Older m30 - rebuild questions

[Lurker27]

I've got a bead on a 91 e34, with 5 speed. The head has been rebuilt is the last 50k miles, and the guy says it burns no oil (I haven't driven it yet to evaluate power) and has recent compression/leakdown tests, ostensibly with good results. The rest has nearly 300k on it.

For a rebuild on this one, I'd want to do rear main seal, bearings on the bottom end, and maybe rings (not sure if rings are needed if compression/leakdown is good). I'm not sure exactly what pieces are needed - I have the manuals but haven't leafed through them yet. I'll eventually be going turbo.

Any input is appreciated.

[E30SPDFRK]

If the compression is good and you don't hear any knocking, it should be fine. If you still want to rebuild it just for piece of mind, I would do at a minimum rings, bearings and honing. The rest is up to you how involved you want to get.

[euroshark]

If you want to do the bottom end I would go ahead and do:

Front and rear main seals
Main bearings
Rod bearings
Thrust washer
Rings
Oil pump chain
Timing chain (especially because of the mileage - they stretch over time)
Gaskets of course

The cool thing about M30s is that as long as there is no damage to the crank you can usually throw standard size bearings in and put it together. Since the cranks are forged they should only be polished if anything, not machined (this is per BMWs recommendation). The main timing chains don't generally break even with super high mileage, but they do stretch over time and this will cause the cam timing to retard causing it to feel low on power. For rings you might be able to get away with just using a flex or ball hone and roughing up the bores a bit before you install new ones. The iron BMW used in M10 and M30 blocks is seriously some of the hardest iron EVER. Machine shops who know better will charge extra for boring these blocks because they tear up tools, so chances are there will be little to no wear in the cylinders. You might even see the original machining marks! My 225,000 mile block that I opened up recently had cross hatching in all 6 cylinders... They are super tough.

[JoeMadoo]

I always learn somethin from euroshark, haha

[euroshark]

That's what I am hoping for, I don't own an E30 so the only place on this forum that I am useful is here in the M30 section!

[Doughnut]

I always learn somethin from euroshark, haha

+1, he knows his shit!

And euroshark, my m30b35 was the same, near 250 000km on the clock when pulled from the donor car and still had its cross hatching on the cylinder walls.

[Lurker27]

Very encouraging - I knew they were bulletproof! I'll check out the compression test and do bearings/seals for sure. Thanks guys.

[Chells_88ix]

Euroshark, I am hoping you are correct. My e30 is sitting with the head off right now waiting for another to go back on, one of the rocker arms shattered. After picking out all of the pieces we went ahead and pulled the head to see if any had gotten into the cylinders and they all look pretty good to me, I couldn't feel any cuts or distinct wear in them. But when we did a compression test the cylinders were a bit lower than normal, what effect would the rocker being broke have on that test, any? I believe the valve was stuck in a partially open position. After reading this thread should I delay the reinstall and do the things you have recommended to this person. Glad you asked this question :). Thanks, michelle

[RickSloan]

Euroshark, I am hoping you are correct. My e30 is sitting with the head off right now waiting for another to go back on, one of the rocker arms shattered. After picking out all of the pieces we went ahead and pulled the head to see if any had gotten into the cylinders and they all look pretty good to me, I couldn't feel any cuts or distinct wear in them. But when we did a compression test the cylinders were a bit lower than normal, what effect would the rocker being broke have on that test, any? I believe the valve was stuck in a partially open position. After reading this thread should I delay the reinstall and do the things you have recommended to this person. Glad you asked this question :). Thanks, michelle

are you working on an M30 powered e30?

and +1 to always learning something from euroshark!

[Lurker27]

If you want to do the bottom end I would go ahead and do:

Front and rear main seals
Main bearings
Rod bearings
Thrust washer
Rings
Oil pump chain
Timing chain (especially because of the mileage - they stretch over time)
Gaskets of course

The cool thing about M30s is that as long as there is no damage to the crank you can usually throw standard size bearings in and put it together. Since the cranks are forged they should only be polished if anything, not machined (this is per BMWs recommendation). The main timing chains don't generally break even with super high mileage, but they do stretch over time and this will cause the cam timing to retard causing it to feel low on power. For rings you might be able to get away with just using a flex or ball hone and roughing up the bores a bit before you install new ones. The iron BMW used in M10 and M30 blocks is seriously some of the hardest iron EVER. Machine shops who know better will charge extra for boring these blocks because they tear up tools, so chances are there will be little to no wear in the cylinders. You might even see the original machining marks! My 225,000 mile block that I opened up recently had cross hatching in all 6 cylinders... They are super tough.

I went ahead and got the engine - is there a good resource for a diagram of these pieces, or will it be all done 'by feel'? :)

Also, do you have a recommendation for the best place to pick up these parts used.

Compression over 150 on all cylinders!

[pegase747]

Hi Lurker, you can find the engine parts diagram by clicking the following link :

http://bmwfans.info/original/E34/Lim/535i-M30/USA/L/M/1991/06/mg-11/

Hope that helps / Pierre

[Lurker27]

Great link, thanks! If I do rings, I don't NEED to hone do I?

[Lurker27]

This is going to be my build thread.

I was wrong on the compression:

175
170
175
175
175
175

Engine, now that it's been driven a bit, is strong as hell. Going to give it a seafoam treatment before the swap.

I ordered 335.de style mounts, and will have the engine in position 3. I will be using an 87 es manual driveshift. Wiring from the 1991 e34 seems pretty straightforward, and I'llneed to splice in the reverse signal.

I have a 533i flywheel on the way, and am getting a stage 3 e28 clutch kit to go with it.

EDIT: http://cgi.ebay.com/ebaymotors/F1-RA...Q5fAccessories

That fits, right? like this: http://forums.bimmerforums.com/forum....php?t=1038894

Just need to track down my e30 manual parts, now. It's AMAZING how much info there is on this swap. It can be done right for cheap :)

[Lurker27]

Got all my parts in, engine coming out of the 5 series. A quick question for those in the know - what do you think about seafoaming the engine while it is out of the car? I'm concerned about losing compression. I suppose I could just do rings too and be done with it - the PO noted the cross hatching when the head was replaced without my mentioning that euroshark tidbit. ;)

[Doughnut]

Got all my parts in, engine coming out of the 5 series. A quick question for those in the know - what do you think about seafoaming the engine while it is out of the car? I'm concerned about losing compression. I suppose I could just do rings too and be done with it - the PO noted the cross hatching when the head was replaced without my mentioning that euroshark tidbit. ;)

How do you know it's the rings and not the valve seats/ valve guides leaking?

Put the motor in the car and worry about that stuff later, You won't "lose compression."