clevite rod bearing

[Weekend Racer]

Thank very much for your good advice everybody. This help make the best decision

[carl hinkson]

Originally Posted by JRyan

I whole-heartedly agree with Carl & Reed that the two grams makes virtually no differnece. In fact, knats-*** balancing is highly overrated. For instance, you're in a circle track car turning left, do you balance the right side lighter than the left due to oil being thrown onto the right bank? Do you balance the rear lighter than the front due to loading the rear on acceleration? What about when you hit the brakes. In a
Formula 1 dry-sump world, pan efficiency might correct some of those issues, but in our world, we can only guess. Does your balance guy use one, two, or three percent overbalance? Does he really know what's correct 'cause the bearings might look good in all three cases?

Grumpy Jenkins used to put 70 gram heavier wrist pins in the race engines and put them on the dyno. When it came time to go racing, he put the light ones back in. If 70 grams per rod end weight didn't cause problems for the Grump, four grams per journal certainly won't. Don't worry about it.

Jerry

Back in the early 90's I worked the great Smokey Yunik on an engine development project and I asked him about balancing his exact words were ( Balancing is an IMPERFECT SCIENCE) I think that is an understatement to say the least.

[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

[BillK]

WR,
The 2 grams wont hurt a thing. Balancing is somewhat of a guessing game anyway. Can you tell me exactly how many grams of oil is on each piston as it goes up and down ? Like Reed said too, most guys will slightly overbalance any assembly that is going to be at high rpm anyway.

Originally Posted by carl hinkson

If you have the crank rebalanced once its done and the bob weights are removed have the machinist put the bob weights back on and see how close it is!!!

If he makes his bobweights correctly and puts them on the crank correctly, there should be no difference at all.

Hi Carl

[carl hinkson]

Originally Posted by BillK

WR,
The 2 grams wont hurt a thing. Balancing is somewhat of a guessing game anyway. Can you tell me exactly how many grams of oil is on each piston as it goes up and down ? Like Reed said too, most guys will slightly overbalance any assembly that is going to be at high rpm anyway.




If he makes his bobweights correctly and puts them on the crank correctly, there should be no difference at all.

Hi Carl

Hi Bill

Try that some time and you will see what I am talking about!!!!