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Old 05-25-2021, 01:43 PM   #1
Nick M3
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Welp. S50B32 Rebuild Time...

The yellow car started making a rather unpleasant noise that I really, really, really wanted to tell myself was related to the new clutch I put in. Alas, when I pulled the transmission, it was clearly not the issue.

Once I drained the oil, it was concerningly sparkly, which pushed me straight to "drop the engine out." (I considered pulling the pan in the car, but decided that it wasn't worth the double work.)

At this point, I've got the engine out, dropped into the basement shop, and have pulled the pan to diagnose.

It turns out that the #3 rod bearing spun. The good news is that the crank looks pretty clean. I'm hopeful that it can be saved. Yes, there's some marking in the journal, but no apparent gouging. It all looks like it can either be polished or cut, so as long as there isn't any hidden cracking or other damage, I think it can be reused.

The real question at this point is how extensive a rebuild I want to do on this motor, assuming that the crank can be saved? Given that I have to deal with a machine shop, my current thoughts are:

1) Repair crankshaft, if possible. (This is a go / no go gating question.)
2) Head rebuild. The scope of this is the biggest question for me. The motor has about 100k on it, so I guess we'll see what it looks like once I get the valves out.
3) Piston Re-Ring? This is pretty cheap, but is the thing that I've no experience with. With the head coming off and the crankshaft coming out, this seems like a no brainer, though. Plus, while it's apparently technically possible to pull a rod without pulling the piston, at a minimum, rod #3 needs to be checked.
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2011 M3
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Old 05-25-2021, 01:50 PM   #2
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Ugh, oh man. So sorry. Good luck!
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Old 05-25-2021, 02:40 PM   #3
John V
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I'm sure you have a machine shop that you like dealing with, but Chuck at Abacus Racing (in Va Beach) did a lot of the BMW motors back in the day for Bimmerworld (IIRC). I had him do the machine work on my M54 block and he also file-fit the rings for me. That engine had excellent leakdown until the day I sold it (and presumably beyond then). He also has the deck plates (maybe not needed for the iron block motors?).

Sorry to hear about this, but building engines is fun. If you need any measuring tools for bearing clearances and bore sizes, I have all of them.

Bear in mind if you re-ring, you really should check the bores for dimensions and ovaling, and at the very least give them a light ball hone.
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Old 05-25-2021, 02:55 PM   #4
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Quote:
Originally Posted by John V View Post
I'm sure you have a machine shop that you like dealing with, but Chuck at Abacus Racing (in Va Beach) did a lot of the BMW motors back in the day for Bimmerworld (IIRC). I had him do the machine work on my M54 block and he also file-fit the rings for me. That engine had excellent leakdown until the day I sold it (and presumably beyond then). He also has the deck plates (maybe not needed for the iron block motors?).

Sorry to hear about this, but building engines is fun. If you need any measuring tools for bearing clearances and bore sizes, I have all of them.
I've used Tyson Machine in the past, and other folks are using Rockville Ring and Bearing.

All things being equal, VA Beach is a bit of a pain in the ass for me, but who knows? I hear that Rockville R&B is totally overwhelmed. Neil Simon is unhappy with his last experience with Tyson. Apparently Burtonsville Machine is pretty much defunct. So... I dunno.

Of course, I need to also balance the cost of this vs. an(other) S54 swap. I like this motor a lot, but I can do an S54 for under $5k. Almost all of the supporting parts for an S54 swap are shared with the euro motor. And then I'd have another 1,000 rpms, 50hp, and wouldn't need to source parts from Europe.
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Old 05-25-2021, 03:33 PM   #5
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My vote is to keep the Euro motor because it's just cooler and I'm not really an S54 fan. But an S54 E36 is still super cool.

VA Beach is a bit of a pain but it's a fun place to visit, and they have great fish tacos. I would at the very least call them and talk to Chuck. I don't know that he's familiar with BMW engine codes but if you tell him what the motor is out of my guess is he'd understand what was up. If it were me, I'd at the very least mic the crank journal to check for distortion and check the bores for roundness. Not worth driving to Va Beach if what you have isn't buildable.
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Old 05-25-2021, 03:40 PM   #6
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Quote:
Originally Posted by John V View Post
My vote is to keep the Euro motor because it's just cooler and I'm not really an S54 fan. But an S54 E36 is still super cool.

VA Beach is a bit of a pain but it's a fun place to visit, and they have great fish tacos. I would at the very least call them and talk to Chuck. I don't know that he's familiar with BMW engine codes but if you tell him what the motor is out of my guess is he'd understand what was up. If it were me, I'd at the very least mic the crank journal to check for distortion and check the bores for roundness. Not worth driving to Va Beach if what you have isn't buildable.
Yeah. I want to keep it. I just also don't want to put a stupid amount of money in.
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Old 05-25-2021, 03:43 PM   #7
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Quote:
Originally Posted by Nick M3 View Post
Yeah. I want to keep it. I just also don't want to put a stupid amount of money in.
Well, your other option is to do what drag racers do. Polish the crank with some emery cloth, visually check it for cracks, mic it and assuming the dimensions are ok, throw a fresh bearing shell at it, measure that rod, and get back on the road.
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Old 05-25-2021, 03:50 PM   #8
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Quote:
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Well, your other option is to do what drag racers do. Polish the crank with some emery cloth, visually check it for cracks, mic it and assuming the dimensions are ok, throw a fresh bearing shell at it, measure that rod, and get back on the road.
I'd be lying if I claimed I hadn't thought about just doing that. But it seems a little bit too half assed for the effort.
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Old 05-25-2021, 04:12 PM   #9
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Any idea why it spun the bearing? Is that common in the S50?
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Old 05-25-2021, 04:14 PM   #10
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Any idea why it spun the bearing? Is that common in the S50?
It's a BMW M motor. They do that.

I fucked up by not changing them when I put the motor into this car.
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