[Reed Granrt]

This past winter, I got a chance to work with a very sensitive portable vibrometer. Since I am a consultant and sale balance machines, I wanted to try to duplicate track conditions. My purpose was to balance the internal components and then attach every thing else (distributor, water pump, belts, pulleys, etc)to the engine on the dyno and rebalance with all items spinning. I was going to attch shim weight to pulleys and or flywheel to correct. I calculated how long the motor would be in high gear and what the acceleration rate would be. Damn, I was so surprised at how much imbalance that I had that I called the company and they flew a person in to help me. We finally decided we had two imbalances. One was the imbalance of the rotating added assemblies and another imbalance of acceleration that need to be corrected with overbalance. As we tore the engine down, we inspected all the bearings and all looked well. We went back and finally found the old bearings that originally came out of the engine. All really looked pretty decent. No pounding. We overbalanced 1 % and that made no difference. Finally went to 4% overbalanced. Now I have heard many people tell me of HP gains they got thru balancing. During this time, I saw no discernible difference in HP. I did not have time to run a Six Sigma study to see if each was within workable tolerance, but it was minute differences. But the acceleration vibration was quite evident. I really believe I could have gone more than 4%. Our overbalance was based on 54% of the reciprocating weight and 100% of the rotating weight. But we had learned more than we thought necessary at that time as this was not the intent of the study. Remember, my intent was to balance all rotating bolt on assemblies. Oh yes we went back in and balanced the cam during one of these excursions. There are so many variables that can pop up in balancing CORRECTLY that I wanted to go the next step. Oh I almost forgot, during this test we had a vibration that kept showing up and we measured runout of the crank pulley end and it had a slight bend deflection as the rpm went up. I straightened the pulley end and balanced the crankshaft with out the balancer and then I installed the balancer and balanced the balancer. That problem solved.
reed