M20 flywheel conversion

[fresh_TD]

For you guys that have done the M20 flywheel conversion, did you guys source individual used parts, or did you get a kit from somewhere? It almost seems like the cost would be around the same as if you just bought an M42 aluminum flywheel(9lbs) from JB racing ($630) and it doesn't require any modification.

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[ccsdo5]

an M20 fly wheel doesn't need modification to work with the M42. Here's why I am running and some rough pricing for ya

- M20 single mass flywheel $100
- resurface flywheel at machine shop $70
- spacer ring from m42 dual mass flywheel (already had)
- stock m20 clutch and pressure plate $250 new? not entirely sure
- m42 TOB (already had)
- m20 starter $50
- m42 slave cylinder (already had)

That was the way I went and that is definitely cheaper than $630 plus you have all the M20 clutch options, whenever mine decides to go from abuse I'll be putting in a stronger six puck clutch.

[fresh_TD]

Thanks for the info.. I know I said "modifying"..what I meant was having to buy all these additional parts to make the conversion work if you go the M20 route..but looks like the savings are a couple hundred bucks, which is significant

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[Vanilla Gorilla]

I put the pieces together over about a year when I was able to find a decent piece for a good price.

I got an m20 starter that was used for maybe 400 miles for $25
13lb 323 Flywheel was $100 used
$60 to resurface it locally
Drilled the spacer ring from the m42 flywheel
New flywheel bolts were $4 a piece from Bav Auto.
Sach's replacement clutch/pressure plate was $180
323 TOB $60 through a friend who's works in parts at local BMW dealer
Most people don't mention this but all bmw single mass flywheels have a washer/spacer ring that goes under the flywheel bolts. It looks exactly like the spacer you need to drill off the m42 flywheel.

I'm pretty sure it is to stop the bolts from messing up the flywheel surface when your torque them. Some people run it, some don't. I ran it on mine and my buddy had one around he gave me for free.

Best upgrade I have done to the car yet. I can actually overtake people in 5th gear now on the highway lol

[benz-tech]

I personally don't like the idea of putting a spacer between the flywheel and crank. I don't feel its an accurate enough coupling, IMO. That said, if you lighten the flywheel by removing the material that would otherwise hit the block, there is no need for the spacer in between. The bolts need one of course. I did use the longer 323i t/o bearing. Its a fantastic upgrade for sure. 12.5lbs and I could have gone lighter.
aAnd just run the entire late m20 starter. Its so much easier than swapping rings yada yada yada. Cranks a lot faster too.

[TobyB]

There is a TSB from BMW back in the M10 days that says that the spacer between the bolt
heads and the flywheel is because they stopped hardening the metal around the holes
and if you omit the spacer, the bolt heads may sink into the flywheel and it will loosen!!

I looked at the stack of M10 flywheels I had after I read that, and sure as shit,
a few showed no signs of hardening, while on most it was quite obvious.

And a hardened and ground spacer, used properly, will work just fine for this sort of thing.
That is to say, yes, you really can't make your own out of some leftover sheetmetal you found
in the autobody dumpster...

t

[Vanilla Gorilla]

There is a TSB from BMW back in the M10 days that says that the spacer between the bolt
heads and the flywheel is because they stopped hardening the metal around the holes
and if you omit the spacer, the bolt heads may sink into the flywheel and it will loosen!!

t

Yikes!!!! That makes me really happy that I used it on my car!!