320i m10 main bearings HELP

[euro02]

Hey guys, long time since ive been on here. ever since i moved to idaho i have not had any 02s or e21s. have been struggling with my mercedes addiction.

finally got back into the game, got a 82 320is, after driving it pretty hard one of the main bearings went bad. 

can someone help me out with what bearings to get? should i replace all four? i plan on keeping on driving it hard. its all stock except has weber 40 side drafts. 

so, should i replace all four? if so what size should i get? what brand is better? ive never did any work on the inside of the engine personally so bear with me plz

[Preyupy]

How do you know "A" MAIN bearing went bad?  That is fairly rare in a M10 engine unless there was a drastic loss of oil pressure then it usually takes out mains and rods.   All M10 engines use the same bearings (the M30 uses the same bearings, just more of them).  It would shock me if you have a damaged main bearing without also having at least 1-2 rod bearing damaged at the same time (oil goes FROM the main bearing TO the rod bearings)   

 

If you have the pan off and have inspected ALL of the bearings and the crankshaft is not damaged you need to figure out what size the journals are before you can order bearings.  You can only buy bearings in full sets (unless you are talking S14 rod bearings) So you have to buy them so I would replace them all.  

[euro02]

my inexperience is proven lol its actually a rod bearing that went bad. 

so from what ive been reading i measure using a caliper tool right?

[Mike Self]

I hope you're not gonna replace rod bearings without pulling the crankshaft out and taking it to a machine shop to be micced and ground to proper undersize (or at least polished if you're really lucky and didn't score the crank surface).  

 

Just clapping in new bearings (even if you check the size with a micrometer) is asking for trouble sooner rather than later....

 

A thought...since your E21 is an 82, it has the 1.8 liter engine; I'll bet you can find a good 2002 crank with rods for about the same money as having yours turned (presuming it's turn-able).  It should bolt right into the E21 block and get the engine back up to its full 2 liters...

 

mike

[Preyupy]

if you can't feel and groves in the rod journal AND there is no discoloration of the big end of the connecting rod you MIGHT get away with slipping a new set of bearings in it.  If you look at the back side of the bearings you take out you should see a STD, 0.25, 0.50 marking that will tell you if it is Standard, 1st or 2nd undersize.  You should also check it with a micrometer to make sure a set of calipers really aren't accurate enough. 

[Preyupy]

4 minutes ago, mike said:

A thought...since your E21 is an 82, it has the 1.8 liter engine; I'll bet you can find a good 2002 crank with rods for about the same money as having yours turned (presuming it's turn-able).  It should bolt right into the E21 block and get the engine back up to its full 2 liters...

The connecting rods are the same between the 1.8 and 2.0 liter.  The difference is the placement of the wrist pin in the piston.  If you put the 2 liter crank in with the pistons you have they will stick out the top of the block 4.5mm at TDC.

 

I also don't recommend just putting a set of bearings in it without a serious inspection (why did it knock a bearing in the 1st place?)  But you would not be the 1st nor the last to do it.  

[euro02]

i can faintly see STD marked on the bearing, i attached some pictures. the surface of the crank feels smooth without any grooves. i havent measured it yet.

 

now you guys got me thinking about a 2.0 lol

 

changing plans now, ill throw in a set of new bearings and drive it as is for now, in the meantime think about building a better engine.

 

if i wanted to build the engine up, should i start with a 2.0 or just bore the 1.8?

 

 

[jimk]

Looks like a spun bearing to me.  Rod caps on in the correct orientation?.  Crank needs polishing too.

[euro02]

2 hours ago, jimk said:

Looks like a spun bearing to me.  Rod caps on in the correct orientation?.  Crank needs polishing too.

 i dont know if theyre in the correct orientation, ill have to check tmr. im assuming it is since the bearings are original

[jimk]

Bearing picture appears to be of the outside of the bearing.  That area should not have any marks.  If it has, then it was spun.

[Deilke53]

Agree, that's for sure a spun bearing. Can you tell whether its tang was sheared off or pushed flat?   

 

I've always wondered how many spun bearings are the result of rebuilds where at least one rod was accidentally installed backwards.  Doubt they'd ever make that mistake at the factory, but I'll bet it happens fairly often in back yards.

[rcf925]

I wouldn't put that back together or you will be taking apart again real soon

[TobyB]

I grew up on a farm.  

 

If we'd seen that bearing in a tractor when the hay was down, we'd have gotten some

crocus cloth, polished the journal as well as we could, gotten out a set of .001" undersize shells and 

stock shells and mixed, matched and  plastigauged it until it was as close to spec as possible.

 

Then bolted 'er up and gone baling.    

 

And if we'd remembered and had the money and the creek don't rise, maybe gone back that winter

to see if it was OK, or if it was beating itself to death again.

 

 

But a tractor is massively overbuilt, like an M10.  Unlike an M10, it doesn't see high cornering loads,

nor do most have the weak #3 oil flow.  Nor did we beat on them most of the time, unless it was about to rain

or we got it stuck up to the hubs or something else along those lines.

 

 

But if you're going to thump on this, find a 2l donor engine (longer stroke, same bore, as Byron says above)

and build yourself something stout.  It won't be cheap.  You could also swap- the M20 fits nicely into the E21,

and is the engine the (heavier) car should have had in the US, anyways.  And wherever you can stick an M20,

an M5x will go, too, so might as well go right to the M54B30, for cheaper than an M20 with a good transmission(!!!)

or an S52/s54 for a lot more.

 

t

whose scope doesn't creep, it jumps in leaps and bounds

[Henning]

17 hours ago, euro02 said:

i can faintly see STD marked on the bearing, i attached some pictures. the surface of the crank feels smooth without any grooves. i havent measured it yet.

 

 

 

 

If that is the outside of your bearing, I'd like to see the inside of the rod cap. Expecting it to look quite similar, you should seriously think about a replacement engine- of what kind ever.

 

hen

 

[tech71]

You can do like Toby described but  as he infers, dont expect it to last long. I can feel the grooves in that journal catching on my fingernail from here. Grooves, galling, pitting, displaced metal, it's all there. If one looks like that wonder what the rest look like. Even cleaned up that suckers going to run hot. If you try to use it be sure to dig out the bearing metal packed into the oil passage.

  When you say "driving it hard" does that mean exceeding redline on RPM? A lot? for more than a second or two?The older an engine gets the less it can tolerate the abuse. Bearings will spin. They put a red line on the tach for a reason. Hows the oil pressure?

Get another engine cause that ones done.

Too bad you dont live closer to this guy, plug and play.

https://portland.craigslist.org/clc/pts/d/portland-bmw-m10-motors/7088461833.html

Edited April 1, 2020 by tech71