Budget M42 turbo build

[gearheadE30]

Been doing a bit of work the last few days :)

[gearheadE30]

Forgot about the bolts; oops. Added to the list.

[e30guydownunder]

I used:

E30 323i Single Mass flywheel
3mm Spacer between flywheel and crank
E30 323i starter pinion modded to fit in M42 starter (not direct plug and play like late M20 starter pinion)
Single mass clutch kit including the M20 TO bearing that came with it.

Don't forget the single mass flywheel bolts to suit.

[gearheadE30]

Here's what I used:

-M20b25 single mass flywheel
-late M20 small starter, i think only from the m20b25
-e21 323i throwout bearing
-M20b25 clutch kit
-The back side of the flywheel needs to be machined down so it is flat in order for it to clear the back of the engine
-M20 flywheel bolts

The starter is pretty easy to take apart, and you just have to swap the back half of the M20 starter into the front half (mounting points) of the M42 starter.

Also, got a new trans on the way! hopefully this one works out better....

I really think that's it...

[Schnitzer318is]

Schnitzer, What more info do you want about the M20 swap?

A list of exactly what is needed. I am always reading different things about different throwout bearings and pinion gears that made me now want to swap.

Also, I thought it was better to have a heavier flywheel with a boosted application to help load up the turbo and get faster spool? I could be wrong, just thought I read that somewhere...

Keep up the good work gearhead... you'll love the boost. Will make all the work, and ducket spending worth it.

[gearheadE30]

Thanks :). Yeah, the budget is a bit more than I expected, and I estimated high, hah. It'll be worth it, though.

Small little update: now planning on using a Valvo 740 TIC intercooler. More surface area and thinner core, and a lot easier to mount, I think.

[Hobbes]

Reading this thread made me happy. I always want to keep my m42, but I don't think I have the budget to go FI. Though I will say, Megasquirt and boost does sound like a ton of fun, and m50's are heavy.

[gearheadE30]

so I finally got the trans in, and what do I find? No third gear and a completely shot 4th gear synchro. Wonderful. At least the flywheel works great. And just for reference, even though the M42 and late M20 starter look the same, they aren't. You still have to swap over the pinion gears.

[e30guydownunder]

Does the M3 flywheel fit int he e30 getrag 240? I thought the bell housing was too small.

Nope and the mods the PO did to the bellhousing to make it fit are scary! I'm using a 260 in my build so won't be an issue.

[gearheadE30]

Does the M3 flywheel fit int he e30 getrag 240? I thought the bell housing was too small.

At any rate, its almost back together. I just have to bolt the trans, starter, driveshaft, heatshield, and exhaust back in :)

[e30guydownunder]

teh 228% has a 6% increase in Surface Area over the 215, but as the area is also further out, this should boost its torque capacity even further. But as you said upgrades are plenty available.

I picked up a 240mm M3 clutch/flywheel kit inadvertently with an M42 purchase. I was happy!

Making some nice progress there.

Schnitzer, What more info do you want about the M20 swap?

[gearheadE30]

haha well I suppose I'll find out soon enough. Even if it doesn't work out, though, there are a lot more upgraded options out there for the M20 than the M42, at least that I could find.

Also, the M42 actually came with 2 different versions of the Getrag 240. The gear ratios are the same between the two, but later ones got a 15mm pilot bearing (up from 12mm) and a slightly different shift mechanism. I'm not sure if there are any other differences though.

[Schnitzer318is]

Now you got me all excited...

Hopefully that added diameter will grab as you said. I'm interested as I've wanted to do an m20 conversion but hadn't been able to find as much info as I wanted on it. I've driven a car with the conversion done though and it was nice.

[gearheadE30]

Pics of some of the progress, in no particular order:

[gearheadE30]

Well, hopefully it will...228 mm vs 215mm makes a pretty big difference because of the diameter of the friction material. At a glance, the 325i PP looks a bit wider, but I'll measure it later to confirm.

Weight differences:
M42 FW-28.8 lbs
M42 clutch assembly-38.5 lbs

M20 FW-lightened to 16 lbs
M20 assembly-30.4 lbs.

The difference is reasonably large, and all said and done, it only cost me $400 worth of parts, machining included. There also appears to be a lot less mass on the outer edge of the M20 FW than the M42 dual mass, so that's probly going to make a bit of a difference as well. It should all be installed by sunday if all goes well

EDIT: the friction material on both pressure plates is 3.5cm wide