Mercedes OM617

[Alk-3]

Hi everyone. I was hoping to open up a bit of a dialogue about the Mercedes OM617. I am very seriously considering doing a swap with the Robert Davis kit. The kit apparently comes with everything needed to swap the motor into my land rover, but requires a pusher fan, and requires a swap to a thinner series 3 rad.
I was looking for any and all thoughts on this swap, and what kinds of things I can expect to run into.. maybe some comments on how to choose a suitable engine etc.
Also curious about performance, and how my truck will feel different from it's current state, which is a fairly strong 2.25 petrol.

My truck at the moment is a very reliable unit in general. I drive it as my only vehicle, and have only been stranded once with a cracked head (swapped head gaskets, and opened up a pre-existing crack). all other minor issues have been solvable on rout.
The reason I'm considering the swap is layers deep:
- I get terrible milage out of my truck, and with the amount that I drive it, I spend a huge amount of fuel. (up to $400 per month)
- power is pretty bad.. good for a 2.25, bad for everything else on the road. This is less of a concern than the next point…
- the highway miles I put on the truck (I think) is putting a lot of strain on the old engine. I might drive for 8 hours at 100km/h each (or every other) weekend.. I would rather not kill this engine, so I'm thinking if I swap it out now, I will still have the original engine in good condition should I ever want to do a full restoration back to original.
- diesel fuel in general is better for me. I have a tractor than uses it, and have it around most of the time
- the Mercedes om617 is apparently a great motor that if cared for can get many hundreds of thousands of miles on it. I plan to keep my truck forever, and this engine sounds like a good candidate in that regard.

if I have to boil it all down, the real main reason for the swap is so I can use the truck without worrying that the old gas 2.25 is about to blow. Right now I am constantly worried I'm stressing the motor, and so I end up just not doing the things I would like to do with the truck.

[I Leak Oil]

Mercedesrover will be able to provide you with all the first hand knowledge you could ask for about the Mercedes swap less the RD kit.

[TeriAnn]

Instead of an SIII radiator that sits behind the front cross member you can use an aluminum cross flow radiator that sits on top of the front cross member, gain more space and more cooling. Gryphon has a stock one that some folks with engine conversions have been using. It does mean cutting down some of the baffling on the radiator bulkhead and coming up with a new horn mounting location.

I am using an electric radiator fan from a 1990's Mercedes V8 sedan. There seems to be one standard size that came with the V8. It is largest fan that will fit vertically behind the grille. It is high quality Bosh & only cost me $40 from my local wrecking yard.The Mercedes mounting struts got reused in my application. The fan sits in a shallow inverted U channel bolted to the front cross member.



When it came time to get radiator hoses I bought a pair of flexible heater air duct hoses and bent them into the shape and lengths I needed. Then I went browsing at an auto parts store looking for hoses that fit the pattern. In each case I found my needed hose inside the shape of a longer hose. I brought the hoses home and cut out the part that matched my pattern. Your alternative of course is the accordion flex radiator hoses but they do not flow nearly as well as a smooth hose.

[Alk-3]

Instead of an SIII radiator that sits behind the front cross member you can use an aluminum cross flow radiator that sits on top of the front cross member, gain more space and more cooling. Gryphon has a stock one that some folks with engine conversions have been using. It does mean cutting down some of the baffling on the radiator bulkhead and coming up with a new horn mounting location.

I am using an electric radiator fan from a 1990's Mercedes V8 sedan. There seems to be one standard size that came with the V8. It is largest fan that will fit vertically behind the grille. It is high quality Bosh & only cost me $40 from my local wrecking yard.The Mercedes mounting struts got reused in my application. The fan sits in a shallow inverted U channel bolted to the front cross member.



When it came time to get radiator hoses I bought a pair of flexible heater air duct hoses and bent them into the shape and lengths I needed. Then I went browsing at an auto parts store looking for hoses that fit the pattern. In each case I found my needed hose inside the shape of a longer hose. I brought the hoses home and cut out the part that matched my pattern. Your alternative of course is the accordion flex radiator hoses but they do not flow nearly as well as a smooth hose.

Great advice Teriann. Thanks for tht!
Would you care to comment on the drivability, fuel consumption, and power you have experienced after the swap?
The rad swap is great advice. I was a bit concerned with clearance in the front. I'm really finicky when it comes to maintance on my truck, and some space in the front will make frequent valve adjustment a little easier (turning over the engine with the crank bolt).
I've had to do the same heater hose hunt for my tractor, and agree the according style would be a last resort.

[o2batsea]

I think she's got a EFI Ford 302 in there, at least last I knew. Whatcha running for a ECU TAW? A9L? That's not exactly a super fuel efficient engine, but then again it has to haul a heavy truck around. She can of course tell you what it's doing, performance wise.

