design - Land Rover section


Converting a Series Land Rover to a Mercedes 617 turbo diesel engine

By Robert Davis
From a posting where he describes the conversion kits he sells

For more information, contact Robert Davis at


Back in the early 1980s had a job that allowed me to travel to places like Malta and Greek governed Cyprus. I saw several Series IIA Land Rovers with Mercedes 4 cylinder diesel engines. At the time knew little about the Mercedes diesels and don’t remember exactly which engine, but they all looked similar to the OM616.

All were based on an adapter similar to what Mercedes Jim developed years later with a custom adapter about 2 inches thick sandwiched between the Mercedes rear aluminum casting and the Land Rover transmission bellhousing. I was told that the stock Mercedes flywheel was used.

Fast forward to 2002 when I bought our 300TD Wagon and was very impressed by the performance and outright reliability. About that same time did several one off diesel conversions with Perkins Prima, Isuzu, Diahatsu, and Rover 200 & 300 TDIs. Also decided to eventually phase out the GM gasoline engine conversions I was building at the time.

In 2007 started doing research to build a Mercedes conversion. At first was going to use a modified version of the OM616 4 cylinder complete with turbo, but the costs were not practical (to do it right) because it required a complete remanufacturing: drilling the block for the oil squirters, using the correct version of OM617 turbo diesel rods and pistons, and changing the IP to have the same characteristics as the OM617. There was also the issue of making a custom exhaust manifold to mount the turbo like I did for the Diahatsu engines.

In 2008 started looking more closely at the OM617 and asked lots of people lots of questions including Mercedes Jim and 2 other friends who had also successfully completed OM617 conversions in their 109s using kits they bought in Germany that may have been originally for a Unimog. All these installs had several common factors that I wanted to avoid. They required oil pan modifications and were based on the stock Mercedes manual flywheels that are somewhat thick. With any conversion, the clutch has to be spaced the correct distanced from the clutch release bearing and when added to the flywheel thickness determines the adapter width. Some of the conversions also required the removal of the stock oil filter housing with the correctly regulated flow through the oil cooler lines.

So continued to do a little research here and there to overcome what I determined to be the conversion issues of mounting an OM617 in a series IIA, III, 90 and 110.

Determined that in order to build a kit that could be easily installed the 4 major obstacles to overcome were to build a custom oil pan from scratch that eliminated the front diff clearance issues, locate the engine so the stock oil filter housing could remain in place, and have the adapter much thinner to allow the engine to fit in a series IIA or III 109 or 88 engine bay without having to cut up the radiator support and/or use some custom radiator. In other words, build a kit that someone can install in a weekend and drop off for a custom exhaust on Monday and drive it home that same Monday evening. Indeed a tough "nut to crack".

After building several prototypes and improving each one, was finally able to overcome all of these obstacles and am making the second install in a 110 this weekend. Then will make the second install in an 88 the first weekend in September. When fitting an OM617 with my kit into an 88 and 109 that originally had a 4 cylinder, the engine falls short of the stock radiator by about 1/2" - 5/8” clearance which leaves enough room to slip a fan belt between the back side of the thinner Series III stock radiator and the nose of the OM617 water pump. The stock Rover gearbox and transfer case remain in their original location.

Anyone who broadly makes the statement that the OM617 won’t fit between the stock Series transmission and the stock Series III radiator has clearly not seen my new conversion kit that does fit into this space. However, if you bolt the adapter I saw in Malta onto an OM617 or the adapter Mercedes Jim made (which was excellent work in it's day) then the total length of the OM617 with this much thicker adapter is too long for the 88 and 109 engine bay and won't fit in this same space where my kit does fit.

Let me summarize to be perfectly clear: using my kit, you can remove a stock 2.25 Rover 4 cylinder out of a 109 or 88 and bolt a OM617 in it's place without changing anything (except for the thinner series III radiator if you have the thicker IIA radiator) as a 1 for 1 swap. In the IIA or Series III 88 & 109 (that left the factory with a 4 cylinder engine), there is no need to use a Rover 6 cylinder bulkhead or any additional modifications. The engine bolts in just like the 4 cylinder GM engine conversions I built for over 25 years. This is one of the key points of this post.

During each install started with the donor vehicle stock engine (88, 109, 90 or 110) in place at 5:00 pm on Friday and using only hand tools. In all cases were able to remove the engine from the Land Rover along with the exhaust system, drained the fuel tank, and completed other tasks Friday evening stopping work at 10:00 PM. On 8:00 AM Saturday started with the built up Mercedes engine with the custom oil pan in place with the custom adapter, custom flywheel with Mercedes ring gear, Land Rover 9.5" clutch, and custom motor mounts. Because the motor mounts bolt directly from the engine and mate to the stock chassis, there is no custom welding or cutting. In the 90 and 110 all the stock Mercedes ancillaries fit without any clearance issues. On the 88 & 109 all that I used was the Mercedes alternator with a custom mount that placed it up where the PS pump originally was.

In each case my install (in an 88 and 110), by 5:00 PM on Saturday the OM617 engine was in place and could be running if you used the manual shut off or jumped the glow plugs (if the controller was not hooked up). Sunday installed things like an electric cooling fan, any extra gauges (like oil pressure or boost), and vacuum shut off switch. The conversion is not difficult (about the same as the GM), but took longer because of the electric fan, vacuum shut off switch, glow plug controller (which is an easy to install kit option), and other odds and ends. This kept me working Sunday from 8:00 AM to about 1:00 PM when in all cases satisfied the weekend install with time to spare.

Having the correct oil cooler with lines that match the stock Mercedes oil cooler housing, radiator hoses, accelerator linkage, and so on makes for an easy install. On the 90 & 110, the custom power steering hoses were bolted in place and connected to the stock Mercedes PS pump.

In closing, it has been a long, expensive, time consuming journey, but the engine fits in the stock location without cutting or welding into an 88 or 109 that originally had a 4 cylinder and also fits nicely in a 90 or 110. A custom oil pan is required, but a custom oil pickup is not with the latest "production" version. We also have a separate kit with a longer adapter to mount the OM617 into a 109 that originally had a Rover 6 cylinder and have one of these 109 conversions up and running as well.

Performance is very good and the engine is in the correct torque range to mate in harmony with the stock transmission and differentials. With so many activities, have little time for bulletin board forums, but just wanted to make this post to provide some accurate information about the upcoming kits that will be available in the near future.



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