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]

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.

[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]

Teriann, that all sounds great. You're getting much better power, and better feul economy as well. This is what I am after as well, and am hoping the diesel will fill that roll. I'm not exactly sure of the math to figure out a realistic cruising speed with the om617. I will be using a series 3 transmission, the stock transfer case, but also I have a ROVERDRIVE fitted. I don't remember my tire size, but I think they are a bit bigger than stock.
With my 2.25 I loose lots of speed going up steep hills, but everyone that has driven with me that knows rovers has commented they have never felt this much power from a 2.25. Still, we all know that's not saying much. In the summertime I run a soft top, and I don't carry a whole lot in the truck, so with the little weight I have in the truck, I find it pretty peppy, and can boot around town with plenty of get up and go (for a land rover) but the upper end feul consumption is so bad. I would be lucky to get 12mpg on the highway, with a very small amount of city mixed in.
Does anyone know what I could expect as a highway cruising speed with my setup, and an om617?

[Moose]

Does anyone know what I could expect as a highway cruising speed with my setup, and an om617?

My Series 3 88 has a 2.5 NA diesel in it, stock gearbox, 235/85-16 tires and a Roverdrive. It will cruise along the 401 at 100 km/h but is happiest at 90. The 2.5 is about equal to the 2.25 petrol engine performance wise so it bogs down a bit on hills too. Over all though, I am very happy with the engine and it returns about 25 mpg mostly city driving. Don't know what the power output of the om617 is but it's got to me more then the 2.5 NA so I would suspect you should a get fairly decent cruising speed with your set up.

Brett

[Alk-3]

My Series 3 88 has a 2.5 NA diesel in it, stock gearbox, 235/85-16 tires and a Roverdrive. It will cruise along the 401 at 100 km/h but is happiest at 90. The 2.5 is about equal to the 2.25 petrol engine performance wise so it bogs down a bit on hills too. Over all though, I am very happy with the engine and it returns about 25 mpg mostly city driving. Don't know what the power output of the om617 is but it's got to me more then the 2.5 NA so I would suspect you should a get fairly decent cruising speed with your set up.

Brett

Thats great mileage! I'd be happy with that. I think the om617 is rated at 120hp, but I don't know the rpm range of it. It is supposed to be able to reach higher rpm's than many other diesels, but that's not much of an indication really. I'd like to know how it compares to the 2.25 I have now.