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w168 160 petrol
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Discussion Starter #1
Hello,

I have been trying to find a (detailed) comparison between the two inline 6 engines used in the w126. No luck so far, so I am asking here. Since this is the W126 forum, please do not get the m104 involved, there is plenty of information about that to be found elsewhere. So in particular I am interested in the following:

What is the improvement of the m103 over the m110?

At 3.0L it actually produces less power than the much older m110 with its 2.8L. This is not typical for modern engines to be weaker than their older cousins. Is the SOHC an improvement over the DOHC?

What oil and gasoline does the m103 take?
I read that the m110 is happier with motor oils with high zinc content (not so easy to source now). More modern engines do not not seem to mind running 'leaner' motor oils. In addition is the m103 designed to run on unleaded fuel (95 octanes)? The m110 just handles lead free gasoline well, however, I do not think when initially designed this was taken into account?

Longevity and maintenance?

I do not need to ask you about the ability of a properly maintained m110 to run for MANY kilometers, so how does the m103 fare? Both have a cast iron block, so overhaul seems to be pretty straightforward. Does the m103 need valve adjustment and timing chain/tensioners replacement at similar intervals as the m110? Also on the few videos of the m103, when throttled hard the whole engine cants to one side, so any known problems with the engine mounts? Crumbling wires with the m103 or this is a m104 problem?

Stock performance modifications?

The m110 has an AMG version which involved just a different head/camshaft, etc for additional 25hp at the top end. (Extremely rare)
The m103 had a similar AMG modification as well as one with an AMG crankshaft, etc, the whole deal. Are those AMG mods easier to find? Particularly the AMG head/camshaft seems like a very quick DIY job.

Thank you in advance!
 

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1973 W107 350SL, 1985 W123 280TE, 1983 W123 230E, 1996 W202 C280
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457 Posts
The m110 was a bullet proof beast that has good potential for tuning. the m103 was good at wearing cams and blowing head gaskets and in my understanding is harder to tune, Ive never liked the 103 but love the 110.

The m103 was pre bio-degradable wiring coatings so no problem there.

The 104 is the most powerful of the 3 by a decent margin, especially in the 3.6 and 4.3 amg variants :D

If you want detailed technical specs please pm me.

Rgds,
Reuben .S
 

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W124 400E, W126 500SE
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971 Posts
M103 when maintained well will make you happy - an old W124 300E with manual tranny could outrun almost anything when the driver was insane enough :)

What is the improvement of the m103 over the m110?

slightly higher torque, simpler engine (SOHC x DOHC), hydraulic lifters (no valve adjustment needed), much better MPG (in W126 at least)

What oil and gasoline does the m103 take?

Unleaded fuel only. Not sure about exact oil specs, MB 229.3 methinks?


Longevity and maintenance?

Early models had failing camshafts, it was later corrected under warranty. You can be unlucky enough to get one but I have never seen one fail this way here...
Headgasket leaks are very common, but not that extensive, most people just ignore the oil leak. Replacing the gasket is not a hard job (not saying it's an easy one though).
Unless you overrev it badly it is very durable, I've seen motors with 500-800kkm on the clock and they still worked. Not sure what was done on them though (nothing, probably? :))


Stock performance modifications?

I know people replaced their KE-Jet control units to get a torque boost (you can swap in an ECU from G-class to gain torque, not sure what other options are there), that's easy. You can turbocharge it. Can't tell much more because most are happy with the stock performance.
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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2,282 Posts
The M103 is a free revving and "torquey" motor...published numbers 177HP/188Torque on US spec motors seem low compared to real world performance when the cars were new...
 

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87 300SL "Roadster" 86 420SEL "Limo" 89 420SEL The "New" Limo 87 190E 2.6 fact bodykit
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The 104 is the most powerful of the 3 by a decent margin, especially in the 3.6 and 4.3 amg variants :D

If you want detailed technical specs please pm me.

Rgds,
Reuben .S
I'd love to know a little about the AMG 4.3lt variation!

The 3.6lt I know but 4.3lt in a I6 M103...WOW!:eek:

I thought the AMG 4.3lt was a V8!:confused:

Cheers
 
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