Head stamped with 2,5 and 2,7??

[Benzon]

Hello. I need a New head for my m20 2,7 eta engine. My own head says 1705 885 and stamped with 2,5.
Ive found a head that Also has the same numbers "1705 885" but stamped with 2,5 and 2,7, how Come it shows both? Anyone can tell me why ?

[Speedtouch]

It's the standard 885 head casting - it was used on both 2.5- and 2.7-litre versions of the M20 engine.

I think only the later 885 heads had 2.5/2.7 stamped on them though.

[Benzon]

Soo.. the thing is, i need a New 2,5 head, because my own is broken. So This head with 2,5 and 2,7 stamped on it, is Exactly the same as mine with 2,5 stamped??

[Speedtouch]

Yes, it should fit just fine - AFAIK, all the 885 castings are all more or less identical.

However, if yours is a 'proper' eta engine (i.e., as fitted to the E28 525e or earlier 325e) beware, as the camshaft used fewer bearings compared to the 325i, since it was designed not to go much over 4,500rpm and used less bearings to reduce friction for economy.

Quote from the Zone Wiki:

" The older B27 engines used the "200" head, as found in the E21 320/323i and also the E12 520. In the Eta engine, this head was modified, using only four cam bearings rather than seven, very soft valve springs, short duration cam, and small inlet manifold ports. This gave the characteristics of very low revving, and very low fuel consumption, but also very little power. The 200 Eta head was mounted on a long stroke, straight six block. This made an ideal pairing with the head, and despite the lack of power and engine speed, the long stroke produced a great deal of torque across a very wide power band.

Later cars, from 1987 onwards, were fitted with a different cylinder head. This was based on the "885" head used in the 325i, and is known as the Super Eta. To accommodate the new head, the engine management was updated to Motronic 1.3, new pistons were made, the intake manifold was made larger to match the larger ports, the rev limit/fuel shut-off was increased to 5300RPM, and the exhaust was fed through twin pipes. The compression ratio was also dropped, owing to some detonation problems when using 95RON fuel."