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Old 04-17-2009, 07:00 AM   #1
Hyper
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Default How is the rotating assembly balanced?

I was looking for a good read that would explain the process of balancing the rotating assembly
I know the benefits, but I am really curious of what's involved

Is it worth to only do the crank if I am keeping stock STI rods and getting custom pistons?
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Old 04-17-2009, 09:24 AM   #2
Bamofo
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This is a good place to start.

http://www.fordmuscle.com/archives/2...mbly/index.php

If your using stock rods you will greatly benefit from balancing those alone. The pistons are normally within a gram if you use weisco but if you have a good scale you can get them to .1 gram. Since Subaru puts no effort into the 2.5 liter crank you might want to get that balanced too if your planning on doing over 8000rpm. But if your just looking to balance it for the heck of it rods and pistons is a really big improvement over not balanced.
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Old 04-17-2009, 09:39 AM   #3
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ah damm, I have to register there to view the other 2 pages

The pistons I am getting are Diamond, so they will be balanced for sure

So I can balance each segment on it's own, or it has to be made all together? ie, have crank machined at one shop while having the rods at another (because parts are in different countries )

Last edited by Hyper; 04-17-2009 at 10:11 AM.
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Old 04-17-2009, 05:28 PM   #4
Team Scream
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Quote:
Originally Posted by Hyper View Post
ah damm, I have to register there to view the other 2 pages

The pistons I am getting are Diamond, so they will be balanced for sure

So I can balance each segment on it's own, or it has to be made all together? ie, have crank machined at one shop while having the rods at another (because parts are in different countries )
Balancing the rods is simply making the big ends and the small ends all (each) weigh the same within a specified tolerance.

Your shop will take the lightest rod and make the rest weight the same at both ends.
Same with the pistons.....make them weigh the same amount.

Actually the crank, clutch and flywheel should be done at the same time because they are really the only things that get spun on a balancing system.

Rods and pistons you can do yourself with a scale and the proper jig for the rods as long as you know where it is safe to remove material and where you want to stay away from.
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Old 04-18-2009, 02:16 AM   #5
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understand now, thanks
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Old 04-18-2009, 12:24 PM   #6
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You take your crank, flywheel, clutch, rods and pistons to the machine shop. They way each piston and rod, then bolt the equivilent weight to the crank for each rod and piston on each location.
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Old 07-14-2009, 01:54 AM   #7
Hyper
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I'd like to bump this for a little more input

as Tilton clutch assemblies come balanced, would I have to include the flywheel to crank/rods/pistons if I wanted to have the crank balanced?
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Old 07-14-2009, 05:55 AM   #8
col5555
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Where do they commonly remove material from a piston??
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Old 07-16-2009, 12:46 PM   #9
bertune
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Quote:
Originally Posted by Team Scream View Post
Balancing the rods is simply making the big ends and the small ends all (each) weigh the same within a specified tolerance.

Your shop will take the lightest rod and make the rest weight the same at both ends.
Same with the pistons.....make them weigh the same amount.

Actually the crank, clutch and flywheel should be done at the same time because they are really the only things that get spun on a balancing system.

Rods and pistons you can do yourself with a scale and the proper jig for the rods as long as you know where it is safe to remove material and where you want to stay away from.
Pulley
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Old 07-16-2009, 08:01 PM   #10
madmax718
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crank pulley is pretty well balanced rotationally- a few grams here and there, but a stock one is hard to balance since its made with rubber- and as it degrades, it shifts around like a loose goose.

Scrap the pulley, go with a fluid filled..
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Old 07-17-2009, 11:56 AM   #11
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