02 September 2022
Welcome to the latest trend sweeping through Land Rover land. A growing band of owners are powering-up their Defenders with Mercedes OM606 engines. So what’s it all about? LRM lifts the lid on the Benz Brigade and meets two of its biggest fans…
Lord, won’t you buy me a Mercedes Benz? So sang the tragic blues singer, Janis Joplin, in a song she wrote and recorded three days before her untimely death in 1970. To Joplin, the Merc was a symbol of consumerism, but to a growing number of today's dedicated Defender fans it is a passport to affordable power boost. Or, rather, one particular engine is.
We are talking about the legendary OM606 3.0-litre straight-six diesel, which in turbo-powered form produces 174 bhp and 243 lb-ft of torque. If you’ve ever taken a cab ride in a foreign country you’ll almost certainly have been a passenger in a Mercedes taxi powered by this hugely-popular engine, which was in production from 1993 to 2000.
Today, secondhand, the OM606 unit is plentiful, cheap, simple and bulletproof – good for 300,000 miles or more. It’s like a Tdi on steroids.
Of course, engine conversions are nothing new. Over the years we’ve seen just about every oil-burning lump squeezed into the engine bays of everything from Series Is to Range Rover Classics. Here at LRM, editor Patrick, sales manager Steve and myself all drive Land Rovers with very different power units to what Solihull originally intended. So what’s special about the 606?
To find out, we tracked down two Defender owners who have created the head-turning 606-based conversions you can see on these pages. Meet 32-year-old Sam Townsend (110 overlander) and Ali Carter, 28, (90 off-roader), who kindly agreed to this grilling…
Sam (left) and Ali pose with their 606-powered creations
How did you got the idea of putting Merc 606 engine in your Land Rovers - and why?
Sam: I first saw a 606 conversion at the Billing Show in 2016. Ollie North (who later started the MercRover group on Facebook) had fitted one into his Defender after designing and producing a selection of adaptor plates that allowed the 606 bellhousing to mate to any of the manual Land Rover gearboxes. Then, after seeing a few videos on YouTube of the noise and acceleration combined with the simple mechanical pump set-up, I was pretty hooked on the idea of doing it to my own 2010 Defender 110, as I was having Td5 issues and had lost faith in the lump after fitting a replacement engine and then rebuilding the top end six months later!
Ali: I had the idea at a Redwinches off-road day, when I saw their project at the time. Neil at Redwinches was building an OM606 Ultra 4 truck, which got me interested in the engines. It looked and sounded awesome!
What are the advantages of this engine?
Ali: The 606 is a very reliable and simple engine with mechanical injector pumps. It’s a similar design to Land Rover’s 300Tdi, but with way more power.
Sam: The engine is very basic but incredibly strong. It can be run on an electronic pump if desired, but the most popular se-up for big power is the mechanical pump with bigger elements. The standard size is 6mm, but most opt for the 7.5mm set-up, which is capable of producing 400+ hp with the correct turbo and fuelling.
These engines were readily available a few years back for not a lot of money, but as with anything that becomes popular, the price has now risen. A few years back you could buy a decent donor car for under £500, but now you’d struggle to find a rusted out MoT failure for less than £1000.
Is it a tight squeeze under a Defender bonnet?
Sam: The six-cylinder engine is about 5cm longer than the Td5 it replaced in my 110 and actually comes in lighter at 210kg compared to the Td5’s 230 kg
Ali: The engines are pretty much the same weight as a 300Tdi, just slightly longer with the two extra cylinders.
There no mistaking the big Merc six-pot in the engine bay
You both opted for the turbo version, rather than naturally-aspirated. Why?
Sam: One thing and one thing only: POWER! The NA versions are slow and are weaker internally, while the turbo versions have been tested up to 5.5bar of turbo pressure before the block cracked!
Ali: These engines love boost. There are plenty out there running 3bar without any problems.
How did you two get to know each other?
Ali: Sam and I shared advice and tips on doing the conversations as we were both learning about them as we were doing it. The Mercrovers group on Facebook is great for advice and what’s needed for a conversation.
Sam: Via Instagram. The first time I actually met Ali was to borrow a Quick Spool Valve. I’d never met him before and he was happy to lend me this part (which cost a few hundred quid) with zero hesitation, so that I could make my truck perform a bit better!
