M20 Main Bearing Differences and Compatibility

[SkiFree]

---M20 – Early vs. Late main bearings. --------------------------------------



*Early = ‘e’ blocks/ SINGLE TANG
*Late = ‘I’ blocks/ DOUBLE TANG


Here’s a picture of the difference between the 2 style main bearings



(note that these particular bearings have been coated).



You can see the ‘e’ main bearings (LEFT) have single “tangs” at either end that line up with the block and saddle. The ‘I’ main bearing (right) has a saddle ½ shell that is smooth (no oil journal) and has a double “tang”, but the top ½ shell is the same as the “early” style.

------Combinations and why it may matter.---------------------------------------


Why might it matter?
It does come down to availability (NOT performance). BMW used both Kobenshmidt and Glyco as OEM suppliers, which are carried by your preferred vendor (Ireland Engineering, Guten Parts, Blunt, Korman, Metric Mech., AZ Autohaus, etc.) or shop doing the work (TCMotorsports, Castro, Midnight Oil, Heritage Motorsports, Midnight Motorsports, E30 Motorwerks, etc.).

THE SET THAT IS NO LONGER AVAILABLE (NLA) IS THE ‘EARLY STYLE “e”’ .25-UNDER & .50-UNDER BEARINGs. All other bearing sets are still available at this time (7/19/12).

----Compatibility/Solutions?------------------------------------------------------


Contrary to what WORLDPAC states, you CANNOT simply retrofit a late bearing set into an early block (this has been the source of a fair amount of recent misinformation). See the picture below, the tang’s width is different and you would need to cut another tang slot in each of the bearing saddles to accommodate the second tang, the risk is too high to consider.



The BEST solution for the individual seeking NLA undersize single-tang bearings for their M20 ‘e’ block, is to purchase 2 sets of late “I” bearings and simply pair up the halves that have the oiling-groove in them. See picture.




Which M20 Compatible crank you have (b27,b25,m50/2,s50/2) has nothing to do with what style main bearing you need (other than sizing obviously).

If anything is unclear, feel free to ask. Hopefully someone can sticky (or put in DIY Section) this to avoid later confusion.

- Andrew @ Ireland Engineering

[MR 325]

Andrew, this is awesome. Thanks for posting!

[bmwstudent]

Yes thanks, jlevie gave me what i needed to know yesterday but this is definitely great info. Thanks,Skifree

[88SuperETABD]

Does IE have the early coated bearings in stock?? I need a set for my build, we've talked about it. You say theyre NLA. Am I Screwed?

[jlevie]

THE SET THAT IS NO LONGER AVAILABLE (NLA) IS THE ‘EARLY STYLE “e”’ .25-UNDER & .50-UNDER BEARINGs. All other bearing sets are still available at this time (7/19/12).

While it may have changed in the last few months, the bearings for all colors for nominal journal dimensions were available a few months ago. I'd hesitate to re-grind a crank as it is too easy to get a used one that only needs polishing, so I don't know about the availability of the undersize bearings.

If you want coated bearings, you first need to measure the journal dimensions. Next talk to who will be coating the bearings to see what the coating thickness will be. Then pick the color that will result in the correct clearance.

[Chruby99]

So to run a 360 groove on a late block we need to get 2 sets of late bearings and run the grooved bearing on the block and cap

[SkiFree]

Does IE have the early coated bearings in stock?? I need a set for my build, we've talked about it. You say theyre NLA. Am I Screwed?

Sorry if it was unclear, undersized (.25 and .50mm) early bearings are NLA. Replacement sets can be pieced together by using using 2 similarly sized late sets.

Standard size early bearings are still readily available. I've got 5 coated std. size early sets on the shelf.

As for under-sizing the crank. I'm with Jim. Any M20 cast crank that is ground undersized (not just polished) needs to be nitrated (will have a blue hue).

[SkiFree]

So to run a 360 groove on a late block we need to get 2 sets of late bearings and run the grooved bearing on the block and cap

In my mind that would be going backwards. There would be no noticeable gain in doing so.

Early style - 360' oil groove with single tangs
Late style - 180' (top half) with oil groove and smooth bottom with dual tangs.

To go from a late to early bearing configuration you'd need the block main-caps from the early block and they tend to be matched to the block from the factory.

[TobyB]

you'd need the block main-caps from the early block and they tend to be matched to the block from the factory.

Yeah, you can't swap caps on a block. It just doesn't work. Without some significant machining.

Tang.

t

[digger]

any quality differences or preferences between OEM, KS or Glyco main bearings? what do you get if you go OEM?i guess same question with rod bearings?

obviously OEM are more $$$ so neglecting that whats the deal? for a stock engine i wouldn't care but for a performance build which is better?

not looking for fancy coated bearings, may consider ACL for the rods if i can find a set but i hear they closed down.

current engine uses KS for mains and rods, no known issues

[SkiFree]

... no difference in quality of the bearings themselves. Some reason I gravitate towards KS's, merely for the fact that they seem to be consistently packaged more snugly.

[digger]

for some reason im leaning towards KS, dont know why maybe because Kolbenschmidt sounds more german

[jeffnhiscars]

for some reason im leaning towards KS, dont know why maybe because Kolbenschmidt sounds more german

Lol...that's how I make lots of buying decisions

[itsonlygeorge]

Sticky!


Sent from my iPhone using Tapatalk