M42 single mass VS M20 single mass conversion

[dude8383]

Is this worth stickying btw?

i can easily do that but would have to get approval from ALL of the mods.

[JoeDellio]

I always read through these flywheel/clutch threads but dont know what parts to get, you guys seem to all be 30's and I have an e36 M42, I dont konw what applies and what doesnt. Plus I have A/C and I see that mentioned as well.

I would like to just get a M42 flywheel and grind it down, I would like to keep the starter stock. With the M42 single mass flywheel ground down you can still use the M42 clutch? Or could I upgrade to another pressure plate? I was wondering how the M42 clutch fork function was affected by grinding a good part of the flywheel away.

Or, if I were to actually shell out $600 for a M42 LW FW and I could use M42 stock clutch, which one would I use, the Dual mass clutch or single mass clutch? Im all disoriented now.

[redhead]

dual mass flywheel needs a dual mass clutch, ditto with the single mass. They are not interchangeable.

[JoeDellio]

Just for the record, a late model M20 starter will bolt right up... no need to change pinion gears.

Not to bring it up from the dead, but will it bolt up to the E36 gearbox? And what year are you considering a "late" model 325? My M20 starter is out of an 88.

[KenC]

Not to bring it up from the dead, but will it bolt up to the E36 gearbox? And what year are you considering a "late" model 325? My M20 starter is out of an 88.

I don't know if it will bolt up to the e36 gearbox. Is it different than the e30 one?  My starter came off of a 1990 M20.

[autox320]

I'm leaning toward the single mass M42 option, but have a couple questions.

If I go the single mass non-ac M42 flywheel, and single mass non-ac clutch M42 kit, will I need different bolts for the flywheel?

[dude8383]

I decided to Sticky this, lots of good info here.

[DesktopDave]

I'm wondering about this myself.  I was figuring the non-A/C setup would be the perfect solution.  I'll be waiting until my clutch gives up the ghost though.

[colin86325]

If I go the single mass non-ac M42 flywheel, and single mass non-ac clutch M42 kit, will I need different bolts for the flywheel?

Yes.

[Bracky]

Is this in reference to a E30 323i or E21 & I'm guessing either way its still the same 323i TOB? As for the clutch does it have to be for a 323 or could a 325 clutch be used as im guessing the 323i has single mass where as the 325 has dual so clutchs would not be interchangeable?

I have a ltw 323i flywheel that weighs roughly 11lbs.

I paid less for the whole deal that the M20 clutch kit.

This by far is the best option because the flywheel is lighter than ALL three you've mentioned. Not sure about cost or availability but I got lucky with my purchase.

323i Flywheel : $75
323i TOB: $63
M20 Clutch: $100


ZERO chatter with this setup.

[DesktopDave]

I wasn't sure about that.  The e30 323i never came stateside, we got the 325i instead.   I assumed that it was the e21 323i or the similar e21 320i/6.

[harvey2]

I believe the reference is to the same parts I'm using.  I've got the parts here in my hands right now:
 
SM Flywheel from 1979 euro 323i E21 (M20)     11 22 1 264 517
clutch disk for 1990 325i;                      21 21 1 223 174 (BavAuto)
pressure plate for 1990 325i;                 21 21 1 223 026 (BavAuto)
T.O. B. to fit 'E21 323i;                        21 51 1 204 525 (BavAuto)

The pressure plate, disk and flywheel fit together perfectly.  As for fit into the car, a few days will tell.  The only open question is the need for a flywheel-to-crank spacer.  We will measure and see but I believe I can leave it out.  I think the TOB was used for several years and spans E21 and some E30. BMWFans shows this TOB being used up to March '84 in the Euro E30 323i.

Here are the other parts I'm using for my 1991 318is flywheel conversion:

flywheel bolt 28mmlong 11 22 1 717 840
pressure plate bolt 07 11 9 901 023
slave cylinder 21 52 1 116 300
alignment tool BavAuto CA83 (see note below, yours may vary)
pilot bearing 11 21 1 720 310 (BavAuto) (see note below, yours may vary)
rear engine seal 11 14 1 706 785 (BavAuto)
locating dowel 11 11 1 743 118 (Pelican)
exhaust gasket 18 30 1 711 969 (Pelican)
exhaust nuts 18 30 1 737 774 (Pelican)
Starter from 1989 325iX (Bosch), rebuilt

I'm not sure why the previous poster claimed his flywheel was 11 lbs.  Perhaps this was an estimate, or perhaps it has been lightened, but I weighed my flywheel and it came in at 13.6 lbs not including any bolts or spacers.  After resurfacing I weighed it again and it is now 13.4 lbs.  

There is a metal spacer that came with the flywheel ((pn 11 22 1 262 827).  On the E21 it was between the bolt heads and the flywheel (also shown on realOEM/BMWfans diagrams). I note that many photos of M20 flywheel conversions into 318s show that installers don't include this spacer.  I'm not sure why not, since it is a standard part used with all M20 SM flywheels as far as I can tell.   I will re-use that spacer as well in my installation.  It affects the depth to which the flywheel bolts penetrate, so is worth a mention.
 
Update:  it turns out that the pilot bearing listed above (plus alignment tool) was wrong for my car.  Further study of BMWfans shows that the Getrag 240 transmission input shaft diameter changed in Sept '90 production from small (12mm) to large (15mm).  I bought the 15mm one (above) but in fact should have got the 12 mm one:  11-21-1-709-681    Your requirement will depend on production date.

update: the rear engine seal mentioned in the parts list above did not get used for two reasons.  The mechanic did not trust the part delivered as he was not familiar with the brand, plus it turns out my rear main seal was not leaking after all.  It was transmission oil that was splashed all over the place and dripping onto my garage floor.  What a mess, on the clutch too.  Transmission sent out for repair.

[DesktopDave]

Keep us posted...I'm unsure what I have going on in there, but I'll be sure to check this out when mine taps out.

[Bracky]

Kl its nice to know im not on my own with this I've PM'd "dude8383" to see if he can shed some light. Even 13.4lbs is still alot lighter than the m20 unit and should make for a good revvy base in an e30 as I done the M20 conversion to an E36 about a year ago and even on the much larger car it was very noticeable.
Also some people have been saying that the later 325i starter will fit without modification which i did not find to work last time, I think it was from a 1990/91 so does anyone have any more info on this or part numbers??

[harvey2]

Kl its nice to know im not on my own with this I've PM'd "dude8383" to see if he can shed some light. Even 13.4lbs is still alot lighter than the m20 unit and should make for a good revvy base in an e30 as I done the M20 conversion to an E36 about a year ago and even on the much larger car it was very noticeable.
Also some people have been saying that the later 325i starter will fit without modification which i did not find to work last time, I think it was from a 1990/91 so does anyone have any more info on this or part numbers??

I've been told that without question the M20 starter just bolts right in, however with all things the devil may be in the details.  I have found one poster who claimed it must be a Bosch brand starter.  It seems that in the US we mostly see the Bosch starter but there have been other brands used so fitment may vary.  I was also told the starter had to be from a late model 325 (experience quoted was from 90 or 91).  The BMW pn for the starter hasn't changed from 87 to 91 (per BMWFans), but who knows if this is dead accurate.  

I thought previously that the difference in starters had to do with electrical hookup, not mechanical fit.  Yours is the first comment I've seen that mechanical fit was an issue.

I received assistance from KenCopperwheat and dude8383 in sourcing the right parts.