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Martin’s smiling, but if you look closely that’s fear in his eyes : credit: © Bob Atkins
This bonkers Series I might look innocent, but it packs a serious 435bhp punch

Bright streaks of sunshine peep in through gaps in the door tops. A faint whiff of EP90 rises from beneath the floor panels, and the elephant hide seat offers little in the way of comfort or support. From under the bonnet, the familiar sound of diesel clatter cuts through the air, reverberating inside the tinny hard top. We’re rolling, and the engine note smooths out to an off-beat thrum. The turbo whistles, the revs climb higher, then a split second later we’re hit by a tidal wave of torque and all hell breaks loose.

Both axles bounce against the salty tarmac as all four tyres scrabble for grip and the engine starts to sing, and the scenery blurs, slows, blurs, slows, then blurs again. ‘‘That’s the only problem with this, it takes longer to actually change gear than it does to rev through and reach the next one!’’ laughs Luke Dale, creator of this utterly unhinged Series I.

Luke Dale’s Land Rover collection also includes a Defender 110, Range Rover Classic and an L663 hybrid

​​​​​​I catch my breath and take in the sights inside the cab. There’s peeling paint, a well-used load area and those low back seats that offer token lap belts. But in the centre of the dash sits a gleaming lump of billet aluminium, with Stack gauges nestled neatly in it, and a touch-pad control interface mounted below. Other than the highly-polished centrepiece, there isn’t much to the untrained eye that hints at this old Land Rover’s dark side.

‘‘I actually built it for the UK Ultimate Callout Challenge’’ Luke explains. ‘‘A bunch of other tuners, engine builders and owners of Land Rovers with engine conversions were planning a day at a dyno, to see who could make the most impressive power and torque figures, and I got an invite. Only trouble was, it was under two months away and I didn’t have anything to take.’’

A brief foray on everyone’s favourite auction site later saw Luke heading off to Kidderminster with an empty trailer, and returning to his York headquarters with the 1957 Series I 88in you see here. ‘‘It had a 3.5-litre V8 from a Range Rover when I got it, but I pulled that out,’’ he smiles. ‘‘It worked out well because it also had the LT95 gearbox from the donor, and everyone says how strong they are, which is ideal for what I had in mind.’’

Luke shows Martin the company’s range of conversion parts for Land Rover applications

Luke owns Diesel Pump UK, a company synonymous with maintaining and tuning Mercedes ‘OM’ diesel engines, as well as selling adaptor kits to fit them into pretty much anything you fancy – including Land Rovers. ‘‘I was obsessed with Range Rover Classics as a kid. My dad had a couple as company cars, then a really early two-door Discovery and a P38 Range Rover. It’s a real affliction. When I got the invite to the dyno day, an old Land Rover seemed like the perfect way to pack what we know about getting more power from the Merc engines into something especially quirky.’’

And quirky it is. The 88in hadn’t led an easy life and had been used hard for trialling throughout the 1990s, and the original panels were wrecked. As a way of improving it, the previous owner replaced them with the beautifully worn tub and wings that now make up the body, and a pair of replacement doors have been blended in to match. As I’m about to find out, the work-hardened exterior and bare cab are a stark contrast from the engineering eye-candy that lurks under the bonnet.

A tight squeeze: 2.5-litre five-pot diesel just fits in the 88in’s engine bay

‘‘That’s an OM605, so a 2.5-litre five-cylinder’’ says Luke. ‘‘It’s been fully stripped and rebuilt with forged con rods, and it’s got pretty much all our tuning parts on. They’re a really tough engine and quite popular for Land Rover conversions now, because with one of our injection pumps they run fully mechanically. No electrics needed. That was a decision I made early on for this Land Rover, because when I collected it, the alternator failed on my tow car and I only just got home. With this one, I wanted it to be as simple as possible – once started the engine doesn’t rely on any electrical power at all.’’

Worked-over injection pump is the key to big power from an OM lump

It’s DPUK’s injection pumps that are largely responsible for the huge increase in power and torque, turning a previously mild-mannered 150bhp car engine into the 435bhp monster that sits between the chassis rails of this Series I. ‘‘The injection pump controls the amount of fuel delivered, and the RPM limit of the engine. This one has been built here with the largest elements we sell, 8.5mm, which gives the greatest amount of fuel. I went with those because of what the engine’s been built to do, but it does make the idle less refined,’’ says Luke.

BorgWarner turbo sucks from a special cold air enclosure inside the wing

​​​​​​‘‘To make more power, that fuel needs to be combined with more air, which is done with a billet BorgWarner turbo sucking from a cold air feed under the wing. The engine can also breathe a lot more freely than standard through our billet inlet and exhaust manifolds.’’

Mating the hopped-up Merc engine to the Range Rover four-speed gearbox was done by measuring the bolt patterns of both and taking the depth of the bellhousing, then machining up an adaptor and custom single-mass flywheel. Bespoke mounts were fabricated, and the original front-bowl sump has been binned and replaced with a rear bowl unit from a Jeep 2.7 CRD engine, allowing the front axle to move up and down as intended without hitting anything and causing a big mess.

