Should new clutch package be balanced?

[Frankr]

2.7 RS clone motor finally needs new clutch after 25 years. Should new clutch and existing flywheel be re-balanced or let sleeping dogs lie?

[Chuck Miller]

When I did my motor rebuild in '03 we sent the clutch and flywheel in with the rest of the usual balance stuff...

Not sure about just the clutch, but if you were to resurface the flywheel, then I'd send'm both in...

My 02

[Silverbullit]

You might look into having it "match balanced". This process balances the new pieces to the old, under the assumption that the old parts balancing was fine.

[chris_seven]

I think that the way we balance bottom end assemblies is interesting and much of what we need to do will depend to the history of the engine.

I would expect that a 911 crank have been reasonably well balanced and Porsche specify a maximum out of balance.

The next question is how well the flywheel we bolt on has been balanced and how it has been corrected.

With steel flywheels that are machined well the out of balance forces could be very small and with a modern CNC could well be within acceptable limits without any further work.

If the flywheel has been component balanced it is likely to have been centered on an accurate mandrel so it runs true.

As long as it has minimal run out when bolted to the crank it could well be good it could be good enough and by measuring the run out it should be quite easy to decide if it needs more work.

If the flywheel and crank have been balanced as an assembly and corrected by drilling the flywheel then it will need re-balancing when the flywheel is changed.

Clutches are more problematic.

Hoffmann make a range of clutch balancing machines and production clutches are quite liklely to be well balanced - particularly Sachs, LUK and the like.

Again the issue is likely to be run out due to the mounting holes in the flywheel,

I must say that if I had a stock flywheel wit a good face and a replacement Sachs or Kennedy clutch I don't think I would be too worried.

If you fit an Aluminium Clutch as a replacement it will be of less concern as it is a lighter assembly.

[Frankr]

Thanks. Using stock replacement Sachs clutch and original steel flywheel. Was always very smooth to redline.