Winterfjord, I've actually done this conversion. I had a 250C (with the M130 motor) with worn rings and a dodgy auto. I acquired a 250CE (with the M114 motor) with an excellent engine and trans but a very rusty body. How hard could it be therefore?

You have to swap everything. I mean EVERYTHING. Engine, wiring harness, fuel lines, exhaust (different manifolds) - everything. Even the accelerator linkage. You cant just install the injection wiring sub-harness and control unit - you need to swap the entire body harness - which means disconnecting from headlights back, stripping out from behind the dash (agony!!!) and even the rear harness all the way to the tail lights (for fuel pump wiring).

The M114 and M130 heads are not interchangeable so dont consider just swapping the top ends over. The M114 head will sit on the M130 block but oil and water gallerys do not line up fully and she aint ever going to run right. Fortunately I got this information from someone else who tried it so I went straight into engine swap mode. It took me about 3 months of my precious weekends to complete this "fun" little project and although the end result was a very tidy 250C"E" I wouldnt care to ever repeat the exercise. Not even under duress.

The M130 motor is a breeze to work on (the twin carbs aside) - with plenty of room to negotiate your way around the engine bay. The M114 on the other hand is a complete pig. MB managed to cram far too much gear for the D-jetronic setup on the right hand side of the engine. To say it is cramped does not begin to hint at the complete lack of space for getting any kind of tool near this sucker. IE two days of pain to remove the inlet manifold alone. And that was after several weekends of removing plumbing to actually reveal the inlet manifold. Many phrases incorporating "mongrel dog" were employed over the course of this excercise.

The M130 is a far better engine than the M114 - it pokes out more horsepower for a start and was far more widely available. In short I couldnt recommend this change to anyone but if someone else thinks they would like to have a go at it I'm more than happy to share the infinite details of whats involved.

If you really want more power and an injection set up I would definately find a 280SE or similar with the twin cam 2.8 (the M180 engine? - I forget but someone will correct me) with mechanical injection. There would probably be a similar amount of work involved to my project but the result would be far superior in terms of horsepower and K-jetronic simplicity. I really regretted not going that way with my car, especially as there are plenty of donors around.

Some other things to consider if I havnt disuaded you yet is that various D-jet parts are becoming scare as rocking horse poo - MAP sensors, control units (these are avail but at about $250) and fuel pumps. I know as I have two other cars with D-jet and I'm a little tired of hearing about how Bosch stopped making this that and the other thing "years ago".

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'71 350SL auto
'73 350SL manual
'98 528i (yeah I know but at least its German)

'71 250CE (sold)