Help me understand what modded motor I (allegedly) have.

[Xaque]

Hey all!

I have the honor of being the current owner of a previously modded Touring and I'm trying to make sense of what's going on with the M20 under the hood.

The auction I won the car from described the motor as:

The inline-six engine is paired to a 5-speed manual transmission and uses 2.3L internals along with a 2.5L block and head.

And that's it.

From what I can figure, if accurate this was most likely done to make a stroker, as the stroke from the 2.3 is 1.6mm longer than the 2.5?

Engine stuff is relatively foreign to me, and the research I've been doing I can't seem to turn up anyone else doing this type mod as described. Any insight into what I might be dealing with would be greatly appreciated.

For reference, here's there car...



Thanks for any insight!

-Zack

[digger]

people have put the 2.3 crank into an otherwise stock 2.5L bottom end which has 76.8mm stroke (1.8mm more) to come up with a 2.6L

[Xaque]

people have put the 2.3 crank into an otherwise stock 2.5L bottom end which has 76.8mm stroke (1.8mm more) to come up with a 2.6L

Perfect and concise! Thanks!

(Not sure why I had just difficulty finding examples of this out there already.)

[digger]

Perfect and concise! Thanks!

(Not sure why I had just difficulty finding examples of this out there already.)

it is not very common since the 323i was sold in a limited market. alpina did this in 1985 with the C2 2.5 (the 2.5L was a different stroke to what bmw themselves produced with the m20b25) i think they then produced the 2.5 with the shorter stroke from b25 iirc maybe after bmw introduced the new crank for the m20b25

[Xaque]

it is not very common since the 323i was sold in a limited market. alpina did this in 1985 with the C2 2.5 (the 2.5L was a different stroke to what bmw themselves produced with the m20b25) i think they then produced the 2.5 with the shorter stroke from b25 iirc maybe after bmw introduced the new crank for the m20b25

It seems that the previous owner did this one up as a Hartge tribute (headers, wheels, cat delete)... With your post info, it would seem that they were going for a Hartge H26 (2.5) or H27 (2.7) build (based on the C2, as you said).

The definitely helps clarify things. So thank you very much!

This is helping me get closer to having an answer to "what's under the hood?" with something other than just "I have no clue." ;)