Author Topic: E36 M42 engine rebuild factory specs? (Read 12637 times)

wannam42 · « **on:** December 21, 2009, 08:54:41 AM »

I'm planning to do a full rebuild of an M42 from an E36. Does anyone have a list of specs / tolerances for the machine shop to follow?

The E36 Bentley manual lists some but it's for the head and it may not even be complete. I don't have the Haynes.

I've read on this forum that the E36 and E30 M42s do not share the same set of piston rings. I'm not sure what else is different. :confused:

Can anyone help me?

longtallsally · « **Reply #1 on:** December 25, 2009, 06:45:56 PM »

Ooooh. I wanna know some of this too as I'd eventually like to rebuild my engine, or swap in one that I've rebuilt.

BlueBMW · « **Reply #2 on:** December 26, 2009, 09:41:52 AM »

Here's what I've gathered from the technical data I have access to. This is for an E36 318is coupe with an M42b18 (US Spec of course) Hope this helps

wannam42 · « **Reply #3 on:** December 30, 2009, 11:20:24 PM »

Many thanks BlueBMW! I can't understand half of it though.

What does the +0.014 mean in the bore dimensions?

Did I read it right that valve guides aren't replaceable for the E36 M42?

The conrod bearing journals have a +0.009 and a +0.025 notation. What does this mean?

The piston-to-wall clearance is 0.01 - 0.04mm? That's 0.00039 inches! So what does the 0.15mm max wear clearance between piston and cylinder mean? :confused:

dwtaylorpdx · « **Reply #4 on:** December 31, 2009, 12:37:21 AM »

They are drilled in place, however a good engine builder can bore them out and put sil-bronze ones in.

Dave

BlueBMW · « **Reply #5 on:** December 31, 2009, 06:51:39 AM »

From what I can tell those + numbers are tolerances meaning it could be up to that much larger than spec. I haven't done much engine building so I cant say for sure. Those are just what I could find in technical documentation.

wannam42 · « **Reply #6 on:** January 01, 2010, 11:03:56 PM »

No worries, BlueBMW.

Interestingly, this is more complete and quite similar to the tech info that cecotto gave in this thread: http://m42club.com/forums/showthread.php?t=1985

It looks like the E36 and E30 clearances are the same.

wannam42 · « **Reply #7 on:** January 01, 2010, 11:10:58 PM »

I almost forgot. Thanks for the info as well, Dave.

I'll be sure to ask the machine shop to do this. Not sure if this is really necessary though. What do you think?