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Re: Balancing question for engine builders in here?
[Re: 40ford]
#244366
03/05/09 09:18 PM
03/05/09 09:18 PM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
They are correct! All you have is a very slight "overbalance" due to the lighter pistons. You didn't say what your bobweight is---probably in the 1600-1700 gram range. This 9 grams would be only 1/2% overbalance. Many high RPM engines use 1,2 or even 2 1/2% overbalance. Some shops overbalance 1% for everything but street engines.
What you don't want is an "underbalance" situation.
I dont remember the exact numbers but engine builder/tester David Vizard did some testing with overbalancing and found out there was free HP to be had. I think he found like 15 free HP by adding a slight overbalance on a 350 chevy. So like stated above mike
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Re: Balancing question for engine builders in here?
[Re: dOc …]
#244368
03/06/09 06:13 AM
03/06/09 06:13 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
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Posts: 52,972
Romeo MI
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Quote:
Has anyone actually checked weights of the pistons to see how close the shop has actually balanced them to "0" ? ....or whatever the shop claimes ?
A Bud of mine checked a well-known shop in the Detroit area ..... they claimed they balanced to 2 tenths. He weighed the pistons and some were off by almost 5 grams.
But some people claim that with all the oil flying around and on the rotating-assembly ....up to 10 grams off really does not matter.
Chrysler was the worst of the big 3 when it came to balance on the factory stock engines. Sure they will stay together but I'm a big believer in a good balance specially if you take it up in the revs. For you to feel it in the seat of your pants... its got to be BAD
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Re: Balancing question for engine builders in here?
[Re: Sport440]
#244369
08/16/09 12:43 AM
08/16/09 12:43 AM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
master
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master
Joined: Jan 2003
Posts: 6,591
Canton, Ohio
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Quote:
Quote:
They are correct! All you have is a very slight "overbalance" due to the lighter pistons. You didn't say what your bobweight is---probably in the 1600-1700 gram range. This 9 grams would be only 1/2% overbalance. Many high RPM engines use 1,2 or even 2 1/2% overbalance. Some shops overbalance 1% for everything but street engines.
What you don't want is an "underbalance" situation.
I dont remember the exact numbers but engine builder/tester David Vizard did some testing with overbalancing and found out there was free HP to be had. I think he found like 15 free HP by adding a slight overbalance on a 350 chevy. So like stated above mike
Found it for you RP, mike
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Re: Balancing question for engine builders in here?
[Re: a408swinger]
#244371
08/16/09 10:52 AM
08/16/09 10:52 AM
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Joined: Jan 2003
Posts: 16,932 NC
440Jim
I Live Here
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I Live Here
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Posts: 16,932
NC
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Don't stick those pistons in your engine, tell Ross to stick them... You ordered a certain weight and valve relief size, don't pay for anything less. If it is "OK" or not is not the right question. You didn't get what you ordered. Plain and simple. If you are thinking of accepting the pistons, ask for the cost of rebalancing the crank, plus shipping and handling... LOL
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Re: Balancing question for engine builders in here?
[Re: dOc …]
#244372
08/16/09 10:56 AM
08/16/09 10:56 AM
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Joined: Jan 2003
Posts: 16,932 NC
440Jim
I Live Here
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I Live Here
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Posts: 16,932
NC
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Quote:
Has anyone actually checked weights of the pistons to see how close the shop has actually balanced them to "0" ? ....or whatever the shop claimes ?
I check them before and after they balance them. My scale isn't as good as a good balance shop, but my measurements showed they all matched within the amount I can "read" on my scale (not claiming 1g accuracy).
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Re: Balancing question for engine builders in here?
[Re: 440Jim]
#244373
08/16/09 08:15 PM
08/16/09 08:15 PM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
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Posts: 6,591
Canton, Ohio
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Jim , what does the shop that you use, "as a rule of thumb" balance thier cranks to or otherwise thier accepted standard perimeters in reguards to 50%/even or 50%+ overbalance. 51% being equal to a 1% over balance. mike
Last edited by Sport440; 08/16/09 09:31 PM.
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