Since then we’ve been to meets, been greenlaning, camping and will be going to shows together this year.
To be honest, everyone’s helpful when it comes to asking for help in the community because we all want to see more of these conversions completed.
Sam's 606-powered 110 overlander is great off-road, too
How has the Merc 606 transformed your Land Rovers?
Ali: Top speed is currently unknown as I’ve never had the bottle take my 90 with its big wheels over 100mph! Power-wise, it’s probably around 2.5x a standard Defender. I had planned to have a dyno day last year, but with all the lockdown restrictions it never happened.
It’s really a toy, so I’ve never bothered to keep track of the mpg, but I have measured it on a couple of long journeys and got 25mpg
Sam: My 110 now sounds better, accelerates faster and has about 2.5 times the power it left the factory with, all whilst returning similar mpg (22/23mpg), but the auto box and mud terrain tyres don’t help!
Merc 606 engine looking good in Ali's engine bay
Is this a job anyone can tackle at home?
Ali: Definitely. With the advice available online, anybody could do it.
Sam: If you own a Land Rover you’re pretty handy with the tools anyway and there’s enough off-the-shelf conversion parts.
Sam: Originally mine was a 2004 110 DCPU TD5 XS, which had been converted to automatic by Ashcroft Transmissions. A traffic accident at 18 resulted in the loss of my right leg, so I drive with my left foot and the throttle is on the left (great anti-theft protection). I was very lucky to come across a Double Cab with the auto conversion and the XS spec. I bought it to build an overlander and explore the greenlanes in the UK and Europe
Ali: I knew the previous owner of my Defender for years and have always liked the kingcab. I had a 90 before for years and then sold it to move onto a Range Rover Classic. I missed the 90 for off-roading and the character of it. I heard it was sale and I knew it needed some work and wanted to make it my own. I started the rebuild with a galvanised chassis from Richards Chassis.
Where did you find your engines?
Sam: I bought the original conversion kit from Dan Thomas via Facebook, it included the freshened-up 606 engine, Mercedes 722.6 gearbox, gearbox controller, Holset turbo, 8mm uprated Dieselmeken pump, rebuilt injectors and a rear bowl sump for axle clearance. I also ordered the adaptor plate to convert the back of the gearbox from Mercedes T/Box to LR LT230. Total cost: about £4500. This is where the project stalled as it took 6 months for the adaptor to arrive. In that time
I then became a bit obsessed with 606 stuff and bought a few more engines and an old Mercedes estate with the 606 engine (which is my other choice of transport). The engine that I bought originally isn’t the one that’s in my truck - that’s now in my estate. I actually fitted one I bought from a forum member and mated it up to my Merc box.
Ali: I was recommended to use Dan Thomas at DT Engine Solutions, as he has done OM606 conversations and supplied everything needed – ie engine, gearbox and adapter.
Ali puts his very capable 90 through its off-road paces
Tell us more about your projects. What problems did you face getting it to fit?
Sam: I wanted to retain the Td5 factory mounts in the chassis in case I decided to go back to the factory engine, so I had to make my own engine mounts that bolted up to the original design. The longer gearbox and adaptor plate also changed where the transfer box and gearbox mounts went. I worked out that if I moved the drivetrain mounts back 70mm I would have the clearance I needed and I could still use LR prop shafts (albeit from different models), which meant nothing custom needed to be ordered.
I made my own bracket to hold the Hi/Lo shifter and the other headache was getting a Mercedes shifter to sit in the same place as the LR shifter did and still function, but after some head-scratching and an extra pair of hands to hold all the moving parts, we worked out the ideal shifter throw to match the gearbox throw.
Ali: I had never done anything this involved before, so it was a big learning curve. Originally my 90 had been a 200Tdi, so I mocked up the gearbox position to the transfer box location so I could keep the same propshafts. There was just enough space left between the front of the engine for a Td5 radiator. Custom gearbox mounts allowed for a full three-inch exhaust.
Off-roader's tools of trade
Sam: I used the Merc five-speed automatic box out of a V8 ML55 AMG, The bellhousing was swapped to the OM bolt pattern and it’s controlled with an OfGear Controller. It has a RedWinch adaptor plate and shaft to convert it from Mercedes to Land Rover LT230 bolt and spline pattern.
