[Green993]

Alfonso, Haven't done anything yet. Will contact Costa Mesa and see what they say. My case is on its way back from Ollies so I have to get to this soon. I saw the video you mentioned - it was for a Chevy crank.

Originally Posted by AlfonsoR

Perhaps too late, but the 50% vs 100% sounds like a general design rule. I searched too, but could not find any info. I would recommend you contact a couple of race shops and ask them what spec they use for balancing their cranks. It might be beyond what you need, but it more than likely will be a spec that allows x amount of imbalance. Come to think of it, Costa Mesa R&D has a video on balancing cranks. They would be able to help you with a spec for your crank.

In machines such as compressors and steam turbines, it is a fairly common practice to balance rotors to 4 x W / N, where W is the weight and N is the max run speed. This calculation will be in oz-in. This is essentially an Navy spec. It may be of some guidance. You can read more here: http://www.irdbalancing.com/downloads/shoptolerances.pdf

What did you end up doing?

P.S.: found a site that explains it better than I did and it is focused on cranks....Balancing Machines by CWT Industries - Why Balance Crankshafts, Cranks, and Line Hones?

Notice that their computer screen shows two balance planes, which means they are assuming for the purposes of balancing and correcting weight that the rotor is supported by two bearings, one at each end. So to apply the above formula, W is the weight at each end or essentially half of the total weight. The oz-in value is the max allowable in-balance. The balance software will calculate that for you and tell you at what angle the imbalance is so that if there is a correction needed you know where to add or remove weight. Anyway, probably clear as mud now.