machine measures "out-of-balance" through Computer-Controlled sensors. Just like the way your wheels are balanced when you have tires installed (or hopefully during normal maintenance as well), yet the engine balancing machine is much more accurate.

Any errors in the balance of the crank is corrected by either:
Drilling to remove weight
Welding to add weight
Machining and Adding "Heavy Metal" (Mallory Metal)
The Balancing Machine in many cases has a Milling Machine built on to it, making quick removal of material. The Milling occurs on the crank's counterbalances. If metal (weight) needs to be added, it in most cases is done within the existing balance holes in the crank. In other cases directly to surface of counterweights. In only extreme cases, typically with very lightweight design crankshafts, is Mallory Metal used.