crankshaft bearing oversize

[DrA76]

the machine shop told me that i need new main bearing standard size , so i ordered   Main Bearings - M10  std size from Ireland Engeneering

received part # 5m1487-030  which is +30.

my Question is should i machine the crankshaft to +30 or should i order new ones? 
  

[kbmb02]

If your crank is standard and within spec, I would highly-suggest getting the correct bearings. (Grinding a crank to 0.030" would then mean nitriding it.) -KB

[Rich]

if you need new over sized bearings I have a set

[tech71]

Return them and get the correct size.

[Mike Self]

30 minutes ago, tech71 said:

Return them and get the correct size.

+1.  When I rebuilt my '73's engine at 204k, the crank showed less than .004" wear, so turning yours down just to fit the wrong bearings isn't a good idea.   If you (or the subsequent owner) ever has a problem with a spun bearing, you'll be out of luck as the crank will have been turned to the max and would either have to be welded and turned down, or made into a lamp for your man cave...

 

mike

[Son of Marty]

One more vote for returning them and getting the right size, for all the reasons stated above.

[DrA76]

IE was kind enough to refund.

And they don't have Std size in stock.

Looking for Std main bearing.

Or part # .

Thanks

 

[tech71]

Uh oh! This is not good, I need a set also and just searched most of the usual sources starting with Bluntech and Rogers tii then some of the Big Box BMW stores with little success.  Parts geeks, Rock Auto, not even Ebay! Did not check with Paul at Maximillian.

Found a set of possibles(BMW) on Pelican parts, normally I would rather poke myself in the eye than deal with Pelican but  I want to assemble soon so I went for it. Still have to wait 7 days.

 

https://www.pelicanparts.com/cgi-bin/ksearch/PEL_search_2016.cgi?command=DWsearch&description=11210666100-BOE 

 

Edited January 6, 2021 by tech71

[Henna318i]

I faced this same issue for my M10 engine project. All the vendors I contacted said the main bearing set are out of stock with no anticipated arrival date. I searched ebay and eventually found a Sealed Power set that is listed in the cross reference for M10 main bearings. Took a chance on them. When they arrived to my pleasant surprise they were marked KS with the BMW logo. There is still a Beck-Arnley Std set On ebay, but I have no idea who supplies them.

[tech71]

I have 2 sets on order with Pelican and they are getting them from BMWs main parts center on the east coast.

Could have gone thru BMW I guess

PN 11-21-0-666-100-BOE.

Keeping my fingers crossed.

[Son of Marty]

You might look into getting a set of m30 mains they seem to be in

stock, and just use the 4 of them. I haven't looked into it but I think they will fit.

Edited January 7, 2021 by Son of Marty

[Preyupy]

Mains and rod bearings are the same for all of the M10 and M30 engines (just more of them in the 6 cylinder engines) 

 

The Main bearings are also the same in the S38/M88 and S14 engines. 

 

The rod bearings however are different,  The dimensions of the rod bearings are the same but they moved the index tabs.  

[Henna318i]

The rod bearings are the same but I thought the mains are different. M10 main is 55 mm and I thought the M30 is 60mm.

[2002iii]

22 minutes ago, Henna318i said:

The rod bearings are the same but I thought the mains are different. M10 main is 55 mm and I thought the M30 is 60mm.

According to realoem.com you are correct. It makes sense if you think about the fact that the m30 has a heavier crank and puts more torque on it too.

Edited January 7, 2021 by 2002iii

[Preyupy]

I'm sorry you are correct the M30/S38/M88 mains are larger than the M10/S14.