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Discussion Starter #1
I don't have any car yet, but am looking to go diesel in a Mercedes.
I'm looking at a wrecked 1979 W116 300SD turbo OM617 with 80K miles and swapping the motor into a 1985 W126 500SEL that has a bad motor. Both currently for sale.
Since I would have both complete cars would this be a fairly easy swap?
I am a very experienced mechanic. Only some with Mercedes.
I will probably need some detailed info if I buy them, just looking for the basics now. I realize there is likely a rear end ratio difference. Can they be swapped as well?
 

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'73 450SL, '83 300CD, '01 E320 4matic
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It ain't worth the expense!

You'd have to change literally everything. You'd really need a W126 donor car with a OM617 engine for all of the brackets, etc, that would be required. The entire fuel system is different, the transmission between the two cars is not the same, and the one currently bolted in the diesel car is not one that was used (in that configuration) in a W126. Once you get it bolted in, you'll need to have the correct length drive-shaft...

After all that, the electricals are all different, the suspension spring rate in the front is likely different (special compressor required for those springs) and you still have to get the instrument panel working...

So it'd be a lot less of a project to just get a diesel car.

It'd be less of a pain to find a 300D or something with no turbo and swap the turbo engine in.. still some work, but much LESS work, and more likely to give you good results without wasting a lot of money building a car that you can buy everyday in running condition for fairly cheap.
 

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Discussion Starter #3 (Edited)
WOW, thanks for the details akimball442. I'm basically a Mercedes noob and appreciate the info.
Another possible combo I could get is using the 79 OM617 turbo engine in a 81 W123 240D car. Does this sound more doable?
I have not been able to find any 300D's, and only a couple with a turbo in the last 9 months of looking that were less than twice the price of both of these cars. That's why I'm even considering it. I'm looking at having less than $1500 in the 2 cars. And after parting out the leftovers and scraping less than $1000 in the finished driver. I have the time but not the money to spend $2500- 3000+ on one of these cars. The only thing I've found for less are 240D's or 300D's with lots of problems.

To reiterate I will have 2 complete cars to work with. I knew the fuel system was going to need some changing. I wouldn't have thought the engine brackets would prevent a drop in of the older motor in the W126 . Would the engine/trans mounts need altering? Are the transmissions different lengths or just the driveshaft? I guess that means the V8 trans will not work on the diesel.
As far as electrical I didn't think the OM617 had much besides the glow plug controller and IP solenoids. Ignition wiring for those to work shouldn't be hard.
Instrument panel- wait to start light, water in fuel, fuel filter? As long as the speedo and fuel gauge work I''m good.
Lastly the 500SEL looks like the front end is as high as if the engine was removed even though it is only missing the intake on the way to removing heads, I think a heavier diesel engine would make it set a normal height without changing springs.
I could fabricate about anything I need for this swap as I have done for other 'unusual" vehicle /engine combinations.

A few more opinions and info will help me make up my mind.
 

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126: 1981 300SD, 1987 300SDL
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WOW, thanks for the details akimball442. I'm basically a Mercedes noob and appreciate the info.
Another possible combo I could get is using the 79 OM617 turbo engine in a 81 W123 240D car. Does this sound more doable?
I've actually heard of someone putting a 300sd engine into a 240D and peeling rubber because it's a lighter chassis. I don't know the details and cost but I suppose anything can be done.

I also have a friend who bought an early 123 300D which appears to have the 5 cylinder diesel engine with manual transmission. I don't know many more details about that. A dream machine would be a 126 SEC with a diesel engine, but it sounds like a total change and expense.
 

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1985 300SD 1988 560SEC 822 1976 450SEL 1981 300SD
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A dream machine would be a 126 SEC with a diesel engine, but it sounds like a total change and expense.[/QUOTE]


It's been done here.....we're on the same page here buddy!
 

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1985 300SD with a bad transmission and a 1985 300SD with a good transmission
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I've read of people pulling the manual trans from the 240d and sticking that in a 300SD so no reason the om617 to 240d should be "that" hard lol.

OP:
What are the two guys asking for the blown cars? If you're handy you might be able to buy them and then part them out making enough to buy a decent diesel outright. I know that engine would probably get you a good penny on some of the 4x4 boards. Apparently there's an emerging market for om617 offroading. I found that out when I was debating selling my 300SD with what I thought was an expensive fuel issue...turns out it was just a filter lol.
 

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126: 1981 300SD, 1987 300SDL
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I found that out when I was debating selling my 300SD with what I thought was an expensive fuel issue...turns out it was just a filter lol.
And I thought you were eaten by the zombies! Glad to see you found the problem and kept the survivor-mobile project up and running.

Maybe you can totally modify it and strip it down to basics for some hot-rod speed, or extra survival supplies. Maybe an extra tank if you haven't already.
 

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1985 300SD with a bad transmission and a 1985 300SD with a good transmission
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And I thought you were eaten by the zombies! Glad to see you found the problem and kept the survivor-mobile project up and running.

Maybe you can totally modify it and strip it down to basics for some hot-rod speed, or extra survival supplies. Maybe an extra tank if you haven't already.
I had thought about it, in fact that was the original plan. The more I look at the car and the more I drive it...I'm thinking that if I were to double my original investment (not including incidentals like tires, battery, fluids, pads) I'll have a REALLY nice car. Albeit one without upgraded A/C, but if I can get the old A/C running I'll charge it with propane lol.

I'm going to get some good pictures and open a photobucket for it, my buddy is really into car detailing and he went to town on the hood. There's now an 18"x18" square that is mirror shiny and glass smooth. I'm off Monday-Wednesday so that's my project since the parts I ordered (pads/valve cover gasket) won't be in until the middle of next week.
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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ZH,
Glad you decided to keep the car, they do kinda grow on you. Surprising how the dullest car comes to life with a bit of elbow grease.
Good luck and we all await pictures. I hope you do before and after shots. Those are always rewarding in the ensuing years.
 

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126: 1981 300SD, 1987 300SDL
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Yeah, it was designed originally as a luxury car so it kind of begs that direction. The W123 on the other hand... I've heard of it used in rallies, diesel station wagon drifting, etc.
 
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