how to balance engine - Team Camaro Tech
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post #1 of 6 (permalink) Old Aug 27th, 03, 06:57 AM Thread Starter
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I'm trying to figure out how I'm gonna build my short block and my question is on the balancing, do I send the rods, pistons, crank, flexplate, etc to the machine shop and they balance the whole thing or do I just buy wieght matched rods, pistons and just send the crank to the machine shop or can I buy a crank that is already balanced? Also are there performance levels of balancing, ie do I ask for it to be balanced up to a certain rpm or runout?

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LS1/T56->1969 Camaro
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post #2 of 6 (permalink) Old Aug 27th, 03, 08:31 AM
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You need to give the balancer guy all the parts. He will first weight match all the parts, then put simulated bob weights on the crank and match the counterweights to the rest of the assembly. He will take into account some subjective considerations such as the weight of the oil on the parts but basicaly, there is no need for any other specifications from you. My balancing guy gets about $125 if I remember correctly but I have heard of $250 with the clutch etc included.

-Mark.
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post #3 of 6 (permalink) Old Aug 28th, 03, 01:44 AM
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Industry standard, I believe, is 1/2 gram [email protected] rpm. Meaning when the weighted assembly, everything Mark suggested to give the balancer, is rotating at 2500 rpm, the accellerometers are telling the operator the amount of unbalance in weight.

The money spent for a good balnce job is well worth the investment. Keep the balance card in a safe AND rememberable place for future replacement of parts.

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post #4 of 6 (permalink) Old Aug 28th, 03, 03:13 AM
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If you are planning on really buzzing it a lot, go with a 52% overbalance, as it will smooth things out at higher rpms. That said, I would have to hunt a while to find it, but there was a tech article on how GM used the same crank with about four or five different piston/rod combos in OEM applications with the same balance work on it. You would be surprised to know how much imbalance there is in most engines. One time I had to throw a race motor together in a day after finding a machinist misunderstood my instructions on decking the pistons. I had two different brands/weights of pistons in the motor, it was the only way I was able to get to Dallas and race! Plus I got down to three cars, so it was worth the thrash. I did take it apart and do it right once I came home though!

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post #5 of 6 (permalink) Old Aug 28th, 03, 07:18 AM Thread Starter
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Thanks for the advice. I kinda thought balancing was important which is why I was thinking along the lines of weight matching all the parts myself to +/- 0.1 grams and just buying a balanced crank, but it sounds like I need to weight match the parts and then send them to the balancer, the problem is trying to find a good balancer that I can take the parts to and trust he will do half as good a job balancing as I will weight matching. I envy you guys back east, you seem to have a lot more resources for this type of work.

thanks again
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post #6 of 6 (permalink) Old Aug 29th, 03, 02:08 AM
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Static balancing the parts isn't a bad idea, but, the balancer will have to do it again to get the bobweight for the crank so he can dynamic balance the assembly.

It would be like the difference between bubble balancing the front tires and spin balancing them on the car, a world of difference.

Search the Yellow pages and ask around from friends and neighbors for a shop, and fellow rodders. When you find them, ask them the specs they balance. Usually, the shop with a crankshaft straightener does balancing as well.

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