Different M20 Engines

[andy325i]

Hi guys, does anyone know if the M20 blocks used in the E30 and the E34 are different in terms of where the alloy mounts actually bolt onto the block itself?

I.e would an E30 M20 fit an E34 and visa-virsa.

Any help much appreciated

[E34-520iSE]

AFAIK the alloy mounts are different, and the sump is different, but the blocks are the same. I understand there are only two M20 blocks, 80mm cylinders and 84mm cylinders, and are the same externally. The 84mm block has two small steam holes between the cylinder tops. Any one able to confirm this?

Cheers,

Shaun

[Rigmaster]

I asked this same question not too long ago- but got no firm answer.

The ETK shows 2 different part numbers for the E34 + E30 2.5i longblock engine- so there MUST be some significant difference(S). I am assuming it's something like the mounting holes in the block for the motor mount arms, but I don't know for sure.

I find it hard to believe that BMW would make these engines with any major differences- if anyone knows, please post it up!!!

Bret.

[bjl4776]

Like said already, the reason the part numpers are different is because the mounts and the oil pan are different. As long as the engine you have is a 2.5l than they are the same. You can just swap the pan and the mounts and they are direct replacements. Its the same way between the M50 in the E34 and the E36

[Jon K]

AFAIK the alloy mounts are different, and the sump is different, but the blocks are the same. I understand there are only two M20 blocks, 80mm cylinders and 84mm cylinders, and are the same externally. The 84mm block has two small steam holes between the cylinder tops. Any one able to confirm this?

Cheers,

Shaun

The difference in the blocks is that the 80mm block is from a 325/325i/325is/325ic while the 84mm block is from the 325e/325es. 2.5L block vs. eta 2.7L block.

[winfred]

the difference between the 2.5 I and 2.7 E is in the stroke not the bore, 5mm longer stroke on the E motor. i am going to build a motor for my 325is with a forged crank from a 524td which has the same stroke as a E and combine that with a slight overbore it will come out to around 2.9

The difference in the blocks is that the 80mm block is from a 325/325i/325is/325ic while the 84mm block is from the 325e/325es. 2.5L block vs. eta 2.7L block.

[winfred]

the only real difference between a e30 325i motor and a 89-90 525 motor is the 525 doesn't have the oil cooler adaptor screwed into the block (like a E motor, it can be added if wanted in a few minutes) and the dipstick is mounted in the oil pan on the 525 and in the block on the 325 but the size and shape is the same between both pans so a 325 motor will drop right into a 525 with the 325 pan, i plug the dipstick hole in 525 pans with a freaze plug and sell them for 325s as the 325 uses it's pan for a curb feeler. wireing and brackets are different but easyly swapped from motor to motor

[Rigmaster]

Does a BMW factory longblock come with the aluminum mounting arms + the oil pan included?? I did not think so, but I've never bought one......

As I said before, I cannot imagine that the difference(s) between the M20 blocks are very significant- it would just not make any sense to make them different for no apparent reason.


Bret.

Like said already, the reason the part numpers are different is because the mounts and the oil pan are different. As long as the engine you have is a 2.5l than they are the same. You can just swap the pan and the mounts and they are direct replacements. Its the same way between the M50 in the E34 and the E36

[ukm5]

they are different, the oil pan on the 525 has the dip stick mounted in it, where as on some others the dipstick goes into the block..

[E34-520iSE]

I have here a pic of my block after it was painted and I think I can see an aperture when the dipstick would fit in the block of a 3 series. If I knew how to post pics here I would show you what I mean. This would mean the difference between an E30 and E34 engine would be one small blanking plug in the M20 block.

Cheers,

Shaun