[TeriAnn]

Engine - Ford 302 from a 1969 Mustang

Cylinder heads - Aluminum Airflow Research The ones with the small valves and small passages. They flow best under 3000 RPM of any stock or aftermarket cylinder head. Most all the "performance" cylinder heads flowed worse than standard stock below 3000 RPM. With Aluminum heads, a Ford 302 is about 50 lbs lighter weight than a stock 2.25L LR petrol engine. With Al heads a Chevy small block is about 50 lbs heavier than the LR engine.

CAM - Custom COMP cam This cam is designed for low end power and fuel economy. It is basically a truck towing cam for a flat tappet 302 with SHO timed EFI.

Intake - 1991 Mustang EFI with custom fuel rails to allow the fuel to come in from the right rear of the engine. Otherwise it is stock for a '91 Mustang. All fed from a Donaldson 2 stage earth mover filter system.

Fuel pump - Late 1980's pickup external fuel pump

ECU - haven't a clue. It is what the auto parts store gave me when I asked for a ECU for a 1991 Mustang GT 5.0 with four speed. I'm hesitant about going for performance add ons. Performance parts usually add performance to the high RPMs by stealing it from the low RPMs where my engine lives.

History:
With SIII LR engine & solex - about 15 MPG highway 8 MPG city
SIII LR with Rochester - About 15 MPG highway, 7 MPG around town
Ford 302 with 500 CFM Carter AFB jetted for economy, About 15 MPG highway, 7 or 8 MPG city
Ford 302 with Mustang EFI, About 17 MPG highway, about 12 to 14 MPG city.

Conclusions: the highway speed is more limited by the truck highway speed and the truck's air resistance. And for my truck 15-17 is about as good as it gets for old school carb or EFI petrol.

EFI is MUCH better at stop & go driving than a carb. That's where my real fuel savings comes from.

And of course the 302 has more power at idle than the 2.25L has at peak so i can go the speed limit uphill. With the LR engine there were sections of Utah highways where I could not go as fast as the minimum posted speed limit. Merging into traffic on freeway on ramps is not a concern nor are big rigs behind me on steep highway hills.

With the Ashcroft high ratio kit (which my engine easily handles) 65 MPH is 2650 RPM & 70 is about 3000 RPM. Wheel alignment within spec is a must at those speeds so no do it yourself alignment. My gearbox low range first is just a tad over 50:1 at the axle. Low range first on a stock Series truck is a tad over 40:1. I prefer to go last down a hill so I don't get run over and cruise the highway with the V8 Defenders.

99% of my driving is done below 3000 RPM and even with the V8 & gearing I still seem to cruise at around 60 MPH (2500ish RPM) when I'm not looking at the gauge.

Driving with a tach my SIII engine was happiest cruising in the 3000-3300 RPM range. The engine held its power on hills down to about 2400 RPM then rapidly lost power below that. So on a hill 2400 RPM was my shift down point for maximum speed up the hill. The engine would run smoothly down to about 800 RPM but there was no usable power below about 1500ish RPM. Power fell pretty quickly below 2400 RPM.

V8s like to lug along at lower RPMs. The engine feels happiest around 2300 to 2500 RPM. It still pulls well at about 1000 RPM and when convoying with others off road I'm frequently from around 1000 RPM and 1800 RPM

[Alk-3]

Mercedesrover will be able to provide you with all the first hand knowledge you could ask for about the Mercedes swap less the RD kit.

Yes, I've read his thread on expedition portal, and am amazed by his work. I know he used a different transmission, which I think complicated things more than the kit I plan to use will, but in the end he has a better setup as well.

[rdavisinva]

Hi everyone. I was hoping to open up a bit of a dialogue about the Mercedes OM617. I am very seriously considering doing a swap with the Robert Davis kit. The kit apparently comes with everything needed to swap the motor into my land rover, but requires a pusher fan, and requires a swap to a thinner series...

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 portion about 2 or 3 inches long sandwiched between the Mercedes rear aluminum casting (that is about 1.5 inches long) and the Land Rover transmission bellhousing. In all cases 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. For a few years 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 that 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 upgrading the IP to have the same characteristics as the OM617 turbo diesel. 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 originally been for the Unimog. All these installs had several common requirements that I needed to avoid. They required a 109 6 cylinder bulkhead, a huge undertaking to swap out for someone who had a 4 cylinder bulkhead making the conversion impractical for the average person. The stock oil pans were modified requiring both steel and aluminum welding and fabrication which is totally impractical for a conversion kit. All these earlier incomplete kits typically included only an engine adapter and an oil filter relocation adapter plate leaving the rest of the parts for the conversion missing. All had an engine adapter based on the stock Mercedes manual flywheel that is on the thick side. With any conversion, the clutch has to be spaced the correct distance from the clutch release bearing. The distance needed for the pressure plate is added to the flywheel thickness to determine the total length of the engine adapter. So a thicker flywheel essentially equals an even thicker engine adapter. All of the conversions I saw also required discarding the stock oil filter housing for a filter relocation adapter that routed the oil to an externally mounted remote oil filter via hoses. The stock oil filter housing has the correct temperature controlled oil flow to and from the oil cooler, something I vowed to keep.

