My 300TD is showing signs of bad blow by and now it's getting harder to start. I think compression is dropping, and the engine might kick the bucket soon. It has 265k miles, and not the best history, but not bad either. I really don't want to rebuild it, so I'm considering an engine swap. Of course I could just dig up another TD engine (to keep the self-leveling suspension which kicks a55), or I can consider other engines. I would love it if a 124 engine would fit, like the 300E engine. Would it fit? I know a 280E (123) engine would fit, but i never see those around. I remember reading that ford engines fit easily, but I will never put anything american or japanese in there - only mercedes. Would a 116 engine fit (like 280se or something)? How about a 126 300SE engine? I want to keep it below 170 hp since I don't want to have to change out my differential, axles, bearings, etc. by having a more powerful engine, but like I said a 300E engine or any 3 liter gasser would rock. Basically I just want to know what of all the mercedes engines out there will fit easily (little or no fabrication or customization work) into a 123?

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

Any OM616, OM617na, and OM617t will work without much change.
Some 2.3L, 2.5L, and 2.8L gassers will work as well.
There have been a few lucky people to shoehorn a 5.6L V8 into the W123 (Not a drop in swap ).

The BIGGEST problem *you* have is your TD's rear hydraulic suspension. The 300TD's OM617 has a unique cylinder head to mount a timing chain driven pump. You can't just swap out the shocks or springs, you will never get it to ride right. There are Ultra-rare 240TD's, 230TE's and 280TE's out there, but you will be lucky to ever see two of those in person your whole life unless you own an MB repair shop. The massive bulk of Tx's out there are 300TD's.

Best bet is to get your engine rebuilt or find a good donor 300TD engine to swap out.

TE's and TD's arn't that hard to come by in Aus. You can find M110 (280) from coupes and sedans that have the hydraulic pump in the head.

Before you give up on your engine, you should do a compression and/or a cylinder leakdown test to know for sure the engine condition. It is possible that it only needs valve adjustment to run better again.

Also, these engines rebuild well and is much less trouble than an engine swap.

Best of luck,

I'll do the compression and leakdown tests next time I've got the hood open. I assume I use the glow plug holes to plug in the gauge?

It's not really that I'm giving up hope on the engine, it's more like since it's showing signs of crapping out, this is a perfect opportunity to do something I've always thought of doing. I love diesels, but I think I'd rather have a gasser in that wagon, despite the higher difficulty. I just get fed up with the lack of low end power with a turbo, and the lack of top end power with an NA. Couldn't I use an engine from a w124 300TE (which has hydraulic rear suspension)? Would it not fit?

I take it that the OM617 engines are the ones from the w123's... what's a OM616 from? I'm not that good with engine numbers but I know my way around the chassis numbers.

Being the purist that I am I'll probably just end up rebuilding the engine to keep it original, but it's fun to speculate... and if a swap actually happens I'd be excited too. Thanks guys,

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'82 300TD
'77 6.9
'75 280S
'74 280
'87 Porsche 944 turbo

OM617 are the 5 cyl 3.0L diesels and the OM616 is the 4 cly 2.4L diesel

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine