installing older engine in newer car - PeachParts Mercedes-Benz Forum

shadetreemechan · #1 12-05-2021, 09:35 AM

I recently purchased an 83 240D with a window in its engine block. I pulled it and found that the #1 connecting rod had broken loose at the wrist pin and destroyed the block.
I have another 240 motor out of a 1978. We started it on the floor of the shop last week and it runs great, but i am hesitant to put it in to the newer car for a couple reasons.
1. The old motor has loop glow plugs. I am hoping I can simply replace them with the newer style pencil plugs and hook my existing factor fast glow relay to them. Are there issues with that idea?
2. I have read that there were horsepower upgrades that accompanied the addition of the egr and the head that accepts the smaller pencil glowplugs. This 240 body and interior are really nice, so I would hate to "depower" it with an older motor. They don't have many horsepower to spare.

I may be able to score a later model engine from a friend, but honestly the 1978 I have seems to be really low miles. It has almost no blowby and the camshaft lobes look like they just came off the assembly line.

I am not sure which route to go.

t walgamuth · #2 12-05-2021, 10:10 AM

There are many items which differ between the older and newer engines. In addition to the glows the mounting for the AC is different, the oil filter possibly and other things. I'd probably not do it.

I'd look for a good used engine.....a prospect that gets less likely each year.

...another possibility is to buy a crashed 300 of the later variety and switch everything over.

shadetreemechan · #3 12-05-2021, 11:20 AM

The spare engine I have is an early 123 so it has the same ac mounting and oil filter. I was just out looking at it more closely. It looks like the thermostat housing is slightly different to accommodate a vacuum sensor on the newer one. There is also a tach sensor above the flywheel on the newer one which must be for the cruise control. I wonder if there is a magnet in the flywheel of the older one. I have never had a 240 with cruise control and am looking forward to having that work.
The throttle linkage is very different because the newer one has an egr and an oil separator. The newer one has a drain port in the top of the upper oil pan to accommodate the oil separator so I can't swap intake manifolds to make it work.
I actually have an 84 grey market 240 to look at for reference, but it is way different from both the 83 and the 78 with yet a third type of intake manifold, and no remote oil cooler.
I just took the quick coupler apart on my compression tester and found the bad oring that was causing it not to work. I may do a compression test on the 78 engine this morning to give me more data.

shadetreemechan · #4 12-05-2021, 11:21 AM

I do have a spare 617 turbo engine, but from what I have read its not a drop in conversion for a 4 speed 240. Haven't you done it?

t walgamuth · #5 12-05-2021, 01:52 PM

I put a stick in a 300cd with turbo....an 82. In early 123 cars the ac is mounted high on the r side of the engine. Later cars from about 82 have it mounted low.

shadetreemechan · #6 12-05-2021, 11:07 PM

This motor I have with loop glow plugs and a 1978 casting number on the head has a delco r-4 mounted down low. It must have been the first year or some odd ball. I guess someone could also have swapped an older head on it, but it doesn't appear its ever been apart.
I hope I have found a solution. I picked up a 1982 motor today that was pulled from a pull a part by my neighbor in 2013. It is missing its injection pump, but turns over and doesn't look too worn from looking down the oil fill hole on the valve cover.
I will adjust the valves and do a compression test on it before making any decisions, but it is a carbon copy of what I pulled out of the car, so hopefully it is in decent shape.
It doesn't hurt anything to turn the motor without an ip on it does it?

Sugar Bear · #7 12-06-2021, 01:02 AM

I don't see how it could cause any problems. Rotate the engine a few turns by hand first, check that it has oil. IIRC that IP is pressure oiled, secure the hose before cranking.

Good luck!!!

t walgamuth · #8 12-06-2021, 07:21 AM

If the turbo motor is a known good motor I'd think hard about using it.

shadetreemechan · #9 12-06-2021, 08:15 AM

@sugar Bear: good call on the oil line to IP I had not thought of that.
@ t walgamuth, I thought the transmission had to be shifted back, driveshaft shortened etc to get a 617 where a 616 had been.
Maybe I need to do more research, though the turbo motor is from a wagon and has only 150K on it so I have kinda been saving it for the right wagon.
My wife dropped on me last night that christmas involves a 2600 mile road trip, so focus will turn to my 84 wagon right now to make sure its ready. I may not mess with this 240 again until after Christmas.

t walgamuth · #10 12-06-2021, 08:25 PM

yes the 300 engine requires a shorter front ds than the 240....cost maybe $200.

Sugar Bear · #11 12-06-2021, 09:38 PM

x2 on going from a 4cyl NA to a 5cyl turbo...w a 240D diff it will be nice.

t walgamuth · #12 12-07-2021, 09:51 AM

Well, when I did it I swapped all the different parts over. Keeping the 369 diff will give you the capability of peeling out but will sing a song on the highway and use 20% more fuel.

Skippy · #13 12-07-2021, 11:42 PM

Five cylinder into the 240D will require moving the transmission back by one cylinder's length, modifying the driveshaft by the same amount, and modifying the shift linkages. Diff swap to a 2.88 or 3.07 is optional, but I'd recommend it. I have a 300D with the manual from a 240D and it's worth the effort to have the turbo five cylinder with the manual transmission.

vwnate1 · #14 12-08-2021, 12:33 AM

I'm in to see how it all goes .

240D.Bill · #15 12-08-2021, 06:36 PM

On a similar note, I just pulled the timing gear, intermediate shaft(nut version), bushings, bearings, countershaft, and thrust from my '78, and dry fit all the corresponding parts from a late version '83. They look radically different but fit up just fine. Oil passages were added to the front bearing and shaft to improve lubrication. The inside and outside diameters of the relevant bearing/bushings were also adjusted for the larger diameter of the late shaft which used a bolt to fasten the timing gear as opposed to the nut from the early model. I'm confident it will work and reassured by the FSM which states for repair purposes the late version can be used if and only if the entire set is replaced(gear, shafts, and bushings, and fasteners). I am keeping the early diaphragm pump.