hunting M42's

[Tom D]

its been a while, but evan and i finally got together, rolled up our sleeves and got to work. well he did the work and i supervised.

what we started out with was a M42 from a 1992 OBD1 E36, we used the block and head. the cylinders were round and straight, but the ring ends were out of spec so new rings went in. the main and rod bearings were spot on, but we added new rod bearings for a tighter clearance and higher oil pressure. the head needed nothing, but got a skim for a bump in compression.


to that we added an E30 intake, oil pan and AC pump. we also installed the new timing stuff we found in an earlier scavenger hunt.

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then we took one 1983 G240 transmission and one 1991 G240 transmission and grafted them together.



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giving us this..... a G240 trans with a M42 bell housing and a E21 speedometer drive.

[sbcrockett]

man I wish you were my neighbor, Tom. great work and thanks for sharing the pics

[mjweimer]

This is a great thread - can't wait to see pics and details on the front subframe mods as well as the rear trans mounts.

[Tom D]

we are probably gonna pull the M10 this week, anybody in the bay area interested in it?

[Hagbard]

Hey Tom, why did you want to use an M42 for your son's car and not the M44? I know the M44 is bigger and quieter than the M42 right? Will the M44 not fit in the E21 engine bay?

[SoCalE21]

Would be very interested in the M10 if we could get it down to So Cal.

[Tom D]

the M44 is the same engine with some differences, like the M42 uses hydraulic buckets under cam and the M44 uses hydraulic rams under rocker arms. mainly however, is the M44 is an OBD2 engine and doesn't appear to be easily converted to OBD1.

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Would be very interested in the M10 if we could get it down to So Cal.

free M10 to anyone that wants to pick it up.

[SoCalE21]

Dang!

[dups]

Question:
Why not just use all e30 parts? Engine and transmission, of course.
We get a lot of m42/44's around Florida; eventually hoping to go this route.

[Tom D]

i explained that in the first part of the thread.

[dups]

Yeah, I re-read it now. Thanks.

[Tom D]

we weighed the M10 drivetrain today, this was complete from engine to trans and everything in between.

a 4:1 class two lever and a low tech scale equals



457 lbs. plus or minus

[dups]

Is that a 1.8 m10?

[Tom D]

it is, along with a g245

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engine's in

[bflan2001]

Man you work fast!

[Tom D]

this weekend evan and i finished the drivetrain by installing the driveshaft. because the E21 uses u-joints it is important that the transmission, differential and the driveshaft are all at the correct angles. most driveline specialist agree that the working angle of the u-joint should be between 0.5º and 3.5º and the sum of both joint's angle should not exceed 1.0º

we started by establishing a straight-line between the front crank bolt and the pinion nut. we used this line to locate the center of the transmission output flange and the driveshaft center bearing.





then we measured the pinion angle, it was 2.7º up. using this number as our baseline we set the angle of the engine/trans at 2.7º down. after that we made new mounts for the center bearing being careful to keep it's axis on line with the crankshaft/transmission.



with all the fabrication done we bolted everything down and took our final measurements.
the objective was to get 0.0ºs of un-canceled driveline angles, we got 0.3º, well within the acceptable 1.0º

[DavidD123]

That's quite the view to wrench on cars from!

[MortyCrock]

That's quite the view to wrench on cars from!

Holy crap, that IS a great view! Great work on the driveline, guys!

[bflan2001]

Assuming this wasn't done with my car, am I pretty much hosed since all the fabrication is already done?

[sbcrockett]

that first picture is epic! what an awesome place to work on cars!

[WantingAfunE21]

Assuming this wasn't done with my car, am I pretty much hosed since all the fabrication is already done?

You may be able to shim the Engine/Transmission mounts to help with the angle if it is out of spec.

[Tom D]

That's quite the view to wrench on cars from!

sometimes life leads you down wonderful paths.... this is the view from my shower.



and most evenings end in a high note.

Assuming this wasn't done with my car, am I pretty much hosed since all the fabrication is already done?

brian, you should be okay, you'll just need to do some shimming. note that we have lowered the transmission mount to get the angle for the engine/trans and most likely you'll need to lower your center bearing mount as well.



the problem is that a u-joint does not rotate in a circle but rather an oval, the greater the angle the bigger the sine wave. i have developed a pinion bearing noise in my E21 and I'm pretty sure it is because i didn't cancel out all of the u-joint oscillations, causing too much side force on the bearing.

[HipMF]

If I lay on the ground behind my car and look at the driveshaft I can see that it's nowhere near straight. The front of the engine is about 1.5 inches too low, and the center support bearing is noticably offset to one side. Drove 12000 mile this past summer with no noticable issues. I intend to fix it this winter... if I have time... but it nothing worth losing sleep over.

Edit: My driveshaft came out of an e30 with over 200k on the clock and all I did was wire wheel some of the rust off and hit it with a spray bomb. In the process, I lost the paint dots to line up the front and rear halves, so no clue whether it's balanced anymore either...

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So you're using an e21 driveshaft on this swap? How does the length work out that way? I was under the impression that the e21 driveshaft was too long.

Also, any idea whether the e21 CSB will fit on an e30 driveshaft? Since the e21 is offset to one side relative to the monting holes (whereas the e30 CSB is centered), it might be an easy band-aid fix for my mounting brackets not being in the right place...

[Tom D]

no we're using an E30 shaft . the E30 center bearing is also off center.

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I can see that my driveshaft is nowhere near straight.... but it nothing worth losing sleep over....

thats good, but maybe not the advice you want to give other people. our driveshaft is not straight either, as i stated above the engine is at -2.7º and the pinion is +2.7º. what that translates to is .566" of fall (or rise) per foot of run and since the output and the pinion are both pointing in different directions the driveline is far from straight. the reason for the string line is to keep the driveline straight from side to side, if it isn't then you have compound angles and the math gets even harder.

as i mentioned above, i have developed a pinion bearing whine in my swapped E21, I'm pretty sure its because i didn't get the shaft as close as we did this one and that is why we chose to do it right this time. the whine didn't happen right away, but took about 20K miles. you can also trash the ujoints, the center bearing, the guibo, or the transmission, not to mention having the shaft come apart because you exceed the critical speed of the shaft.

[amarino]

sometimes life leads you down wonderful paths.... this is the view from my shower.



and most evenings end in a high note.

You're in San Jose, right? Where do you get a view like this?