One reason I'm thinking it should bolt in is Wikipedia states "Also, 81 Unimog 404 were made with the diesel engine OM 615 (44 kW (59 hp; 60 PS)) for the Portuguese market." Unimog 404 - Wikipedia

 

The 615 and 616 should bolt up to the bell housing, the 617 will for sure. You will have to custom make the front motor mount as well as trim quite a bit of the drivers foot well to clear the diesel injection pump, the only way around that was lifting the cab 2" and using a custom bell housing that is no longer made that tilted the engine over. You can use the stock flywheel and clutch iirc, the engines are balanced with the flywheel and crank pulley installed so you will need to have the unimog flywheel zero balanced at a machine shop before running the engine or you could have some bad vibrations.

 

Wikipedia is wrong, the 404.117 (the only model with a diesel engine) was sold to Angola... which was a Portuguese colony until shortly afterwards.

The M180-powered and OM615-powered 404s used the same bellhousing, but the engine plate connecting the bell housing to the engine was different:

OM617a into Unimog 404.114

Hi everyone, Please stick with me. I've searched the forum a lot for info on this and, in my perspective, it all comes together like fragmented pieces of a puzzle, probably becasue my automative knowledge isn't very advanced, but I'm going to give it my best try! I have a stock 1963 404.114...

www.benzworld.org

The clutch used in a 404 has a different spline size then that used in passenger cars and there may be a difference in the flywheel pilot bearing size. A common engine conversion tactic is to use the original 404 flywheel on the replacement engine, as the crankshatf bolt pattern is often identical. However, depending on the version and age of the original M180, the engine may have been internally balanced (common today) or externally balanced (the flwheel is used for balancing the crankshaft and obvious out of balance by itself). So the 404 flywheel may need to be machined/balanced to use on passenger vehicle engine.

1.9 ALH TDI swap into 404.

Hey. I recently bought my first Unimog. I plan to drive it a bunch around town and to trails 20-40 miles away via the interstate, up a pass. I live surrounded by steep hills and I hope to drive it weekly this winter / summer. I chose the ALH VW I4 1.9 ALH, because: It fits with minor...

www.benzworld.org

That being said, several people have successfully swapped OM615/6/7 engines into a 404. It takes a bit of fabrication and rework to handle the injection pump/exhaust/front engine mount/etc. If you intend to use the 404 on road, I would suggest looking for a OM616 or 617 instead as the 615 is quite anemic, even compared to the original M180.

 

Don’t wast time on putting in an engien you won’t keep. Get a fresh M180 or M130 and be done. If the trans needs swapped oh well.

 

Much thanks to all for replies, I think I'm going to hold off on OM615 and keep looking for a running OM617 in my price range.

I usually do build threads on my projects, is that something this board supports, and members input on. I'm also a member of Pirate4x4.

 

There are a number of build threads on BW, both OM617 conversions and others engines. Like all build threads, lots peter out without a finish, though some go to completion. Unfortunately... the BW forum search tool sucks pretty bad... I suggest just using Google to search BW for threads with a "site:benzworld.org" plus the terms you want to find.

Google Search

Also, see Victorbart's Youtube channel for what a quality OM617 conversion should look like: