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Our source of info have been Unimog-friends (thanks to all of you), books and buying and disassembling various engines. We had no time so far to do the actual swaps yet, we want to and will as time goes on. However, we took measurements and estimates for size and would it fit ???, etc...  If anyone ever feels that we're wrong, please call us (Klaus (408) 336-2300) and we will correct or amend it.

Our S-404 engine swap corner :

The 1st question is a classic one : To Diesel, or Not to Diesel

The Gas engine is the more traditional one and most people believe the more powerful one too. That's mostly the case, except for the newer Turbo-Diesel engines. The peak-power is still less than on a gas engine, but the usable power range of a Turbo-Diesel can be a better match for an Unimog, than the power band of a hot-rod gas motor. (unless you want to climb a hill in 2nd gear, redlining the engine at 6500 plus RPMs, well you will fishtail like a Formula-1 racecar in the rain, but you might also inherit a racecar-live-expectancy for the engine and drive-train, happy wrenching to you) !!!

There are a few basic issues related to S404 engine conversions : Size and Fitness

bulletIt has to be an engine with the in/ex-take manifolds (both) on the passenger side. Absolutely no room on the driver side. This rules out cross-flow heads like the newer dual-cam gas engines (M110, etc...). It also rules out the OM352 family of engines because the in/ex-take ports reside on the driver side.
bulletThe length of the engine is very critical too. The 2.8l M130 hits the limit for the bore-diameter for its 6 cylinders (if you stroke it, philosophically speaking, you can get more displacement). The other solution was to drop a cylinder and create a 5 cylinder Diesel 3.0l OM617 (bigger bore but less cylinders, ??? ideal would be a 2 cylinder with 5 liters per jug ???). The OM352 faces the same length problem (6cyl. and 5.7l).
bulletThe only qualifying gas engines are the stock 2.2l M180 (hi or low compression, single or dual carbs).
The 2.5l M108 (older) or M114 (newer) with cylinder-pairs 1+2, 3+4, 5+6 Siamese'ed together for length of the engine reasons is very similar to the 2.2l M180. (Siamese'ed means no coolant flow between the adjacent cylinder walls)
The 2.8l M130 engine (stock in some S404.0 civilian Unimogs, but low compr. head) is the most popular one, but all 6 cylinders are Siamese'ed to keep the same length as the 2.2l and 2.5l engines.
Notes: Only the carbureted version of the gas engines will fit, NOT the fuel injected models (the injection pump is located on the driver side and there is NO room for it).
The flywheel of the M180 is part of the crank-balance (external balance). The M108, M114 and M130 have a neutrally balanced flywheel (internally balanced crank), but require the M180 Unimog flywheel for clutch assembly reasons. You need to re-balance the Unimog flywheel by adding (welding), or by turning off the excess with a lathe (both approaches have been done).
You also need to use the M180 Unimog oil-pan (bell-housing support), which requires some minor machining inside to clear the bigger crank.
bulletThe 5 cylinder 3.0l OM617 engine will fit with major modifications and is still an ideal candidate. The injection pump is on the driver side, so it needs to be tilted by 13 degree to clear the drivers right knee. The oil-pan needs a 13 deg. wedge welded in, to make it flat again (cosmetics). The engine tilt and the significantly higher torque (Turbo-Diesel) requires a custom clutch-bell-housing and a steel motor interface plate (standard aluminum). You also need to shop for a truck-flywheel (passenger cars were mostly automatic) and use the clutch assembly from the MB G-Wagen. This is a short stroke diaphragm spring type which requires the clutch lever on the bell-housing to be lengthened. The other clutch option is to go with a manual tranny passenger- cars flywheel (rare, mostly Europe), do some machining and make the standard S404 clutch fit. You also need a custom front-engine-mount. There are a few final fights with getting the van belts aligned and the cooling and diesel-return-line plumbing squared away, along with modifications of the passenger-side engine cover. Well, I almost forgot to mention that it's recommended that you replace the entire exhaust system with a new (custom) high flow because of the Turbo requirements. OTHER THAN THIS, IT'S SUPPOSED TO BE FUN.
bulletAny other engines, not meeting the above guidelines will somehow fit, but it will be very very custom, with the radiator up front, underneath, next to it..., the individual imagination of the converter is the limit.
bulletAlso, please stay away from diesel engines with less than 110 hp and gas engines with less than 125 hp. Unless you want to plow your fields and leave the highway for the real cars.

We will come up with power / torque charts, but it takes a while to get them. Despite the enormous effort for the 5cyl Turbo-Diesel conversion, it seems to be a real good choice, because of the MPGs and the lower torque band (We can't speak for or against noise pollution within the cab yet, Diesel-knock)



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We would be very happy to hear from You.

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