Diesel Conversion for Range Rover Classic

New Engine In PlaceIntroduction
Finding the Right Vehicle and Engine
Measuring Up
Machining the Adapter Plate
Making a Flex Plate Adapter
Fitting the New Engine In
Leveling the Engine and Adapting the Mounts

Test Drive Results
More Information

Photo at Right: Isuzu Diesel Engine in place in Gavin Reynolds' 1991 Range Rover


In most of the world, for good reason, diesel engines are common on Range Rovers, but in North America it has long been gasoline (petrol) only, mainly due to government regulations restricting engine emissions. Gavin Reynolds of Manitoba, Canada, recently did a diesel conversion on his 1991 Range Rover Classic using a 2
.8L Isuzu Turbo Diesel that is emissions-legal.  Gavin was kind enough to document his conversion with the following commentary and illustrations so that other owners may benefit fro his experience.

Finding the Right Vehicle and Engine

New EngineI bought the RR at a local auction yard, the classics are practically extinct here in Manitoba, Canada. I had all but decided to import a nice clean one from the U.S when this ratty specimen popped up local. No one knew what it was so I got it for $3500 Cad. I accepted that the lower cost to buy a "scruffy" unit would offset the tidy up needed.

Once I had the Rangie I started to search all my usual haunts for a "nice" diesel to fit in it. Having done an Isuzu swap while still living in the U.K I naturally wanted to find an Isuzu. A new one in Canada was a staggering $10,850. When I got up off the floor I quietly backed out of the dealers and went in search of something more affordable. All the engines I could find in North America are what I call "clunkers"; slow speed industrials. After a disheartening search I turned to ebay to see what I could find. On the second search I found a brand new Isuzu 2.8l TD in Australia. This was the engine that Isuzu was shipping to replace the disastrous 3L engine. Anyway, this bloke in Australia had one to replace the blown 3L in his trooper but then sold the trooper and got left with the engine hence it was being sold off. It was the exact engine I wanted and I suspected it would sell high going by the prices that they sold for in the Brit conversion kits. The bid was ending late at night so I decided on a final price I could afford factoring in shipping. I put a bid of $2200 USd on it and went to bed. The next morning I was the proud owner of an Isuzu for $1750. I couldn't believe my luck.

Photo at right: The new engine arrives!

The Isuzu 4JB1 is a 2.8L diesel engine rated at 120 Bhp. It is very comparable with the original Range Rover Diesel models. The Isuzu is used in the Isuzu Trooper and the Holden Rodeo so it is quite matched to this size of vehicle. There is a sticker on the rocker cover that states its was built to comply with the (Australian Design Rules) ADR70/00 emmissions standards. It is very clean running.

While the engine was enroute from Oz to Canada I proceeded to remove the gas guzzling lump of Aluminum that Rover calls an engine. I cleared the engine bay completely, did my customary worship to the rust gods by the light of a mig welder and prepped everything I could finishing with a coat of red oxide rust primer.  The engine arrived, despite the best efforts of the Vancouver dock strike. The first few days all I could do was look at it appreciatively, caress it a bit and when the wife wasn't looking, left tongue prints on it. I have never owned a brand spanking new diesel before. It was a thing of beauty. Typical Japanese perfection. It was a complete drop in including alternator, power steering pump, vac pump, engine mounts, wiring harness, everything basically.

Rear end of engineMeasuring Up for Mating the Diesel Engine to the Transmisison
Once I got over the initial excitement I set about the more complex task of actually mating this to my ZF automatic. The initial assessment showed that the thick standard flywheel on the Isuzu would actually be a help because the torque converter is actually quite recessed in the bell housing. The original engine has a spacer to move the flex plate back a couple of inches to meet it. After a series of measurements that determined the original flex plate depth into the housing I believe I came up with the measurement of 1.230" deep. This can shift a bit either way as there is some allowance in the design of the torque converter. This allowed me to make a start on the adapter plate which is the most complex component.

Photo at right: Bare back end of new engine that has to be mated to the RR transmission

Machining the Adapter Plate
I measured the maximum radius of the bell housing an cut a circle of plate from a scrap condenser housing that was laying in the yard. It was 1.375" thick which gave me plenty of room. I set it up in the lathe, faced off one side and bored a hole in the middle that fit the end of the crank on the Isuzu. I then flipped it in the chuck and faced the other side ensuring the faces were parallel and the center hole running true. I faced off the second side down to the finished adapter thickness mentioned above. I then bored half way through the plate to the diameter of the old engines crankshaft end.  I took this very heavy slab of plate to the Isuzu engine from which I had removed the flywheel, dowels and factory adapter plate to leave a flat block end (see photo at right). I established a "horizontal" scribe line for reference across the adapter and wiggled it onto the bare crank end. Once it was securely clamped I started with the dowel holes. I carefully drilled them out near size then reamed the holes to provide and exact fit for a .500" dowel. With the dowels tapped in place I then began the layout scribing of the starter position and holes, the bolt circle and recesses needed to clear bolt heads etc.  When I was happy I had all the detail marked I removed the plate and went to the old engine. This was a little more tricky as all he holes are blind. I removed the dowels and machined two dowels with "center punch" points that protruded a slight amount above the mating surface. The most important fact here is to remember to offer up the same face of the adapter as was marked on the Isuzu, not the blank side or it will be ruined by the "mirror effect". I slid the adapter onto the end of the crank, aligned the horizontal line to the Rover engine and gave it two sharp whacks with a copper mallet over the dowels. This created two nice center punch points which let me carefully drill and ream them in the Milling machine. When I offered the adapter back up to the engine the dowels fit with a light tap from the hammer.