Ali: I had a 300Tdi auto Defender before and always liked the ZF four-speed auto for off-roading and in a Defender. The gearbox is a Dan Thomas hybrid race transmission. It’s a full HP24 box with hydraulic shift (not electronic shift).
What other mechanical mods did you make?
Sam: The axles are trussed and have HD diff pans welded on; there are locking diffs front and back and 300m Ashcroft shafts and CVs inside. The transfer box is fitted with an ATB centre diff, has 300m shafts, bigger sump and the casing is sleeved.
Ali: For me, it’s quite a long list:
• 7.5mm DPUK mechanical injector pump
• Holset hx35 turbo
• PT Racing manifold
• 3 inch exhaust and rear stack pipe
• Full-width intercooler
• 4 inch snorkel (homemade)
• Td5 aluminium radiator with twin electric fans
• HP24 DT engine gearbox
• Td5 / D3 gearbox shifter
• 30-row gearbox oil cooler
• Front and rear Xcess 4x4 diffs with Ashcroft lockers (4.1 ratio)
• Ashcroft transmission HD CVs + shafts
• ARB twin compressor with air tank
• Terrafirma performance drilled and vented brakes
• Galvanised Richards Chassis
Holes in bonnet allow heat to escape
What was the most difficult part of the job?
Sam: Getting the engine to sit perfectly straight in the bay. I ended up welding an old extension and socket to the front crossmember and putting the pulley bolt into it to hold it in the right position.
Ali: Finding the time to finish it. Starting a project like this was easy, but when it’s all in bits it felt like it would never get finished. Luckily I had some friends to help where needed.
And the most enjoyable?
Sam: Learning how to TIG weld; making the exhaust system and hearing it fire up for the first time through it.
Ali: The first drive after years of work.
How long did it take?
Ali: I started in April 2017 with a full strip down to see what I want to keep and replace. I decided it was best to use a strong galvanised chassis as there would be a lot more power over the standard form. With moving house and starting a business it was hard to find the time to do anything with it for a while. The 90 was on the road around August 2019. I have also been finishing bits ever since!
Sam: I started it in September 2019 and it was MoT’d in June 2020. For about four months I couldn’t work on it due to a back injury, so realistically it took me about six months.
Could I have done it faster? Maybe, but it wouldn’t have been to the standard it has been completed.
Are you happy with the end result?
Sam: Absolutely, each time I fire it up in the morning it puts a smile on my face!
Ali: Very happy. I like that it’s unique and I doubt there is another one like it.
Any plans for future projects?
Sam: There is a newer six-cylinder Mercedes engine called the OM648 which is a 3.2 diesel common rail engine, I’m currently gathering bits to make that swap a reality. I know it goes against the simplicity of the manual pump, but the torque figures are much more suitable for my needs.
Ali: No plans at the moment, although a Defender is never really finished. There are always new and interesting products being released.
What is your advice for anyone thinking of undertaking a similar project?
Sam: Whatever you think it’s going to take in time and money, double it and add a bit more!
Ali: Check out the Mercrovers group on Facebook for really good advice on what you need for a conversation to an OM606.
The best or nothing – that’s the current Mercedes Benz advertising slogan. It’s also the motto of a growing band of Land Rover enthusiasts like Sam and Ali who are fitting Merc 606 diesel engines to their Defenders and creating jaw-droppingly stunning. We love the fact that Sam and Ali both opted for the turbo OM606 engine, but put it to work in two very different vehicles: a Td5 110 overlander and a Tdi 90 off-road warrior truck.
But we particularly appreciate the fact that Sam and Ali typical Land Rover enthusiasts achieved these results at home, and on a budget.
For would-be home mechanics, the biggest advantage is that OM606s are old-school mechanical engines that don’t rely on electronics. It’s also very satisfying to observe that although the real Defender went out of production five years ago, innovation and brilliance is alive and well and keeping our favourite vehicles on the road.
It’s very easy to see why Merc OM606 conversions are the next big thing in the world of old-style Defenders. With ex-Disco 1-sourced Tdi engines becoming scarcer, the OM606 is an obvious replacement. But be prepared to hang on to your hats, because a standard OM606 produces 57 per cent more power than a Tdi (194 bhp vs 111 bhp) and 25 per cent more torque (243 lb-ft vs 195 lb-ft), while still achieving 24 mpg, compared to a typical Tdi’s 28mpg.
