M50 Short Block

[93 525 Paul]

So I'm thinking I will freshen up the bottom end of the M50 shortblock I bought off Craigslist. On BMA and AutohausAZ I only see rod bolts and no main bolts.
Where to source mains?
Where to get instructions for torquing rods/mains?
Any reason to shy away from rod bearings? I read somewhere they were select fit and you can't just (like a domestic) buy a set of rods and mains and pop 'em in.
Input please (this is a daily driver, no special circumstances.)
Thanks in advance
Paul

[Dave M]

Did a very similar job to a used M50 block a few years ago. I believe I found the main and rod bearing at BMA, but I always call and they almost always find what I need. I'm sure they also sold me the rings and the front and rear main seals etc. I had the cylinders honed and installed the bearings etc. Everything is working great five years down the road....

for torques, I use

1AZ Main bearing screws
Replace, wash and oil main bearing screws

S38/S14/M40/M42/M43/M44/M50/M41/M51/S50/S50 US
M10
Torque 20 Nm
Torque angle 50 °
__________________________________________________ ____

1AZ Connecting rod bolts

Replace, wash and oil conrod boltsM20/M21/M40/M41/M42/M43/
M44/M50/M51/M52/S52/S50 US/
M70/S70/M73
Application torque 5 Nm
Torque 20 Nm
Torque angle 70 °

I have the complete BMW torque data document (1997). I f you pm me an email, I'll send it along.

Dave

[93 525 Paul]

Did a very similar job to a used M50 block a few years ago. Everything is working great five years down the road....

I have the complete BMW torque data document (1997). I f you pm me an email, I'll send it along.

Dave

It's great to hear that, thanks a ton for the doc, PM sent. I am a happy camper. I see 90% of what I need on AutoHausAZ but will give them a call to try and get it all.
The head is at the machine shop for a dip, all lapped and ready to reassemble. Tranny (4L30E) is on the bench now for a refresh. Glad I have a SS bench top, that fluid just gets everywhere.
Pure joy. I have the ASTG manual and a nice pdf an Aussie published on tranny reassembly tricks. Wish me luck.
Comments, tips, tricks welcome.

[93 525 Paul]

Did a very similar job to a used M50 block a few years ago. I believe I found the main and rod bearing at BMA, but I always call and they almost always find what I need. I'm sure they also sold me the rings and the front and rear main seals etc. I had the cylinders honed and installed the bearings etc. Everything is working great five years down the road...

Dave

When you did that did you use standard rod and main inserts? I see .25mm oversize, but am thinking standard. On rings did you go oversize and file to fit? I've always done F2F on my domestic engine builds. I see on Pelican Parts that the piston pin bushings are a "must replace" item. Did you?
So far thinking hone, rings, main and rod inserts, main bolts, rod bolts, timing chains, pump chain.
What am I leaving out?
Paul

[whiskychaser]

You might not need any of these but this was my shopping list when I did my chains:
TIMING CHAIN UPPER 11311432177

TIMING CHAIN LOWER 11311432176

CHAIN COVER GASKET -LOWER 11141720638

CHAIN COVER GASKET-LOWER 11141720639

CHAIN COVER GASKET-UPPER 11361740840

TENSIONER ARM 11311726503

TENSIONER SPRING 11411706809

TENSIONER BEARING BOLT 11111722324

TENSIONER BOLT CIRCLIP O7119932863

GUIDE RAIL - UPPER 11311722651

GUIDE RAIL - LOWER 11311726480

THERMOSTAT HOUSING GASKET 11531748O47

WATER PUMP 'O' RING 11511711484

[93 525 Paul]

Thanks for the tensioner info, hadn't even considered that.
What is the stock specification for piston to wall clearance? The current average is about .0037" which seems high. It might be OK for forged pistons, but I'm assuming the stock Mahle pistons are cast. Is that correct?
Dave M, did you check wall clearance in your refresh?
Thanks in advance.

[Dave M]

Thanks for the tensioner info, hadn't even considered that.
What is the stock specification for piston to wall clearance? The current average is about .0037" which seems high. It might be OK for forged pistons, but I'm assuming the stock Mahle pistons are cast. Is that correct?
Dave M, did you check wall clearance in your refresh?
Thanks in advance.

Hi Paul, sorry, I thought I replied to this a while ago. Maybe got distracted.......... Anyhow, I used standard 'everything', nothing oversized. It was a low mileage block and measured out fine (don't recall measurements) Didn't do the piston pin bushings. Didn't check wall clearance, but probably would if I was doing it over.

Dave

[93 525 Paul]

Hi Paul, sorry, I thought I replied to this a while ago. Maybe got distracted.......... Anyhow, I used standard 'everything', nothing oversized. It was a low mileage block and measured out fine (don't recall measurements) Didn't do the piston pin bushings. Didn't check wall clearance, but probably would if I was doing it over.

Dave

Thanks Dave. I hear the BMW blocks wear slowly and the ridge is not pronounced, so I doubt the cylinders are far out there. I just really wonder what the stock wall clearances are. My buddy says run it, but I just wonder.

[93 525 Paul]

Beemer tech told my brother that the max allowable cylinder wall clearance for a worn piston is 0.113mm (.0044") so about four and a half thousanths of an inch. Looks like my replacement block is right at the limit, so we will see how she does.
Stock cylinder wall clearances are .011mm to .043mm (.0004" - .0017") so the cylinders are a bit more worn than I would have thought. Not wonderful, but not a catastrophe.
didn't look like "max wear" cylinders to me.
Shows you what I know
gnarly before
http://i123.photobucket.com/albums/o284/pmcdougal/BeemerEnginePull002.jpg
pretty after
http://i123.photobucket.com/albums/o284/pmcdougal/HonedCylinders.jpg
any better?

[93 525 Paul]

AutohausAZ doesn't have main bearing bolts and responded to my follow up with "we can't get 'em." Any suggestions other than BMA, Rock Auto, Pelican???

[bubba966]

AutohausAZ doesn't have main bearing bolts and responded to my follow up with "we can't get 'em." Any suggestions other than BMA, Rock Auto, Pelican???

ARP - Main Stud Kits for BMW 3 series 318 325 328 m3 5 series 528 530 535 540 M5 6 series 635 m6 (http://store.vacmotorsports.com/arp---main-stud-kits-for-bmw-p115.aspx)

[93 525 Paul]

Hmmm, thanks for that but was thinking more plain jane stuff. If it were turbo or hi rev app you bet.
Anyone familiar with these guys?
BMW Parts - Discount BMW Parts - BMW Auto Parts - Online Catalog - Free Shipping - RM European Auto Parts (http://www.rmeuropean.com/bmw-parts.aspx#Category)
They show a stock replacement for about a hundo less than the ARPs.

[93 525 Paul]

Got the block washed and scrubbed down and brushed hard in and out, got quite a bit of grit out of it even though it had been baked at the machine shop. I painted it and trial fitted the crank in the new std bearings dry with Plastigage and all the mains show at about one and half thousandths of an inch clearance. Perfect in my book. Cleaned up all the Plastigage residue and assembly lubed the crank and re installed it with new bolts.
I've got to say the "clean room wipes" that Pelican Parts recommends are awesome. That's a great tip. Bought some on fleabay and am happy I did.

Now on to the ring installation, pistons, rod bearings et al.