OM617 vs. OM603

[Casey]

Hey everyone, just having some fun while bored...

Just wanted to hear some opinions on the differences between these engines.  I had a 6-cylinder OM603 in my W124, and it sometimes feels like a step backwards having the 5-cylinder OM617 now.  Don't get me wrong, I think it's a great engine and the turbo (which I didn't have on the OM603) makes it a higher-performance engine even in a 1000lb heavier chassis.  That said, I hear a lot of good about the OM603 too, and perhaps with a turbo it would be even more performing than the OM617 due to the extra cylinder.  But then again the displacement is about the same, so what's the comparison point?  It's kinda a shame Mercedes never made any bigger diesels than 3.0L except the problematic 3.5L ones.

But I'm curious how the torque and horsepower and gas mileage (in similar-weight vehicle) compare, and whether anybody has ever put an OM603 into a W116.

[1980sdga]

I had narrowed my MB search down to either an 86,87 300SDL or a 79/80 300SD.  The OM603 almost seduced me but the trap oxidizer and cracked head problems spooked me. Plus I like 116's better  

I think before I considered the cost and expense of an OM603 transplant I'd just look seriously at some performance mods for my solid old iron head  617.

If you read different internet forums most of the 116 300SD topics are, "My AC doesn't work" or, "My window won't roll down".

With the turbo 603's  its, "I have water in my oil" or "I think my head's cracked".

think that speaks volumes...

[jbrasile]

Agree 100% with Jon,

While the 603 is a much more civilized and powerful engine (148hp in the 300D Turbo and SDL) it does not come even close to the 617 as far as durability and reliability. The trap oxidizer is not the worst of its problems and because it is slightly more complex its operational costs are higher too. It's a shame because it is gem of an engine...

It's interesting to note that the M103 that replaced the M110 is also a much smoother powerplant but it too suffers from some cronic issues that have never afflicted 110's in the more than 12 years of its production run. Worn out valve guides, bad head gaskets, problematic idle, hard start issues, etc.... Fortunately or unfortunately  old school engines such as the 617 were built to last a lifetime if well looked after and they would be my choice over a 603 any day.

Tks,

Joe

[jjb-w116-hu]

hi Joe - what is involved in recon'ing a M110 engine?
am keen to get as much power out of the ol' girl as possible.

thanks mate

[jbrasile]

James,

You have to do the basics, full gasket set, all bearings, timing chain and guides, valve stem seals. Head should be overhauled as well.

Piston rings should also be replaced. If your engine is low compression, 7.8:1, you can change the pistons to give you 9.0:1 and recoup some hp that gets lost in the low comp setup.

Everything is available either from MB or the OEM's, we supply piston rings and pistons from Mahle.

Tks,

Joe

[1980sdga]

Speaking from US V8 experience...

I always had the rotating assembly balanced and had the connecting rods shot peened, magnafluxed and had them resized.  Not sure if the MB engines are externally or internally balanced...

Is it common to change cams in MB? We'd usually raise compression and change cams for a pretty decent increase in performance from our old Chevy V8's.

[jbrasile]

Jon,

I have limited experience with MB rebuilds, have never actually done one of mine but a friend reconditioned his M110 last year so I kind of know the basics. As far as I know you usually don't replace camshafts for more performance as you would  with an american V8. Injection tweaks, higher compression pistons or even an over bore and stroke are usually the way to go with MB engines.

Tks,

Joe

[jjb-w116-hu]

hi again Joe - my m110 engine seems to crawl very slowly uphills and as i dont have a tachy i cant see what its doing but somehow i am sure i should get more power of of a 2.8 litre engine.
as you know early stages of restoration as it is my daily driver, but just wondered what is the best place to start to see about engine power overall or test to see if im just expecting too much, still beautifully smooth at speed but i seem to limp up the first couple of inclines on way to work each morning ... cheers James

[jbrasile]

James,

First thing to do is a compression and leak down test to see the condition of the internal components both in the lower and upper parts of  the engine. A high compression carburated M110 will put out 160hp and while it is not exactly a torquey engine at low rpms it is no slouch either. However going up a hill in 2nd gear on an automatic is not exactly a sprint...

Usually M110's will need a valve job at around 120000km, that entails in removing the head, replacing the valve guides re working the valve seats, changing the timing chain, guides, tensioner, etc...

Before you do anything, have the compression test done, otherwise you'd be just guessing.

Tks,

Joe