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The 300 24v M104 Engine

Dan21st July 2016

The M104.980 engine was fitted to the W124 range and the pre-facelift R129s. The engine outputs 231bhp and 270 Nm of torque from the 3.0 unit and was an upgrade from the 12v version, which produces 188bhp and 255 Nm of torque. If you are looking for a car that likes to rev, the M104.980 redlines at 7,000 in every gear and to get the most out of the engine, you must rev it. Peak torque and power figures are around 4,000, where the engine takes a steep climb in the torque curve and blasts its way to the red line.

Why Choose the 24v 300 over the alternatives such as the 300 12v, 320 and 280?

1. The 24v outrevs the others and if  you are a spirited driver, the engine will scream its way to 7,000 revs with a great sound track
2. The earlier 300 24v (and 12v) do not suffer from the well known biodegradable engine wiring loom, whereas the 320 and 280 do, which is not cheap when they go wrong!
3. Greater BHP and Torque than the 300 12v and 280 but similar bhp and less torque compared with the 320

Drawbacks of the M104 300 24v

I may be slightly biased as I own a R129 300 24v SL and think its a great car, however it goes without saying, there are some drawbacks

1. Torque – Low down the rev range, there is very little of it. The 124 and in particular the 129 are heavy cars and if you prefer wafting around, the 320 has low down torque which helps get it to speed/off the line without reving the engine out
2. Moisture in the Distributor – Very common in these engines in particular, which causes poor tick-over, poor fuel economy and hard starts. By personal experience, the distributor only suffers from moisture when left unused for a months on end. If you plan on only getting the car out for the summer like I do, let the car run for around 20 minutues, switch it off, dry the distributor cap and off you go.
3. The 24v engines have complicated EZL’s (ignition modules) which can break down with age. A replacement unit will not be cheap. The EZL is bolted to the inner wing, make sure that it is secure and has plenty of heat sink paste. underneath.

To conclude, the 24 valve engine is a great unit for those sprited drivers and it also has great tuning capabilities. The engines are supposedly capable of 700+ bhp and many people have converted them to twin turbo’s with kits such as the mosselman twin turbo kit. If mated with a manual gearbox, there would be endless fun and it would see off many competitors at the race track (and traffic lights!). If you plan on going for relaxing drives where you waft around, do not go for this engine but go for the 320.