M42 Flywheel

[riverdale21]

I know you can put a 325i flywheel onto an M42 engine with the use of a 323 pilot bearing, 325 clutch, and 325 pinion gear in your starter (thank you Stu). What I want to know is if I wanted to utilize the stock M42 flywheel how light could I get it? And how much does the stock flywheel weigh?

[Rob]

stock is 27ish pounds I think. I also think lightening the stock fly would not be worth the effort

[///M42 sport]

you mean, don't do it unless you have to replace the clutch anyways.
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Motorcycle Tires

[Rob]

No, I mean I dont think it would be worth the effort to shave the stock flywheel down to the weight of a stock 325i flywheel, just doesnt seem worth it to me.

[e30Matt]

Can you even lighten a dual mass that far?

[Rob]

thats my point, you can only lighten OEM flywheels so far, and if you starting out with a heavy ass 27 pounder, you're not gaining much compared to a lightened 325i wheel at 11lpbs...

[fabianyee]

ARe you sure the 325i flywheel is 11lpbs, as in 11 pounds???

BTW, I have a single mass flywheel from a M40 (SOHC 8v) engine and it lightened. Estimated 1kg of metal shaved off the flywheel.

FYI, I replaced my M40 engine with the M42 from an E36 but retained my gearbox and flywheel.

[Low Level E30]

Just get an aftermarket flywheel for a 325i, and do the swap w/ all the other required parts. THAT would be worth your time, for sure - but perhaps costly?

Gotta pay to play.

[aaron_silva]

ARe you sure the 325i flywheel is 11lpbs, as in 11 pounds???

Rob didnt say a 325i flywheel...he said a LIGHTENED 325i flywheel.

Aaron

[riverdale21]

I can get an M10 flywheel for balls cheap. How much do they weigh stock and could it fit in my M42?

[demlotcrew]

From analysing the BMW ETK, I have found out that '89 models were fitted with the M40 9.973kg flywheel but were changed to a 11.45kg (aircon) or 12.25kg (no aircon) from 1990! So there's about 2.5kg saving to be had at a fraction of the cost of a performance part ! BTW, M20 engines have a 8.5kg or 9.98kg flywheel but will not match the M42 starter motor teeth, nor pressure plate, nor gearbox input shaft...and, if you fitted a M20 pressure plate you would be ~0.5kg up again (M40/M42=1.26kg, M20=1.674kg).

[riverdale21]

What about the M10 flywheel? Would that fit the M42 gearbox and engine?

[demlotcrew]

Sorry mate i really dont know if the M10 will fit, try it see what happens.

[fabianyee]

I weighed my lightened flywheel the other day and it's 7.7kg (~16.9 lbs)..
It's a stock M40 single mass fly wheel lightened about 2 years ago but I didn't get to weigh it before it went back onto the car..

[Stu]

M10 flywheel probably will not work because of the lack of reference sensor pins on the flywheel.

Lightening the dual-mass seems odd. The 325i flywheel is already 20 pounds, and can be shaved to 12-15 without problems. Plus you get to run the heavier duty 228mm clutch.