I found a great running engine in a 1981 300CD (140K rest of car is ROUGH) to replace the blown engine in my 1981 300D. I just wanted to double check that there should be no differences in the 2 engines right? From what I have gathered there shouldn't be, but I just wanted to double check.

Assuming they are the original engines everything should be simular. The only exception I can think of was that the year the glow plug type was changed? Was it a mid year deal? The preffered glow plugs are the pencil type. I would have a quick gander to make sure. Check that replacement engine over very carefully. A compression test might even be a good ideal if possible. The indicated total milage on the doner car is probably way off. There are exceptions but do not count on it. A 123 mercedes with 140k will have an interior basically almost exactly like new in most cases. Again just my opinions. Best of luck.

If both engines are from the same MY, the only difference I can think of is the engine support arms, but that shouldn't matter as you can use the arms from the blown engine.

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83 300D 328k mi (623) Light Ivory - daily driver
82 300D 166k mi (881) Thisle Green - fixer upper
82 300D 282k mi (473) Champagne - parts

I was skeptical as well. He said it hadn't been started in 8 or 9 months (but the cobwebs in the engine bay said longer to me). I brought over my battery because his was dead, and it started on the first crank. Ran rough and smokey for the first 1-2 min then smoothed right out. I loosened the oil cap and it just sat there, no dancing around or anything. The rest of the car is rough from sitting in the NM sun, at least the last year with no rear window. Plus I can get the whole thing for $500, which gives me a good motor for my 300D plus an extra tranny and some other spare parts.

As long as you let the engine rise to operating temperature and the oil cap still stayed still you might do okay. Remember the coupes have coupe specific parts like the rear window regulators. You might sell enough off to get the engine free. My kind of preffered deal.
If the rear quarters are unrusted in that climate they too might sell well even on ebay. The shipping might be a bit but they are not available aftermarket I believe. Expensive as well from mercedes. Coupe doors with no rust might be a hot iitem as well.
The coupes are developing a following of sorts it seems with time.
Rough and smokey for a minute or so is normal in my experience with a diesel that has sat quite awhile. The second start will probably be cleaner. Sounds pretty good.

My thoughts exactly, plz don't send her to the crusher till shes picked clean.

too bad about the rear glass...

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Cheers,
Robert

Yeah, I plan to sell off the coupe specific parts. It even has the Euro headlights, unfortunately the drivers side is badly cracked. I didn't look really close, but I saw no rust, just BADLY oxidized paint and rough interior. Once I have it home I wil start posting parts on the board.