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 or 110. If these issues could not be overcome, then a complete conversion kit for the average DIY person to install over a weekend would be impractical and the research would end with a "no go".

Determined that in order to build a kit that could be easily installed the 4 major obstacles to overcome were to eliminate the need for the 6 cylinder bulkhead swap requiring the dismantling and reassembly of the entire body, build a custom oil pan from scratch that eliminated the front diff clearance issues that the original pan has in both the Series and Defender style vehicles, locate the engine so the stock oil filter housing could remain in place, and have the adapter between the engine and transmission 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 a 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 home that same Monday evening. Indeed a tough "nut to crack".

Was it s "go or no go" ???

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 with 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. This is with the stock 4 cylinder bulkhead in place and the stock Rover gearbox and transfer case in their original position.

It's a go...

Anyone who says 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 were both excellent work years ago) 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 the key point of this post.

The goal of a complete conversion kit is to make the engine install no more difficult than replacing the stock engine with another stock engine, in other words a bolt in 1 to 1 exchange (less the exhaust system which is different).

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. On the 88 & 109 used the Mercedes alternator with a custom mount that placed it up where the PS pump originally was. The 90 and 110 install uses all the stock Mercedes ancillaries without any clearance issues in both RHD and LHD vehicles.

In both the 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 install kit option), and other odds and ends. This kept me working Sunday from 8:00 AM to about 1:00 or 2:00 PM that 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. For the 90 & 110, the custom power steering hoses were bolted in place and connected to the stock Mercedes PS pump.

In this thread, you asked if fuel savings could be realized with an OM617 conversion. I have talked to owners of 80s era Mercedes sedans like the 300D that save over $4,000 a year on fuel that burn Waste Vegetable Oil (WVO) in their OM617. The drawbacks they report are mainly concerns with cleaning the fuel and the time it takes to collect it from a local restaurant. Know a guy who bought a centrifuge and collects once a week and when in his shop, runs the centrifuge and gets pretty clean oil. So far he has not had any issues, but have talked to other people who had to replace injectors and the Injection Pump (IP) from using WVO, but this was after tens of thousands of miles driving free on WVO fuel. At our local pick-n-pull OM617 engines are about $300, and IPs are $50. You can't fill up a 2.25 gas engine from a grease dumpster, but the OM617 seems to run fine on WVO.

Performance is very good and the engine is in the correct torque range to mate in harmony with the stock transmission and differentials. In the early 1990s worked on an aviation maintenance management project with the USCG in Elizabeth City and got to be friendly with the reliability engineering crew. At the time was designing a new cam for the GM 3.0 liter crossflow conversion and did not want to overstress the transmission. The engineering shop analyzed a series IIA and a series III transmission making tests on the gears and shafts. The real limit believe it or not was the main shaft, but regardless, they reported that the max torque for the main box was around 185 foot pounds. In other words to maintain reliability you should not put an engine in front of the stock series transmissions that puts out a lot more torque than 185 foot pounds. I've seen people off roading tear up a series transmission with the stock engine, so driving technique definitely comes into play. The OM617 is near the top end, but still within this acceptable range.

In our 1985 110 pickup, am installing an intercooler. The OM617 has the stock turbo clocked to take the hoses with an inlet manifold from a 1976 Mercedes W115 300D, but that's a totally different discussion. The point I am trying to make is there are some inexpensive options to get just a little more power out of the OM617 Turbo Diesel, but am just getting into this area and am no expert, so for me it is just another learning experiment.

In closing, it has been a long, expensive, time consuming journey, but the OM617 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 conversions up and running as well.

Without the "pioneers" like Mercedes Jim and others who proved this conversion possible, I probably would have never bought our 1982 300TD wagon and would have never looked at using the marvelous OM617 that some claim will go for a million miles and is the most durable and reliable engine in the world. Thanks to all of you, especially Mercedes Jim who provided some advice back when I was doing research. He didn't always tell me what I wanted to hear, but "told it like it was".

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. I almost never check posts and only knew about this one when a friend sent me the URL.

RdavisinVA

[albersj51]

For clarification, you have a kit that will allow the OM617 (5 cyl MB diesel) to fit in an 88" series that came with the 2.25 4 cyl petrol or diesel without chassis/body modifications? If so, I am in heaven and will begin saving immediately!

[rdavisinva]

For clarification, you have a kit that will allow the OM617 (5 cyl MB diesel) to fit in an 88" series that came with the 2.25 4 cyl petrol or diesel without chassis/body modifications? If so, I am in heaven and will begin saving immediately!

Yes
Recalling a quote from Forest Gump: "That's all I have to say about that".

RdavisinVA