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Old 11-26-2005, 09:20 AM
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To Balance or not????

So I have a 350 with a 400 crank reground to fit. The guy that ground it told me that the engine would not have to be rebalanced. I am using 5.7 PM Rods and keith black .100 pop up pistons. The Balancer is the stock balancer for a 400 and the pressure plate is balanced for a 400. Do I have to rebalance this assembly or will it be close enough??

Ric

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Old 11-26-2005, 09:26 AM
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Definitely balance it.
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Old 11-26-2005, 09:29 AM
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It must be rebalanced.
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Old 11-26-2005, 10:48 AM
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The chance of that combination not needing balancing is pretty slim. You may not feel an imbalance, but it doesn't take a lot to take a toll on main bearings, especially with a 400 crank.

tom
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Old 11-26-2005, 02:03 PM
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Quote:
Originally Posted by Ratchet
So I have a 350 with a 400 crank reground to fit. The guy that ground it told me that the engine would not have to be rebalanced. I am using 5.7 PM Rods and keith black .100 pop up pistons. The Balancer is the stock balancer for a 400 and the pressure plate is balanced for a 400. Do I have to rebalance this assembly or will it be close enough??

Ric

that guys full of crap!!! if you want it to last you better balance it. find another machinist, he sounds like ke doesn't know what he's doing, or he want's to charge you to regrind it a few months from now.
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Old 11-26-2005, 06:02 PM
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Quote:
Originally Posted by 406 ss monte
that guys full of crap!!! if you want it to last you better balance it. find another machinist, he sounds like ke doesn't know what he's doing, or he want's to charge you to regrind it a few months from now.
My sentiments exactly!
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Old 11-26-2005, 06:17 PM
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Definitely balance
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Old 11-26-2005, 06:31 PM
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im using a 400 block with the 400 crank but i used 350 rods and my machinist said you would be a fool to not balance it
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Old 11-26-2005, 06:45 PM
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Any hi-perf engine should be balanced....only makes sense
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Old 11-26-2005, 07:44 PM
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ANY engine i build gets a balance job, no matter what. small price to pay for the rewards it offers in longevity later..........i agree too, if your machinist said you don't need to rebalance it, take your business somewhere else........hell, i'll even rebalance a stock rebuild.................
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Old 11-26-2005, 08:43 PM
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The answer to your question, technically is maybe. If your bobweight of your new pistons and rods are close to the factory 400 bobweight, then you can get by without doing it, but..............

Since you are juggling from the stock 5.56" 400 rods, to 5.7's and going from a 4.125" diameter 400 piston to a 4" 350 piston, chances are that your new bobweight is going to be different from the stock 400 stuff.

Balancing an engine is not always necessary, but you really need to know a little about engine balancing to make a decision as to it's necessity.

My advice would be to get it balanced. Make sure you take in your balancer, flywheel and clutch assembly.

Brian
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Old 11-26-2005, 11:54 PM
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Here's my left handed approach....

If you can't afford $ 150 for a balance job, why build a performance engine??
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