KB's in a 318 with No Re-balance

aaronk785 said

My old bracket motor was a 440 with pistons 70 grams heavier than stock. No balance ran 11 years. Pulled the bearings and they looked like new so I reused them. Its setting in the corner of my garage for a back up motor. Ran its quickest times when I pulled it. high tens, low 11s. New motor is balanced cant see a difference in smoothness.

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And this I can see, and won't gainsay any of the experiences related about not balancing and engines working fine; I honestly believe all those stories. But if someone came on here and said they were putting in KB167's and did not mention re-balancing, then there would be all sorts of comments that is SHOULD be balanced.

So, which is it? Is balance important or not, and to what tolerance? I think this all is a testament that the actual effects of some level of imbalance are not all that well understood, at least at the hot-rodder level. All I know to go with is the wisdom and targets developed over years, that the harder you run and the higher you go in RPM, the more important it is and the tighter the balance tolerance needs to be. (Nothing new or earth-shaking in that statement LOL)