Replacing Dual Mass Flywheel - balancing?

[Erik]

My ZR-1 came with a billet flywheel from Carolina Clutch. I'd like to replace that with an original dual mass flywheel. I've read some comments that the original flywheels were balanced to the engine at the factory. As I'd likely be getting a good used one, does it need to be balanced to the engine? How is that done?

What's a good match in terms of a smooth engaging clutch disc to go with it?

[DRM500RUBYZR-1]

Erik,
When we change them, I send both flywheels to my machine shop.
We mark the one removed to indicate its position in relation to the crank.
We then ask the machine shop to match balance the new to the old, and marking the new with the same mark form the old.
Maybe not the most precise way, but it has served us well.
Hope that helps!
:cheers:
Marty

[Erik]

Erik,
When we change them, I send both flywheels to my machine shop.
We mark the one removed to indicate its position in relation to the crank.
We then ask the machine shop to match balance the new to the old, and marking the new with the same mark form the old.
Maybe not the most precise way, but it has served us well.
Hope that helps!
:cheers:
Marty

Thank you, sir.
But will that work with the non-stock flywheel I currently have?

[DRM500RUBYZR-1]

While the weight of each will certainly differ, their balance should end up closely the same.
:cheers:
Marty

[A26B]

While the weight of each will certainly differ, their balance should end up closely the same.
:cheers:
Marty

Marty, This may be true, but I think it is highly unlikely that the previous owner who installed the aftermarket flywheel rebalanced anything. The LT5 is internally balanced and the DMF is zero balanced. It should be just a bolt in swap.

If the SMF was not zero balanced properly, then to copy any imbalance would be duplicating the error, if any.

[Jagdpanzer]

My understanding is the the LT5 was assembled with pistons, rods, and crankshaft that were produced with very tight production weight tolerances which facilitated the low vibration level specification the engine is known for. However, if during factory dyno testing an engine was found to exceed the strict vibration limits they would bring it into compliance by trim balancing which involved inserting small balancing weights into the holes drilled in the outer edge of flywheel or front damper or both depending on the readings coming from vibration test equipment connected to the running engine at the time.
The DM flywheel and front damper are otherwise neutral balanced if no trim weights are have been inserted.



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[Erik]

My understanding is the the LT5 was assembled with pistons, rods, and crankshaft that were produced with very tight production weight tolerances which facilitated the low vibration level specification the engine is known for. However, if during factory dyno testing an engine was found to exceed the strict vibration limits they would bring it into compliance by trim balancing which involved inserting small balancing weights into the holes drilled in the outer edge of flywheel or front damper or both depending on the readings coming from vibration test equipment connected to the running engine at the time.
The DM flywheel and front damper are otherwise neutral balanced if no trim weights are have been inserted.



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Thanks, Phil.
I was wondering about that. So how do you work around it? Or is it just a matter of accepting a bit of vibration?

[Jagdpanzer]

Depends how within tolerance your engine was when it was first tested.
For example the original engine in my 94 did not have any trim balance weights in either the DM flywheel or front damper so changing to another neutral balanced flywheel did not influence the vibration level.
My guess is the typical production LT5 that required trim balancing was still better balanced than the typical V8 anyone in Detroit was producing at the time.



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[grahambehan]

Well, Phil is correct, when in the LT5 is internally balance, with neutral, or zero, balanced dampner and flywheel. When in the dyno room, but not on the dyno, per se, the balance was checked with accelerometers attached to the engine where it had to be within 1/2 maybe 1/4 ounce inch. If it exceeded these limits weights were added where neccessary. The majority of 90-92 engines had some weight, although not all. The 93 up engines, typically did not need rectification. So when replacing the dmfw or dampner it was recommended to remove the weights from the original parts and add them to the replacement parts. So if your car has an aftermarket fw, chances are that was neutral/ zero balance. If you do not have a "perceived" balance issue now, you should not have an issue with a replacement.

Graham

[Erik]

Well, Phil is correct, when in the LT5 is internally balance, with neutral, or zero, balanced dampner and flywheel. When in the dyno room, but not on the dyno, per se, the balance was checked with accelerometers attached to the engine where it had to be within 1/2 ounce inch. If it exceeded these limits weights were added where neccessary. The majority of 90-92 engines had some weight, although not all. The 93 up engines, typically did not need rectification. So when replacing the dmfw or dampner it was recommended to remove the weights from the original parts and add them to the replacement parts. So if your car has an aftermarket fw, chances are that was neutral/ zero balance. If you do not have a "perceived" balance issue now, you should not have an issue with a replacement.

Graham

Thanks, Graham.
So if I get a flywheel with some weights on it, just remove them and use as is?

Otherwise, they only other option is to pull the engine and balance it out of the car? If one was wanting to make it perfect.

Btw, what changed in 93 to make them better balanced?

[grahambehan]

First, yes if you buy a Stock dmfw that has been used. If you find NOS, there will be no weights added. Second for the 93 design we were looking to reduce reciprocating mass, the rods were lightened by extra machine work, which reduced the variation from the previously " as forged" areas.

[Perry Mitchell]

I find this very interesting. I will have to check the original dual mass flywheel/clutch/ pressure plate that I have on the shelf to see what configuration it was from the factory. I removed it from my '91 LT5 when I switched to an automatic trans.