Raw material


Raw material for the adapter

Checking the fit of the placte on the Rover engine

The last stage was to get the bolt pattern from the rover which again is all blind. I decided that supreme accuracy was not needed here so I took the easy way out. I cleaned the mating surface and applied a nice smear of machinists dye around each bolt hole, offered up the adapter and with the dowels engaged I tapped it all over with a copper mallet. When I removed the adapter it had some neat blue circles that I could then carefully center and prick punch. With all the holes marked it was then down to a few hours in the mill drilling clearance holes, threading some holes and recessing the heads of those that would interfere and generally avoiding cocking up the dowel holes that required no further machining. A recess was milled for the Isuzu starter and a cutout in the periphery of the adapter to receive the transmission stay bar nut.

The final job was to chuck the whole plate back in the lathe and bore the center out to clear the Isuzu  flywheel (photo below).


Photo showing the center of the adapter being bored out to final size

I am sure all this is a clear as mud but this is a very complex plate to make. It took me about 16 hours. If someone is mad enough to try it I will happily guide them through in greater detail!

Making a Flex Plate Adapter

The next step in the conversion was fitting the flex plate to a standard clutch flywheel. Having already determined the "depth" that the flex plate must protrude into the bell housing I used a series of depth measurements to determine how much "gap" I had to fill between the face of the flywheel and the back of the flex plate. I failed to note this dimension down as I make most of the parts up in my head as I go along. Basically I machined a recess in the face of the flywheel with a ring of six bolt holes tapped into the flywheel .375 UNC. I then machined a disc of .500" plate to fit the recess machined in the flywheel. In the center of this disc I placed a centering hole that mated to the existing spacer reused from the old rover engine. I machined the Rover spacer to the appropriate thickness and fastened it to the disc using the original 12 mm bolts. I hope that is fairly clear as I cannot find a photo of that currently.

Fitting the New Engine into the Rover

With all this complete it was dangerously close to fitting the engine into the rover. The only stumbling block was needing some 12 x 1.00 allen blots for the Isuzu. Once I had my hands on those it was all systems go. One of the impracticalities of this project was that with a solid flywheel there is no way to bolt the torque converter to the flex plate after the engine is in place. This left me with the crappy option of having to bolt the torque converter to the flex plate and install the complete unit as one. This means an extremely delicate guiding of the torque converter onto the two splines and drive dog of the trans pump without nicking the seal.  It was tricky but not the worst thing I have ever done. I had put a new trans input seal in first to get the best chance of success. The two drive splines entered well but the pump was obviously rotating with the engine as i tried to "wiggle" it in. After a frustrating 40 mins or so the was a sudden soft clunk and everything fell together. I almost passed out with relief when I realized the two dowels had also just slid in without the slightest struggle !! The weird and wonderful center punch dowel scheme had worked perfectly. Once I calmed down a bit I quickly put in a couple of bell housing bolts before the whole lot could slid accidentally apart again. Only time would tell if the seal had survived the ordeal.

Leveling the Engine and Adapting the Engine Mounts

The next session involved leveling the engine in the bay. There is no real high tech method to this.I personally  marked the front cross member where the center of the old crankshaft pulley used to be and then lined the Isuzu pulley up to that. I also made sure that the bonnet would clear which was only just. When I was happy with the location of the engine I set about modifying the original Isuzu mounts to fit the rover chassis. On the passenger side this involved making a .500" thick adapter plate that bolted to the range rover then bolted to the Isuzu mount. The Isuzu mounts where much wider and two bolt as opposed to the Rover single bolt units. On the driver side I had to add a small bracket to widen the rover mount as there was very little free space. Pictures of the two mounts appear below.




Passenger (right hand) side engine mount

Driver (left hand) side engine mount

I had to modify the face angles. The passenger side which was also extended due to the engine offset to one side. You can see the .500 spacer under it. The other side was shortened and face angle altered. Due to the compression of the rubber under weight I also added a .125" shim under it to allow for a tiny missguestimation.

With the mounts complete I let the weight of the engine down and the rover had a new heart. I probably took an hour or two out just fettling and coveting. It was all down to the first start of the engine and see if oil poured from the trans input seal!

Test Drive
Gavin reports that the power is adequate -- since this engine was used in the Isuzu Trooper and Holden Rodeo in Australia it is suitable for comparable sized vehicles. "It won't be setting any land speed records but I have had it past 90mph O.K. It has plenty of power for daily driving and moderate towing. The engine is quite matched to the automatic transmission. Its shifts nicely and smoothly with moderate driving. If you really floor it you will likely have to back off the throttle to let it shift otherwise quite a hard shift can result. Its a joy to drive, its not noisy and very smooth running. My wife drives it without complaint!" You can see a short test drive video of Gavin's diesel Range Rover on youtube at http://www.youtube.com/watch?v=qN4A8tSZrF8

More Information
Still to come: a description of how the new engine was tested and the controls hooked up.

A video link on youtube: http://www.youtube.com/watch?v=qN4A8tSZrF8 This is a short test drive of Gavin's diesel Range Rover. 

Some additional photos can be seen on Gavin's business website at www.celticpower.ca

Anyone wishing to replicate Gavin's feat is welcome to email him for additional help.





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Page revised February 1, 2012