What's the Story?
There’s a brief pu of black smoke from the exhaust and the Defender 90 twists as the power comes on strong. Not an unexpected sight, but the noise also being expelled from the exhaust pipe is not the expected low burble of a four-cylinder diesel engine. It’s a more highly pitched, far more exciting noise – the sound of extra cylinders adding to the symphony. The way the Defender accelerates, charging quickly through the ratios of its automatic gearbox, it’s obvious there’s more to this Land Rover than first meets the eye. On its tail is a Discovery which, from the sound of it, is powered by a well-sorted Td5 – but this, too, is far from the way it was when it emerged from the factory.
All is revealed as the bonnets of both the Defender and Discovery are lifted. Sitting between the frame rails are engines bearing the distinctive three-pointed star logo of Mercedes. The conversions are the work of Gary Andrews of Gaz Fab in Southampton, a man probably best known for his work creating awesome tube framed Land Rovers. But he’s also turned out to be a bit of a star when it comes to carrying out engine conversions such as these. So, straight in with the obvious question – I ask Gary what gave him the idea of transplanting a Mercedes diesel engine into a Land Rover?
‘In off-road competition it used to be that you could either have loads of power with a Rover or Chevy V8, which was great but had disadvantages – mostly because petrol motors are easily drowned in wet sections. Or you could have a diesel, which is far more waterproof and has good torque, but can fall down when it comes to bhp.’ He’s warming to his theme now: ‘I was surfing the net, watching some drifting, and spotted an older Mercedes estate car going really very well – big puffs of black smoke as it powered its way through the bends. Anyway, it transpired that this car was running a diesel motor with something like 500bhp on tap!
‘It had the Mercedes 606 six-cylinder unit fitted with a stonking great turbocharger and it was giving huge power and torque. I carried on watching the video for a bit longer and then, all of a sudden, I thought, “How hard would it be to get one of these into a Land Rover?”
Being the sort of up-and-at-it bloke he is, once the moment of inspiration had occurred Gary bought a donor Mercedes and got down to the nitty-gritty of the conversion. Space in the engine bay wasn’t a big problem, so physically getting the Mercedes unit under the bonnet wasn’t a huge issue. New engine mounts had to be created and welded to the chassis, but for a seasoned fabricator like Gary it wasn’t difficult.
The hardest part of figuring out the whole process was devising the mechanics of coupling the engine to the gearbox. This first conversion involved a lot of measuring and pencil-sucking on the way to producing drawings for, and then manufacturing, two bespoke adaptors – one for the bellhousing and another that allows the Mercedes engine to turn the internals of a HP22 Land Rover automatic gearbox. As it turned out, the conversion was difficult to figure out initially but, once these two components had been manufactured, everything slotted together nicely. Better still, the engine was a comfortable fit and looked at home in a Land Rover engine bay. So, with the hard work all done, it was simply a case of turning the key and blasting off in a cloud of black smoke, right?
Well, not quite. Once the motor was in, then came the tricky problem of making it run. These engines have a fuel pump that relies on the original Mercedes ECU to get them up and at it. To even attempt to use one of these pumps would mean a nightmare re-programming job at the very least – not a viable solution. The answer was to go low-tech and get hold of a fuel pump from the previous Mercedes 603 diesel. Because this is a purely mechanical device, essentially it was a case of hooking the pump up to the existing Land Rover systems. There’s the added complication of fitting the 603 pump with bigger elements and tuning it, but what you end up with (should it be desired) is a pump that can flow vast quantities of diesel – so if you wish to go mad and fit a monster turbocharger it can deliver enough fuel to satisfy its demands.
Since his initial brainwave, Gary has successfully transplanted both the Mercedes five-cylinder diesel unit (the 605) and the bigger six-cylinder into Green Oval machines. The Discovery pictured here currently sports a 605 motor, while the Defender enjoys life with a 606.
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The resulting hybrids certainly look the part – raise the bonnet of either of them and, were it not for the Mercedes badge glaring at you from the engine cover, I reckon anybody other than a Land Rover aficionado would be hard pressed to realise that these were anything other than factory-fitted motors. The comfortable way that they sit in the engine bays is the result of Gary’s perfectionist tendencies. Going the extra mile is his natural way of approaching any job: in his world, near enough is not good enough. He’s a man who refuses to cut corners, as he readily admits: ‘I hate rushing jobs – it gives me the hump!’
And the verdict from Jerry Thurston?
Love the conversion – probably liked them both equally. But if I really had to choose one? It’s a hard one: luxurious Discovery with the five-pot unit or the more utilitarian Defender with an extra cylinder. But it has to be the Defender six because more is better. The Disco really is very nice, though. Is there any chance I can have them both… please?
This feature appeared in the May 2016 issue of LRO. Current and Back issues are available to download on digital devices here. Please note, we only hold stocks of the the last three back issues.