For overall simplicity, high number of production years (easy to find good used parts for cheap), the M103 wins hands down. The M104 is more refined, but has more expensive issues (wiring harness), in addition to the head gasket issues with both engines. The M104 feels a lot faster, but in reality, I think it's within .2-.5 second 0-60 difference between the M104 and M103. M104 feels faster due to torque down low that the M103 lacks. Otherwise the M103 seems to rev more freely. The 94/95 HFM cars were also heavier than the M103 cars, so that negated a good portion of the extra power.

Also, nothing can beat the sound of a redlining M103, I'm sorry. The M104 is too quiet and modern sounding compared to the "screaming" M103 for my tastes. Tunnel blasts are waaaay too much fun in a otherwise stock drivetrain/exhaust 300E. ;)

Totally agree...especially if you've had the experience of driving a new M103...!!!

What must also be considered is that the M103 was delivered with a 3.07 rear.
This compensates for the power advantage of the M104.

M103 much more simplistic and easier to maintain then a M104...
No variable cam timing, spark coils, wiring harness, etc...

Only one ignition coil and no biodegradable wiring harness in my M104.

RayH

My guess is that you have the transitional early M104 still using the CIS-E?
The majority of M104 in the USA are the later versions with three spark coils, HFM and "green" wiring harness.

The 2.6L variant of the M103 came with a 3.27 rear end, while the 3.0L version had the 3.07. At freeway speeds, I'm looking for another gear to shift to with the 3.27, but from a stop, the 3.27 makes sense for the smaller motor.

Agree the 260E was the only USA W124 with the 3.27 with the 300E W124 and the C124 using the 3.07.
The 300TE S124 also used the 3.27 with lower ratios up to 3.67? available in Europe.

Not a chance.

The M104 is so much better off the line. It got 2.65:1 gears because it has the muscle to pull them, and went to a 1st-gear start like it should have, smooth and fast. My daughter's doesn't have ASR, will smoke the tires from a start without touching the brakes, try that in a M103 car, ... the extra hp and torque is quite evident (I've had 3 M104s and 2 103s).

Couple that with the improved fuel mileage, low-RPM torque to eliminate the downshifting/revving, and the simple fact that the wire harnesses on all of the early '90s cars with either engine degrades, it's a better engine.

Now when you add the Euro-style all-glass headlamps instead of the M103 cars' crappy plastic-fantastic ones, the better cluster lights of the later cars, the all-up and all-down windows/sunroof of the '90s models, the '90s models' better seats and interior, the M104's larger 4-puck brakes replacing the 1-puck floaters, the updated 2-color tail-lamps with rear fog and clear front corners, updated front and rear trim/hood/trunk, clamshell storage armrest and tambour-door storage box, ... etc., it's a much nicer package.

I've had both, and the M103 car is an excellent car. However, given the choice between a '94/'95 and an earlier car, no comparison and I'd never go back, the M104 cars are IMO that much better.

<edit>

Looked it up, even with the taller 2.65:1 gears the extra 40hp/41lb-ft was still good for .4seconds 0-60 (8.0 from 8.4).

You're not wrong there ...
 

Spot on. I have the early M104 and if you boys want screaming, this is the motor. It's red line is at 7000 rpm and it sounds great in a tunnel or alongside something solid.

Coupled with a 5 speed auto box, it performs well and will manage 30 mpg (UK) on a 80-90 mph run.

Good motor.

RayH

A few years ago tour Mercedes Enthusiast magazine referred to the CIS 104s as "cobbed together", a rush job to get 4 valves per cylinder on the market in response to Japanese offerings. I had one in a 1990 300SL that needed a full valve job at 45k miles. It still has all the CIS problems - enigmatic fuel delivery system, with very expensive components, primitive diagnostics, inferior fuel economy - plus anemic low end power (worse than 103). A wiring harness is utterly insignificant by comparison - especially considering what you get in low end driveability. This wiring harness obsession is kind of weird - not that expensive and they've almost all been replaced already.

I like my 1999 m104 30 mpg highway.303 hp with easy mods to engine instead of stock 228.

Hmmmmmmm ...
 

I can only assume you had a duffer. Mine has good fuel economy and, at 370K Kms is on the original wiring loom, motor, gearbox, etc. The only work on the engine was the head gasket at about 170 K Kms. All the costly CIS parts and electronic controllers are original and in exceptional condition. Oil pressure is as new and the only issue is a cold start clatter for about 3 seconds as the hydraulic tappets pump up. It starts first time every time whether at -20C or +35C.

And the mechanical MAF is original which is more than can be said for most hot-wire MAFs.

As for low end torque, agreed, the engine is a screamer so I make it scream.

I'm thoroughly satisfied.

RayH

It's fuel distributors and EHA valves that are the weak link and common problem. Hot wire MAFs are bulletproof, often good for the life of the car. But the later 104s are not hot wire, but rather hot film, which still isn't bad, normally good for around 100k and cost less than $200 now.

I'll take my CIS-E M104 over any M103 or HFM M104.


Best of both worlds.

UK mag "Mercedes Enthusiast" just did a buyer's guide for the full range of C124's..

Oddly enough the early M104 like you have was quicker to 60 then the higher torque later M104.

The M103 was about .4 seconds slower to 60 which is not bad considering the power disparity :)

Well!
 

Bulletproof! Why are so many people replacing them, then?

My original fuel distributor is still distributing like a good-un. I did replace an EHA due to a leak. The replacement EHA was from a 1987 300TE 4-Matic and it's still going strong.

So, the EHA in my car is still giving service after 24 years and the fuel distributor after 20. Weak link????

RayH