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Thread: M50 Short Block

  1. #1
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
    Posts
    264

    Default M50 Short Block

    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
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  2. #2
    Join Date
    Jan 2004
    Location
    Thunder Bay, Ontario
    Posts
    2,538

    Default

    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
    Last edited by Dave M; 01-31-2011 at 09:11 PM.

    10/90 Build 525im, 630,000+km, Eibach/Sachs, Engine Rebuild
    *RIP Oskar the DOG *

  3. #3
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
    Posts
    264

    Default

    Quote Originally Posted by Dave M View Post
    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.
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  4. #4
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
    Posts
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    Default

    Quote Originally Posted by Dave M View Post
    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
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  5. #5
    Join Date
    Feb 2006
    Location
    Oldham, England
    Posts
    3,078

    Default

    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
    Oct '00 E46 330i. Feb '92 525i (departed)

  6. #6
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
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    Default

    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.
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  7. #7
    Join Date
    Jan 2004
    Location
    Thunder Bay, Ontario
    Posts
    2,538

    Default

    Quote Originally Posted by 93 525 Paul View Post
    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

    10/90 Build 525im, 630,000+km, Eibach/Sachs, Engine Rebuild
    *RIP Oskar the DOG *

  8. #8
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
    Posts
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    Default

    Quote Originally Posted by Dave M View Post
    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.
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  9. #9
    Join Date
    May 2004
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    San Joaquin Valley CA
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    Default Stock Clearances, Max Clearance

    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

    pretty after

    any better?
    Last edited by 93 525 Paul; 03-31-2011 at 02:23 PM.
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


  10. #10
    Join Date
    May 2004
    Location
    San Joaquin Valley CA
    Posts
    264

    Default

    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???
    Link to my M50 engine rebuild thread
    http://www.bimmernut.com/forum/showthread.php/43339-M50-Eng-4L30E-Trans-RRR-Far-More-Than-I-Ever-Expected?highlight=93+525+paul


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