I just registered for this board and I'm a kid in a candy shop! What a find. My first question: I have an '82 240D with a very tired engine, even though it has only 195K on it. Oil consumption is about a quart per 200 miles. I've only owned it for a couple years, so previous owners may not have followed good diesel maintenance practices. Anyway, locally, I have come across a rusty '81 300D, naturally aspirated, with an egine in excellent condition I can pick up for $400. Since both vehicles use the 123 chassis, I'm wondering if can I replace the 4 cylinder with the 5 cylinder relatively easily as an alternative to overhauling the 4 cylinder? Does anyone know of problems I'd encounter? Many thanks to responders.
Mike F.
82 240D, 82 300SD

I have done a number of diesel to diesel and petrol to diesel coversions over the years in a number of different makes of cars..some easy, some pure B*****ds!

As you have a complete donor car I would say it will be a fairly easy conversion. The doner car will have all the parts you need, I suspect, radiator and mounts, exhaust manifold + down pipe, remember the 5 cyl is basically the same as the 4 with an extra cylinder grafted on the front (that maybe is a bit simplistic!!)

seems a good way to get a cheap engine a supply of spares and more power

I'm new at the four cylinder end of this, but I've scattered a TON of W123 five cylinders. I'm crossbreeding a '78 and an '82 240d right now....and both the dead and live 240 motors happen to be resting on the shop floor next to an '81 five cylinder. Mounts are the same (measured/compared a parts car).....as the motors are installed in the cars, it's the most easily imagined as adding another cylinder to the REAR of the motor. Driveshaft and shift linkage rod(s) have got to be shorter on the five-cylinder car....radiator and oil cooler WILL bolt in....(done that) and the wiring will be the same except for the glow plug controller and wiring. Shouldn't be a bad job with both cars setting there....but you'll lay under both of them for a while.

Jim Steere
Everything Automotive
Crystal, MI