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I've had the M20B25 engine sitting in my shed for about 3-4 weeks now and I've plucked up the courage to plunge my currently running and quite reliable but under powered 323i into a 325i engine transplant with no guaranteed successful outcome in the future.

The project car.


The donor car.


But with the resources available from this forum and a bit of advice I should be alright.

I had about half an hour last night so i got the car up on stands and started dismantling.


After about 4 hours work today between a friend and I the engine and box came out far far more easily than we had anticipated, given I cut up the 325i to remove the engine and it was still a right pain.


With my other e21 sold I have much more space for this project so here is where the old donk will sit.Note the lengths of timber next to my compressor used under the front wheels to get the hoist under the car.


Finally a shot of my e21 with its new engine in frame, but not in yet....


This is looking like something of a long term project with a bit of DIY fabrication thrown in for mounting the oil cooler, the O2 sensor, the extractors, the ecu, AFM and more as i work my way thru the project.

Hopefully the longer i take the more thorough i will be....but probably not....

looks like a good start there mate!

Cheers murran, I've got a day off work today so i might just get something else done!

In fact after calling a brake and clutch mob learned that i would need to measure the throw out bearing before they could supply me the kit, good excuse to go out to the shed and split the engine and box.


Clutch and flywheel off, its a 38 mm throw out bearing, not the other option....


I think I'll leave the flywheel as is, not much need to lighten it looking at that.


Socket with jack handle on breaker bar to undo flywheel bolts.


So......which part here is the selector shaft bush that needs replacing???


My heavy duty clutch kit will be ready by friday, the supplier only had them in regular duty so they are going to make a HD one up...woohoo!

Selector shaft bush shopping begins tomorrow!

You should put that 323i flywheel in! According to bmwfans.info, it is much lighther than m20b25's flywheel!

Nice to see swap pictures! I may do 320/6 -> 325i conversion in next summer myself.

edit: m20b25's 8.4kg versus m20b23's 6.3kg!

mmmm, good point on the flywheel. i fitted the 320/6 one as it was much much lighter!

murran wrote:mmmm, good point on the flywheel. i fitted the 320/6 one as it was much much lighter!

Yes, it weights same 6.3kg as m20b23 flywheel.

The 323i flywheel is the only one i have so its going in!

But should i get it machined for the new clutch?

I went back to the brake and clutch place today to drop off flywheel for machining, not much sense in springing for a heavy duty clutch if i doesn't bite into my mirror finish flywheel.

I test fitted my e21 headers to the M20B25, but that was about it.....

I will have to port match the headers a couple of mm per port as they are slightly smaller than the 885 heads ports.

You name the m20b23 underpowered, but the extra 20 hp wont get you much further!

Why not use a m50 instead?

Thijsse wrote:You name the m20b23 underpowered, but the extra 20 hp wont get you much further!

Why not use a m50 instead?

Because the M50 is crap M20b27 or one of the big 6es is the way to go IMHO,if u want a fair diffrence in performance

nothing wrong with a 3L m50, its heavier and a bit of a complicated install because the car is RHD though. That and the motors are expensive down here, probably triple the cost of them in the states. M52 2.8L are good too.

Clutch arrived today!



Also picked up my machined flywheel.

How much was the clutch? Did it come with a clutch aligner?

Good work mate. Am in a similar position myself. 320/6 on axle stands, 2.7 motronic awaiting clutch to go in. Then the wiring nightmare.

Keep the progrss pics coming.