2.0l M42 Info and Build Thread

[Dave_M3]

Interesting stuff!!!

I might have to make up something similar too when I start building a 2.1 so looking forward to seeing how this turns out

[odbod]

Right so we're mking some progress at last, in the next couple of weeks
I'm getting 2 cranks machined so they are a direct fit in the M42 Block etc with the nose modified so it is the same as an M42 crank front end. We're getting a 88mm and 89.6mm stroke rover crank done, the nose mods aren't an adaptor, it's a properly fitted modification, I doubt you will be able to tell how it's been done and it'll drive anything, including a SC if you want it to...

There is opportunity to do more at the same time and cost, but got to be quick it shoudl be happening v soon, maybe even next week....

pm me, or post if anyone wants in.

Anyone want a 2.0 or 2.1 crank for reasonable money?

[odbod]

Now 3 cranks going through, any more takers? this should be a low hassle reasonable cost route. Supply a Rover type crank (cheaper than the BMW ones) and £200 and get a straight fit 88 or 90mm stroke crank!

[rix313]

You got your cop plate fitted yet?

[thetomc]

Right then, in anticipation of the modified cranks showing up sometime soon I have finalised my build spec for the bottom end.
In summary, 90mm throw crank, 135mm rods, standard m42 bottom end and standard m42 psitons gives me a 2 litre bottom end with an 11:1 compression ratio. Nice!

Please feel free to check my working;



Tom

[appletree]

The one thing i would consider is the rod length, i dont know what length the rods are in the M47 enigne but when i was looking in to doing a 2.1 rotrex build the engine builder said that to drop the rod length down to 135 wouldnt be a very good idea and infact he said if anything he would have increased the rod length.

this was all in a FI build though so guess it might not be so important on a NA build, the theory behind it was that when the the crank was at 90degrees to the cylinder through its cycle with a larger throw of the crank and a smaller rod your making it hard work for the conrod shells and small end bearing to be pulled at that angle and this could increase the were on the sides of the pistons and the walls as with the smaller rods trying to pull the piston over as they cant keep up with the angles the cranks asking them to go at meaning the grudgen pin has got to turn more in the small end bush aswell = more wear

I know the above isnt very technical but it would be much easyer to explaine with a picture

Don't know what rod length Tim_s used (have a feeling it waas standard 140mm ones) but i know he had small end issuses and maybe this contributed to it he also had a slight score on one of the cyliders while running the new build in, it could have been just a running in problem but its just a thought.

[thetomc]

I agree with all of that. The steeper rod angle will make for more wear and friction. Whether that will come back to haunt this engine i don't know yet.

(Max rod angle increases from 16.8 to 19.5)

I'm guess this has been covered elsewhere but does anyone know the rod length and crank stroke for the hartge m42?

[appletree]

This was the only pic i knew of that had any info on the H2.1 and H2.3 youve probly seen it though.

http://media.photobucket.com/image/hart ... hartge.jpg



What do Metric merchnics use on there 2.1 out of intrest??

[appletree]

Just looked and it seams to be 138mm page 18 of the link below.

http://www.metricmechanic.com/pdfs/metr ... ooklet.pdf

[tim_s]

many months later i know, i've not been playing e30s much. rod length is pros and cons really. You can get nice big valve pockets and have a decent amount of top ring to deck clearance (great for FI engines), on the flipside it'll increase piston speed by quite a bit so not good for high rpm, as well as the increased rod angle/bore wear etc.
Sadly m42 doesn't really have the block height to pull off good rod ratio as well as long stroke. mine runs 140s and custom pistons which is pretty good though, lovely jubbly. I run just over 11:1, although have just lopped another lot off the cyl head so should be a bit higher now
As for my escapades/screw ups, little end bushes were just bad machining by machine shop, score on bore was just a ring hanging on fitting. I'm actually on a 1.9 at the mo until I can be bothered to get another set of rings, fresh bored/honed block etc to repair the slight mark on the bore on cyl 2 that was causing a bit of oil usage. want to get a little bit over the 200bhp mark on standard inlet, was at just about 200bhp on the dot last time. Not sure what I'll be changing to get there, though! Would help if i wasn't distracted by my e46 330 wrongness, playing with my bro's m3 evo, and considering series 1 RST wrongness as a toy e30 is being well behaved and not warranting any attention

I'm not sure I really like the threaded bits on the crank nose. I take it you're getting the cranks balanced again afterwards?

