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M10 Disaster~!


LeeJohn

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Ok so ive been rebuilding a 74 megasquirt engine. I got the block tested and machined and all pistons and crank machined and ready.. upon assembly we realized the bearings werent right so we remachined them.. then once everything was put together we couldnt rotate the engine..

Problem was ENGINE SAG!!!!!!!! WTF!!!!! u guys ever heard of a m10 needing a bore alignment?

If i bore align it then i have to remachine oil pump timing chain and somehow a way to fit new seals..

If anyone out there has a good m10 block im in desperate need.. I just wasted god knows how much $ and time..

thanks guys

lee

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What do you mean the bearings were not right? What did you machine, the bearing shells?

If the main bearings are not in line, the top of the block is probably not straight either.

No amount of skill or education will ever replace dumb luck
1971 2002 (much modified rocket),  1987 635CSI (beauty),  

2000 323i,  1996 Silverado Pickup (very useful)

Too many cars.

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u guys ever heard of a m10 needing a bore alignment?

I've asked 'old-timers' and machine shops about this issue, most who've worked with the M10 says it's rare they need line boring. If anything, it's wise to make sure the crank is straight (they do bend).

Not sure where you're located, but I have a couple of blocks here in Southern California. -KB

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you can fix this with a line hone in about 30 minutes if you can find a shop with a line hone.

You can check to see if it's your block vs your crank by taking a machinists ruler and laying on the journals and then getting out a feeler gauge.

I'd bet real money you've got a cap on backwards or misplaced before I'd say that your block moved. Unless previously it had a bearing failure and got a cap hot.

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I don't know if you remember all my new engine drama but if engine sag was possible it would have happened to me. I think it has something to do with re-machining bearings???? Did not know you ever machined bearings in th efirst place. You have to dress the shoulders some but never hear of machining them. After you are done panicing I would take everything apart and see whats up

I'm not as dumb as I look

74 Verona

06 Audi A3

09 Mercedes C300

06 VW Passat

03 VW Conv Beetle

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After measuring checking and praying the middle of the block where the bearings sit is 7000th of an inch to high. I would have to recut causing the crank to sit higher. That would mess with oil pump and timing chain not to mention the seals. . The crank was balanced and is straight to my knowledge. Tomorrow I'll know more.

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We still don’t know what you already machined. I agree with oldguy and think you mixed up some bearing caps or put them on backwards.

Mount the caps on the block without the bearing shells and run a finger over the parting line. You should not be able to feel any step. I can't believe that your mains are 7/1000ths out of line. I have rebuilt hundreds of engines and have never seen that before.

No amount of skill or education will ever replace dumb luck
1971 2002 (much modified rocket),  1987 635CSI (beauty),  

2000 323i,  1996 Silverado Pickup (very useful)

Too many cars.

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If you have a main seven thou out of line, you have a broken block.

BMW didn't allow a thou, and I've never had one, used or blown up,

that measured anything more.

Like everyone else, I think something else is going on here.

And I wouldn't rule out PO actions.

If it had been mine, I'd have grabbed a different block already-

the blocks are one of the longest- lived and therefore most plentiful

parts of the 4- cylinder BMW line...

t

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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Im in venice CA.

tomorrow ill get exact specifics on what has been measure and analyized..

To my knowledge here the steps.

have a block. tested by xray and leak test.. = fine

make sure cyclnder walls are in spec 1mm bore = fine

extent of testing

preassemble notice play in front of engine (crank).. (only slightly off )

re machine block

preassemble engine now wont turn

notice bore isnt straight..

everything has been triple checked.. crank, rods, bearings etc......

sorry if ive been vague.. been on the road with only short handed responses..

thank you everyone for the responses.. When rebuilding a engine to the highest quality there are no shortcuts.. Ive learned alot and maybe thats the price ur paying for.. I just want to document something that potentially

can help people in similiar situations.. I mean for christ sake they r not building blocks anymore so time will tell future problems....

thank u all..

lee

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I have a block in Fullerton. It's got everything but the timing covers attached. I want to keep the head, so the whole shebang needs some dismantling. I also believe the bottom end to be worn out, but I've got it. Let me know...

Brendan

1972 BMW 2002 Colorado #2577807<p>

2015 BMW M5 Competition 6-speed

2003 Audi TT Coupe 225

 

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Guest Anonymous

Remember KISS. Keep it simple stupid. I pulled my main caps and found they were marked 1,2,3 ,7. Thinking a minute, oh yea the #7 must be the most rear main cap from a small 6 (very old original block with dubious pedigree). It took me some time to get all the caps back in the right locations. First crank wouldn't turn if they were not installed in proper location. Next I found that each one had to have the proper front back orientation. I can't remember how many combination I tried to get it with each cap where it was supposed to be and front to back right.

My mom used to walk me down to the bus and give me a KISS before I got on the "Little Bus". I know now it was to remind me to "Keep It Simple Stupid".

The same block you are using has been used on turbo race cars putting out 1500 HP no sag mentioned nor block distortion or the thing would have exploded.

have fun

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Guest Anonymous
I don't know if you remember all my new engine drama but if engine sag was possible it would have happened to me. I think it has something to do with re-machining bearings???? Did not know you ever machined bearings in th efirst place. You have to dress the shoulders some but never hear of machining them.

After you are done panicing I would take everything apart and see whats up

Insightful. Great tip.

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