M50 Block/Head Compatibility

[Brew]

I searched.

Are all OBD 1 M50 Blocks the same?
Could a vanos block be bolted to a non-vanos head?
Are the pistons different? (I know that NV M50s have 10:1 compression and V M50s have 10.5:1)

Thanks.

[Wes325]

Yes, they all are the same and can be bored safely to 86mm.
Yes, a vanos head will work on a non vanos block. I.E.(stumc's engine)

[Bryson]

I was under the impression that only the non-vanos block could be bored out to s50 spec (not including the s50 of course) but they can be freely swapped

[Brew]

Thanks for the info guys.

Maybe we could make this into an FAQ if we got some more info on stroker motors and OBD1/OBD2 issues.

[Wes325]

I was under the impression that only the non-vanos block could be bored out to s50 spec (not including the s50 of course) but they can be freely swapped

I was talking about NON-vanos blocks only. Sorry for being somewhat vague with the answer.

[kylebes1]

Are the m50, m50tu, s50, m52, and s52 all the same block to begin with then bored out? and can all be bored to 86mm?

[Stu]

Are the m50, m50tu, s50, m52, and s52 all the same block to begin with then bored out? and can all be bored to 86mm?

There is a difference between the block castings for the 2.5's. The earlier motors ('91-'92) have a slightly larger, beefier block casting. For the first few years of production of the M50, BMW wanted the blocks to be conservative and not have issues with cylinder spacing. In '93, they began making the blocks smaller, just the right size for the 84mm bore of the 2.5 engines. With that said...

'93-'95 325i/525i (VANOS engines) can be safely bored to a little over 85mm, even 85.5. (requires forged pistons, as there are no M50 varient pistons with 85mm bore). You CAN bore these blocks to 86mm, but you'll be

'91-'92 non-VANOS blocks (325i/525i) can be bored safely to 86mm, and be stuffed with '95 M3 pistons (85.97 bore). My brother Alex and I both run '91 525i blocks bored to 86mm.

M3 blocks are different. 3.0L M3 blocks are 86mm bore stock (duh), and can be taken to about 86.3-4 (forged pistons). 3.2 blocks are larger yet, and have an 86.3mm bore stock, and can be stretched to about 86.5.

Don't know much about the 2.8's.

[kylebes1]

SO this would make piston spacing different for all the engines then, right? I guess the non vanos block works with the s50 since you have that, but is the VANOS m50 restricted to its own head?