Will an 82 motor fit into a 78 chasis without any major problems??

Yes, both are W123. I believe the automatics are the same as well.

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Actually, there's coupla issues involved - nothing major:

Acclerator linkage on yer '78 routes to passenger side along firewall. You will need the '78 manifolds, associated butterfly valve linkage and valve cover accel linkage mechanism. Treat the '82 donor engine as longblock, you'll be better off. And then using the '78 manifolds you'll see there's nowhere to hang the '82 oil vapor box that recycles blowby to sump. Need to drill and tap holes for bolts in the '78 manifold - or cap the hole in the sump.

You'll also need the bosch pencil plug update kit. Your '78 chassis is wired with relays for old style loop glow plugs. The '82 engine runs on pencil plugs.

why can't I use the 82 manifold? what do you mean by "longblock"??

Overall, this all sounds very doable, thanks for the info, much appriciated!!

Why??? Because '78 manifolds include passenger side accelerator linkage unique to the '78/79 chassis. None of the accel linkage is the same between '82 and '78..... EGR / 3-into-2 vacuum valve, all fiddly bits to the pedal are entirely different and not interchangable. You'll find tons of junk on the '82 engine that aint on the '78.

My advice is strip the '82 engine down to bare-bones longblock and use '78 components for easy bolt-in operation. Then scrounge up pencil plug kit to upgrade the '78 wiring harness and relays.

im a little tired, and just drank like half a bottle of nyquil but ill do my best to help. In 1981 they changed engine styles you have the 1981< style what they did was they routed the accelerator linkage to a butterfly flap on the intake to help create vaccume at idle and suck the EGR gasses into the intake. I just removed the butterfly plate (two flathead screws) swapped out for the old Non-egr exhaust manifold and removed the accelerator linkage. The catch-tank is easy to remedy, just cut the dump-tube off and either get it welded or kink it so oil doesnt flow out. (Really if you really need to use the catch-tank its time for an engine rebuild..) as long as you have the two engines to work with you should beable to swap engines and fix the minor bits and peices between one another. One thing i will suggest to do while the engine is out of the car, replace the waterpump with OEM brand one, and check the timing chain for stretch, do any other preventive mantinence while its out of the car, because its alot easier out of the car than when its inside.

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Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
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1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

The 82 engine has 82,332 origional miles on it. Would you still change out the pump? These engines don't come with an OEM pump??

Thanks very much for the info. As you can see I'm new to Mercedes. I hope this wasn't too painful for you. Thanks again

It does come with an oem pump, i would exchange it for the same quality brand. its just easier out of the car, dont worry it wasnt a hassle at all glad to have you here.

__________________
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac?

As long as they would add one additional commandment for you to keep thy religion to thyself.
George Carlin (Wonder where he is now..)

1981 240d (engine donor 1983 240d) recently rebuilt engine hurray! - No more.. fought a tree and the tree won.

pearl black 1983 240d 4speed (Converted!@$$%) atleast the tranny was rebuilt.

Well this is a little more of the same question. Can I swap a 1980 240 D motor into a 1982 240D sedan? Will I run into some of these samp problelms? The 80 had a standard and the 82 has an auto trans.
Thanks