Difference between m20b25 vs m20b27 block casting

[hotballs]

I'm thinking about rebuilding an m20. I have a 2.7 eta bare block. Are there any differences to the m20 casting of the blocks? The diagrams are exactly the same on realoem for an eta and an m20b25.

I'm only talking about casting. I do notice there is a 2.7 embossed on the side. What else is different?

[scottinAZ]

I could be wrong, but IIRC the only block with any differences is the IX block. all others are the same. The 2.7 gets the extra .2 l from stroke, not bore size difference

[nando]

there may be differences but they are minor

more importantly, early blocks (including etas & B25s) use a different part number for the main bearings than later blocks.

[hotballs]

there may be differences but they are minor

more importantly, early blocks (including etas & B25s) use a different part number for the main bearings than later blocks.

Do the later main bearing shells have that little 'tab' in them? I noticed the main bearing caps and the shells both had that little tab on them so they nested themselves into place, is that the difference you speak of?

[nando]

they all have a tab in them, but the tabs are different so you can't put early bearings in a late block etc.

the early bearings have a 360* oil groove

[hotballs]

good to know. :up:

[Cinnabar325is]

Do the later main bearing shells have that little 'tab' in them? I noticed the main bearing caps and the shells both had that little tab on them so they nested themselves into place, is that the difference you speak of?

Just had this misadventure at the machine shop last week. :roll:

I ordered main bearings for an '89 (car is an '89) but the PO had swapped in a block from an '87. Machinist called up and wanted to know why the bearings didn't fit.

Specifically, the early style bearings have the single locking tab top and bottom. The later bearings have a single tab (top or bottom, don't recall) and a double tab on the opposite end. And there's the half-groove/full groove difference nando mentioned.

Having said that, does anyone need a set of brand new Glyco bearings of the later style? Can't return them now that the machinist opened the packaging.