Is possible to make the change. I have a W111 220 Sb originaly with gasoline 6 cilinders engine and many years ago an W115 240D diesel engine was fitted. No problem with the room, because the diesel 4 cilinders engine is shorter. You´ll need any modification on the electrics for the glowplugs, exhaust and intake manifolds and you´ll have to enlarge the driveshaft. No problem to connect the gearbox to the new engine

The problem of this modifications is that if you keep using an 4 gears gearbox with the short rear axle (4.01:1) of the 250S, you will get a tractor with strong but short accelerations (due to the aprox. 4000 rpm limit of the diesel engines compared with the 6000 rpm of gasoline engine) and the final speed will be no more than 120/130 km/h with the engine "screaming".

In Spain this modification was very common and useful. Some of this cars keep running with no problem, with economical use.

Best regards.

Manuel.

Spain.

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´60 W111 220b
´63 W111 220Sb
´75 W115 240D 3.0
´78 W123 300D
´88 W124 200D