[Dave_M3]

Good to see you still tinkering with the M42s Tim!!!

I thought you were about to give up when you were selling off all the stroker bits a few months ago

[thetomc]

Yep the whole bottom end will be going off for a hefty weight reduction and a full balancing before xmas. £300 which i think is pretty damn good.

I've got access to suitable measuring equipment at work to get the fine tolerances on ring gaps, running clearance (piston-skirt to bore), bearing sizes (which colour code to use) etc so i'm hoping to get a very solid build completed for the bottom end.

Going to use m20 flywheel again, trimmed down to 11lbs. I've been running this mod on my current setup for well over a year now with no problems.

Head will be stock initially. Exhaust manifold will be stock e30 m42 into a custom free flowing system. Inlet is already mocked up on my desk with e36 m3 throttle bodies and massive tapered trumpets . Management is most likely going to be Omex.

Once i've got all that running sweet i'll look towards some head work if i'm not making the power i want.

The work that has been done modding the nose of the crank is impressively well done by a very respectable company. I'm very confident it won't be a problem. (Fingers crossed!!)

Edit: One more thing to add is that i'm not going to be making an 'NA Screamer' with this setup. I'll most likely be keeping the rev limit to 6.5/6.75. Its the torque i'm going after with this build and i think it should deliver well.

[tim_s]

Good to see you still tinkering with the M42s Tim!!!

I thought you were about to give up when you were selling off all the stroker bits a few months ago

Yeah i was a bit, stuck the 1.9 in and had done with it. The 1.9 is a 1998 block, 50k miles, out of an auto etc, and I got it cheap so couldn't say no! Stuck in some new gen bm big end shells (complete waste of time, the origs were basically brand new!) and away I went. I needed some time off I figure. Am ready to go with it again now though! Need to find another block and order some rings! Shouldn't take long to put it all together, she's got long mot (straight through other than sticky brake light switch) and tax, new tyres etc so nothing else needs attention.


As for the stroker 2l, sounds like it will be a nice engine.

Be interesting to see what compression numbers standard pistons but with the higher CR give...

The 2.1 pulls 210-5psi with cams (would prob be a bit higher on standard cams). my high-ish CR m44 on same head/cams/HG as the 2.1 does a nice healthy 175psi across the board, and i get 180psi on the 330.

[rix313]

Did you end up fitting the lower guide inplace of the sproket? What was involved with doing it if so? Just buy the guide and swap it over? or was the timing case different with an extra threaded hole?

[tim_s]

Did you end up fitting the lower guide inplace of the sproket? What was involved with doing it if so? Just buy the guide and swap it over? or was the timing case different with an extra threaded hole?

the cases are different, both front and rear pieces.

[appletree]

So did you never sell your old 2.1 set up in the end tim??

[tim_s]

So did you never sell your old 2.1 set up in the end tim??

nah by some happy circumstance i was way too busy with work commitments and stuff to actually bother selling any of the stuff, and now feel ok with getting it all going again! Worked out pretty well really Just need to bore and hone another block, pop some new rings in and then i can drop the engine back in. how's yours?

[sg_frost]

do you have any piccies of the modified crank that I can have a squint at, I have now got a rover 88mm crank to be modded. Thanks

[sg_frost]

I'm now building one of these with a rover 75 diesel crank. Does anyone have any piccies of how to modify the nose?

[tim_s]

I'm now building one of these with a rover 75 diesel crank. Does anyone have any piccies of how to modify the nose?

It's described quite well in this thread, you can also look on MM's site, they appear to have done the same and have pics. can see that rover cranks are cheap and available, but still think proper bm ones that fit are the way forward. spose i would say that as I'm running one

[Dave_M3]

Friend of mine thinks he might have two M47 cranks sourced so he'll give me one if I'll do the machining needed for his one while doing mine

[odbod]

The guys that did the cranks for me machined up a few (3-4) extra front end parts for doing some more rover ones, but delivery wa really slow, still worth pursuing though if people want more done.