Fresh paint and billet aluminium parts ‘pop’ against time-worn panels

Engine cooling is taken care of by a huge handmade aluminium radiator, and intake air is kept cold and oxygen-rich by a water-to-air chargecooler with its own electric water pump. ‘‘The radiator for the chargecooler is laid flat under the flap at the front. It looks stealthy, but when I’m driving hard the flap pops up with a vacuum actuator to let more air through,’’ Luke explains. Vacuum is also used to control the LT95’s centre differential lock, and even the engine’s shut-off. Two large aluminium boxes, one under each wing, hold servos for the assisted brakes and clutch – there was no room under the bonnet. Also helping with space-saving are LED headlamps, which Luke admits could look more in keeping with the Series I’s age but were the slimmest he could find to help clear the cooling pack. In line with Luke’s penchant for reliability, all the vehicle’s electrics have been rewired to run relays, switched by the Oxby control panel.

Twin aluminium tanks nestle behind the front wheels, housing brake and clutch servos

With the fitting sorted and the OM605 plied with go-faster bits up and running, Luke set to beefing up the rest of the driveline to deal with the onslaught of the high-revving turbodiesel at full boost – an enormous 3.8 bar, in case you were wondering.

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Running through a Sachs Racing clutch, the standard LT95 unit transfers drive via a pair of heavy-duty propshafts, down to some rather special axles. ‘‘I only had six weeks to get the Series I ready for the dyno day, so Bryan Bush at Design & Development Engineering pulled out all the stops to get the axles done,’’ says Luke. ‘‘They’re the original casings it came on, but they’ve got 300M hardened shafts, uprated front CVs, automatic torque-biasing diffs and disc brakes all-round now.’’

Both axles have been fully rebuilt with upgraded shafts, disc brakes and torque-biasing differentials

At the ends of each axle are tasteful Rostyle steel wheels finished in Limestone, and fitted with 235/70 R16 Cooper Discoverer AT3 tyres which give useful extra width without looking out of place. Supporting the SI’s weight are standard multi-leaf springs on the back and new parabolics on the front, damped by gas dampers. It’s not just the suspension that hasn’t strayed far from original kit; the steering set-up also uses the standard box and relay, which makes the handling interesting with so much grunt on tap.

​​​​​​Talking of power and torque, the plucky Series I ended up winning the dyno day it was built to compete in, with the OM605 chucking out a monumental 435bhp and 414lb ft of torque. Numbers on a screen are one thing, of course. But I want to know how it drives.

 

Behind the wheel

Standard steering is light; pedals need finesse to drive this Series smoothly

Cranking the Mercedes engine into life, it settles into a rhythmic idle. Aside from some chatter from the single-mass flywheel, which disappears when the clutch is dipped, and a slightly choppy note from the worked-over injection pump’s huge fuel delivery elements, everything seems fairly normal.

Clutch down, and into the first of the LT95’s ratios, the first thing that strikes me about the controls is how light everything is. The servo-assisted clutch and brake pedals put a TDCi Defender to shame. The second noticeable trait is how sensitive the throttle pedal is; I find myself bracing my leg against the door to steady it, and driving through the first two gears at tickover. Despite the OM605 being far outside its power band, the Series I’s light weight makes off-boost driving surprisingly flexible.

Out on the open road, I pin the accelerator in third. The revs pick up quickly, but I instinctively ease off as the BorgWarner crams air into the five cylinders and I’m shoved back into the seat. This much power coupled to an old analogue manual gearbox takes some getting used to. A few more light pulls, and I’m still chickening out once full boost comes on. Happily, the disc brakes pull up sharply and predictably and the 88in handles well considering it’s still on leaf springs, but this is truly like nothing else I’ve ever driven before in the power delivery department.

I get a huge sense of relief as I hand Luke the keys back with the Land Rover still in one piece, but part of me wants to drive it more. The feeling of brutal torque and neck-snapping acceleration from something that looks like it’s just been dragged out of a barn is hard to get your head around, but that’s partly what makes this Series I an absolute hoot.

 

Want Merc power in your Land Rover?

The Mercedes OM605 and its bigger six-cylinder brother, the OM606, have proven popular engine upgrades for Land Rovers in recent years (see LRM July 2021 issue) thanks to their toughness, smooth running, ease of tunability and lack of reliance on electronics.

While Luke’s Series I has been built with outright power in mind, the engines can be run in a much milder state of tune (around 300bhp), while still giving a huge boost in power and torque over standard Land Rover powerplants as well as more refinement, behind either manual or automatic gearboxes.

Diesel Pump UK makes all its conversion parts in-house, and everything you need to drop a Merc engine into a Defender, Discovery 1 and 2 or Range Rover Classic is on the shelf and ready to go. There’s even an adaptor to use a six-speed manual Discovery 3 gearbox, among other interesting parts. Check out dieselpumpuk.com for more info.

 

Spec List

Engine and transmission
• 
Mercedes OM605 diesel (five-cylinder 2.5-litre)
• Forged H-beam conrods
• Mechanical injection pump with 8.5mm elements
• Billet inlet manifold
• Billet exhaust manifold
• 3-inch stainless steel exhaust
• BorgWarner turbocharger
• Turbosmart 40mm wastegate
• 3.8 bar boost
• Aluminium radiator
• Chargecooler
• Inner wing cold air feed
• Sachs Racing clutch
• LT95 gearbox

Wheels and suspension
• Servo-assisted brakes and clutch
• Bespoke propshafts
• Design Development Engineering axles
• Disc brakes
• Rostyle steel wheels
• Cooper Discoverer AT3 tyres (235/70 R16)
• Multi-leaf rear springs
• Parabolic front springs
• Gas dampers

Exterior
• Slimline LED headlamps

Interior
• Oxby touchpad and relay controller
• Billet aluminium gauge panel
• Stack tacho and temperature gauges

 

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