This may sound like heresy to Rover V8 petrol aficionados, but the OM606 even beats the legendary 3.5 ex-Buick eight-pot, which can only achieve 113 bhp and 185 lb-ft – and which returns mpg figures in the teens.
There doesn’t seem to be anything not to like about the OM606, but these are early days and time will tell as to the long-term suitability of these conversions. We’re looking forward to hearing about Sam’s tales of global adventures in his 110 and Sam’s exploits on the off-road course, as well as the reports of many fellow Defender owners who are also taking the OM606 route. Rest assured, LRM will keep you informed.
Creating a world explorer
Sam and Ali at play!
Vehicle: Defender 110 with OM606 engine conversion
Owner: Sam Townsend, Buckinghamshire
What were you hoping to create?
A truck that I can take to the most remote parts of the world and only need a few basic tools to keep it running – and at the same time something that can surprise most things at a set of traffic lights. It also has the added bonus of sounding immense!
Suspension, wheels and tyres?
18-inch Bowler Alloys in Anthracite which have 33x12.5x18 with Toyo Open Country MTs wrapped round them.
The suspension is a combination of OME HD springs and Terrafirma Racing remote reservoir shocks and bumpstops, although I will be swapping out the springs to Eibach as the OME’s are too firm.
Tell us more about how you turned your 110 into an overland vehicle . . .
The truck is fitted with a Patriot roof rack, Bunduawn awning and Autohome Hardshell Rooftent. I have a fridge, cooker and fire pit that I take on the trips. It has a split-charge system and will be getting a diesel heater for the colder weekends to keep the other half happy!
One of the first mods I did was the Drew Wright matting in the interior which decreased cabin noise dramatically. Then I added a better sound system, Focal 5.25in woofers in the lower dash and tweeters in the top dash panel, plus a Focal subwoofer under the rear bench seat – for a Defender it’s very impressive.
Heated bucket seats, Alcantara headlining, removable Nardi steering wheel with carbon paddle shift and the Optimill steering lock.
My favourite gadget is the ARB Lynx, which lets me control the lockers, lights and accessories, has in-built GPS speedometer and compass, keeps an eye on battery voltages and if I wanted to fit air suspension could even control that!
Colour scheme and finish…
It’s Coniston Green with satin black arches. It did have colour-coded arches, but they got lost after I fitted Britpart +30mm arches for some wider wheels. When I went to change back once I’d fitted the Bowlers they had disappeared. There is a bulkhead patch which needs repairing so I’ll be getting the arches and Puma bonnet colour-coded at the same time.
Anything you’d like to add?
If you want to see more of the truck and detailed build pics then have a look at my IG page @samt89_ and to see any future projects including the next engine choice, check out the new business page @rushmereengineering!
Off-road toy for grown-ups
Ali's ex-200Tdi 90 now has a Puma dashboard (colour-coded, of course)
Vehicle: Defender 90 with OM606 engine conversion
Owner: Ali Carter, Surrey
Occupation: Plumbing/heating engineer
What were you hoping to create?
It’s mainly a toy but I plan to look after it and try not to damage it off-road. I never planned
to create an extreme off-roader but because
it took so long I had more money to buy
Suspension, wheels and tyres?
2 inch lift, 35X12.5x16 Maxxis Trepador, 16in Challenger imitation beadlocks
Tell us about your twin-winch set-up…
Front: Redwinch Cobra 1; back: Goodwinch TDS. Goodwinch 24v turbo box to both winches
The Redwinch is fast and powerful and well-engineered. The 24v turbo box makes it even more fast and powerful.
What other off-road mods?
Custom full external roll cage, Dixon Fabrication front bumper modified to accept the Redwinch . There’s also a rear winch tray and LED spot lights
• Exmoor Trim Elite sport seats painted to match body colour
• Full Puma bulkhead and dashboard
• 300tdi Discovery clocks
• 300tdi Discovery center console
• Momo steering wheel
• 110 headlining cut to fit a 90 kingcab
• Mud UK window and van sides trim panels
• Electric windows / central locking from later-style doors
• Sony Double din headunit
• Midlands CB radio
Colour scheme and finish…
It was originally a standard blue colour from the factory but I went for Alveston Red to update it with its rebuild.
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