Benz brigade
Welcome to the latest trend sweeping through Land Roverland. 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…
“It’s like a Tdi on steroids” is the verdict of fans of the big Merc 606 diesel engine conversion
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…
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 seup 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.
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.
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! Powerwise, 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!
"Why the turbo version rather than naturally-aspirated? One thing and one thing only: POWER!"
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.
Tell us more about your projects…
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 antitheft 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.
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.
Gearboxes?
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
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.
“I was hoping to create a truck I could drive to remote parts of the world... as well as surprise everyone at the traffic lights!”
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 jawdroppingly 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 offroad 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 eightpot, 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.
"I'm very happy with the end result. It's unique and I doubt if there's another like it ”