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Hi Guys. I thought I should post a picture and some text about a flywheel balancing jig I have for the V6 flywheel. This was used to balance the flywheel on my 2.5 after lightening and without pulling the whole engine apart.

Basically, you bolt this to the flywheel before lightening and get the balancers to balance the jig to the flywheel. Now the unit's got 0 balance factor. Then unbolt it and lighten the flywheel. When you're done take it back to the balancers and get them to balance the flywheel to the jig which gets you back to the original balance factor.

The flange is about 12mm thick and tapped to M12 X whatever pitch bolts used. For my 2.5, the radial strip is 20X70X6mm and the other strip at the end of it is 115X20X6mm. The distance between the centre of the shaft and the centre of the latter strip is about 80mm. Surface finish on the shaft is important for the balancers- this ones surface ground, fine finish turning should be ok too.

Scott
 

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Interesting...

And since the flywheel only goes on the crank one way, this balance jig only goes on the flywheel one way...?
 

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Interesting...
i second that!! looks very simple, but very effective! thankyou very much Scott for the info, i'll print it off tomorrow at work (my personal printer sucks) and take it to my engineer!
After reading the whole roxanne thread yesterday, i can't beleive alfa balance all these things individual with different flywheels pulleys etc
i don't disstrust what you say jj, iam sure the combo i have on my engine would be fine, but once that motor of mine is in the car and running.....:D
and knowing my luck if i leave it, ill end up with a vibration:mad:
 

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Discussion Starter #5
No worries Spence. Hopefully it's useful to your project. Some dimensions aren't critical, so yours doesn't have to be exactly the same but I'm sure you're machinist can figure it out. The main thing is that it balances up ok.

I'd be pretty amazed if Alfa balanced each motor individually as well. They'd have to assemble each front pulley, crank and flywheel. Then balance it, then disassemble it, and then assemble the motor with the correct pulley, crank and flywheel together. And all in mass production:eek:
 

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Have you ever watched that video of the 75 production line though? They were doing a hell of a lot of it all by hand.

ROCK ON
R~R
 

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In engine mass production it's only really practical to balance the components separately, marking the 'heavy' sides of the balanced components, then assembling them with the 'heavy' sides 180 out of phase to minimize the residual unbalance of the assembly.
 
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