Hello guys,

I wanted to ask you which diesel engine will be ok for a w123 300D? I blowed my engine a couple of weeks ago and found out overhaulin is not an option due to block damage. I was thinking of buying a turbo diesel engine to get some extra ponies in the old guy and maybe a 5 speed tranny to add some extra top MPH.

Someone told me a good option would be a L6 turbo diesel from a newer mercedes (late 80's or early 90's) with its original 5-sd tranny. Can anyone give me some advice? Would it be too difficult to make a 6 cyl engine fit in a W123 body?

Thanx

itd be cool for a 6 cyl with 5 speed.. but i doubt it will fit the om617 looks like it barely fits in the engine compartment.. id stick another om617 in there.. and 5 speed.. thats a pipe dream

Thanks TheDon, I know the 5cyl engine looks tight, however the 6 cyl is almost the same length. Also I'm planning to use electric fans instead of the belt driven fan, so that would give me a pair of inches of clearance.

I wanted to use a OM603 engine, but I've heard this engine is available in 3.0 and 3.5 L. Is that true? Do they use the same base block?

the 3.5 is the rod bender...not all of them bend but can.. get measurements.. then go from there.. rember the engines can be pricey

The 603.96 (3.0) and 603.97 (3.5) use the same block casting so external physical dimensions are the same. If you check the archives, you'll realize that a 603.97 is probably not something you want to mess with. For that matter, 603.96 engines are neither plentiful nor cheap compared to 617s. If you want a 5-speed, it is more likely that you'll find a 5-speed that will mate up to a 617 than a 603 unless a 190D 5-speed fits behind a 603.

You will save yourself a lot of headache by selling your car as is or with a cheap running engine, then buying an 87 300D.

Sixto

Thanks for the advice guys, but I really don't want to sell my car. I has a very high sentimental value (used to be from my grandpa) and I've done some improvements to the car (ventilated disc rotors all around, 4-piston calipers in the front and moved the original front calipers to the back, nice exhaust, new body paint, new interior, hi-fi sound system, mercedes 16" rims, etc).

The engine died due to a damaged pushrod. The car has 250K miles on it

I would like to put a nice turbo engine on it. I already have an intercooler and a huge oil cooler to put with the new engine.

Is the power on the OM603.97 much more than the power on the OM603.96? Why is the .97 so unreliable?

Thanks

You have a very unique 300D engine if it has pushrods. AFAIK by the early 60s all MB passenger car Diesel engines went from flathead to OHC. I think you mean connecting rod

Check the archives for the monstrous levels of power those guys in Finland can extract from a Mercedes Diesel.

The trouble with the 3.5 stems either from weak connecting rods or a flawed design that allows chunks of soot to get into the combustion chamber. Over time the connecting rod deforms which causes the cylinder wear unevenly which increases oil consumption and reduces compression.

The 3.0 is not trouble free. If you overheat the engine there's a good chance the original head will develop irrepairable cracks. Redesigned heads are easily available.

From what I've read the 3.0 revs higher and makes power on top whereas the 3.5 is a torquer.

Sixto

You might think of doing this incrementally. Find a 617 turbo you can drop in immediately. Learn about turbodiesels as you max out that engine. In the meantime be on the lookout for a cheap 603 that you can build to your specs as time and budget allow. There will always be a market for a running 617 turbo so you should be able to get your money back when the hot rodded 603 is ready.

Sixto

Thanks for the advice Sixto. I think I'll follow it. What about the tranny? I would love to set the engine up with a 5-speed tranny. Was the OM603.96 Available with a 5-speed tranny? The 617?

Thanks

The 603 wasn't available in the US with MT. You might find a Euro 124 300D with 5-speed or as mentioned earlier the 5-speed out of a 190D might fit since the 601 and 602 blocks are very similar to the 603.

The 617 wasn't available in the US with MT either. There are Euro MTs in the US but most are 4-speeds. A 240D 4-speed will bolt up to a 617.

Sixto

i think you will find that the later six engines will have electronic elements unlike the older 617 motors. although it has been done, i dont think it is easy.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Thanks guys. I think I'll stick to the 617 engine. Can anyone tell me how hard it is to modify the 617 to get some extra ponies out of it?

It's a catch 22. It's easier to fit a factory stock 603 in a W123 than to get a 617 in a W123 to reliably perform as well as an 87 300D :/

Sixto

ummm, that's kind of bad. I wanted to put some more ponies in my old benz, but seems making a 617 perform better is difficult and the 603 has some electronic stuff that will make an engine swap kind of difficult.

Can anyone give some further advice? I'm kind of lost now, I really don't know what to do.

Thax

The 603.96 has minimal electronics that you'd want to keep. Basically there's flywheel rpm, AC compressor status and control rod sensor input to stabilize idle. It's a bit of wiring. You'll need the EDS controller from the host car. It's not more difficult than getting a 617 to perform like a 603.

Sixto