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Old 12-05-2006, 09:27 PM
ARW ARW is offline
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Balancing question - I must be confused.

I finally ordered a rotating assembly, balanced before shipping, from a reputable shop. Having balancing done out here in the boondocks requires a 400 mile round trip to a good machine shop. Well, the pistons just showed up from one coast still in the wrappers, never touched. The crank and rods will come from the other coast, apparently later. I sort of thought you had to weigh the pistons and rings individually and make up bob weights and maybe assign each piston a hole. There are no weights or locations marked on these pistons. If you just take the published weight and never see even the pistons, can that still be a properly balanced rotating assembly? Are manufacturing tolerances that good these days? (these are 496 forged) Your good advice may save me from chewing on somebody unfairly. Thanks.

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Old 12-06-2006, 07:40 AM
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Quote:
Originally Posted by ARW
I finally ordered a rotating assembly, balanced before shipping, from a reputable shop. Having balancing done out here in the boondocks requires a 400 mile round trip to a good machine shop. Well, the pistons just showed up from one coast still in the wrappers, never touched. The crank and rods will come from the other coast, apparently later. I sort of thought you had to weigh the pistons and rings individually and make up bob weights and maybe assign each piston a hole. There are no weights or locations marked on these pistons. If you just take the published weight and never see even the pistons, can that still be a properly balanced rotating assembly? Are manufacturing tolerances that good these days? (these are 496 forged) Your good advice may save me from chewing on somebody unfairly. Thanks.
I would have it checked as we have seen some of those magazine balance jobs and there tolerances and the ones at our shop differ quite a bit.
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Old 12-06-2006, 07:58 AM
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Quote:
Originally Posted by ARW
I finally ordered a rotating assembly, balanced before shipping, from a reputable shop. Having balancing done out here in the boondocks requires a 400 mile round trip to a good machine shop. Well, the pistons just showed up from one coast still in the wrappers, never touched. The crank and rods will come from the other coast, apparently later. I sort of thought you had to weigh the pistons and rings individually and make up bob weights and maybe assign each piston a hole. There are no weights or locations marked on these pistons. If you just take the published weight and never see even the pistons, can that still be a properly balanced rotating assembly? Are manufacturing tolerances that good these days? (these are 496 forged) Your good advice may save me from chewing on somebody unfairly. Thanks.
If you bought a rotator and everything is still in the box you will find the big end of the rods are on the tight side as the pin end of the rod is on the tight side and a area that is always over looked is the pin bores in the pistons will be on the tight side as they sell these assemblies ready to assemble as from what we have seen they are far from that.

And on most of these kits we end up going with a over size rod and main bearing.

We have seen on some rods that the pins will not even go through the rod with out hoing them.

Have things checked out so don;t have to do the job twice.
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Old 12-06-2006, 08:39 AM
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'Ya know...I am an Old Fart but I still shy away from kits.

I would rather know exactly the vendor the parts are coming from and depend upon an honest reliable machine shop (machinist) to do the machining. I will do final check and assembly.

Crate engines are a big no-no to me.

JUNKYARD DAWG
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Old 12-06-2006, 01:29 PM
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I don't think you can get an accurately job by using published figures on parts that aren't at the actual balancing shop. I have seen "balanced assemblies that were over 30 grams out when checked on our machine (Hines HC500).

tom
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Old 12-06-2006, 06:54 PM
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First, it probably is technically balanced, by design weight. That is the way most production engines are balanced. There are +/- weights parameters and it is probably "balanced" to the middle ground. Pretty much the way factory engines are produced. They also have stock assemblies balanced for racing so they are not quite that accurate. HOWEVER... in a "custom" suppposedly balanced addembly, that is unacceptable. I would likely check all the weights and see how close they are. I can't recall what my balancer tolerances are, but a call to the shop,even 400 miles away, would give you the tolerances they balance to. Now remember, that you need to match up the heaviest and lightest together to get the separate cylinders as close as possible, that's the way it is done prior to balancing. If they are so close that there is no difference, I think you would be lucky. Again, I don't know how they can do it like that but it wouldn't be impossible, they would have to be ordering from a place that will match pistons/rods up to their weight designation... It my be something you can do. I still prefer the old fashioned way.
Old Fart too

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Old 12-06-2006, 08:45 PM
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ALSO AN OLD FART!!

The only way the assembly can be truly "Balanced" is to have all the components gathered together and weighed. Then the crank/bobs spun up. If you read the fine print on some of these guys "Balanced" assemblys. It will say within 30-50 gram. You are paying them the same price that a good 1/2 gram balance job costs! We also Hines balance..
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Old 12-07-2006, 08:57 PM
ARW ARW is offline
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Thanks for the advice guys. I'm sure I can't change the "deal" already made, but now I know I need to go get it balanced again when it gets here. And maybe someone else will read this and shop smarter than I did.
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Old 12-08-2006, 10:16 AM
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Don't know where in TX you are located, but I just used a shop in Denton,TX that balanced my assembly to "0". I'm in the process of assembling it and everything is going together real well. The shop is called Precision Engine in Denton, TX, owner is Wayne Calvert, a google search will give you the phone number. He has a lot of Bonneville experience and does a lot of hot rod stuff here in North Texas. Shop ain't real big but it was real clean and organized. I'll sure use them again.
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