1968 Mercedes-Benz 280SE 3.5 V8 Coupé W111 Prototype

2019 Alex Tapley - and Drive-My EN/UK

Cruising the Chilterns in what might be the Sixties’ most important Mercedes-Benz. This W111 280SE 3.5 V8 prototype marked the moment when Mercedes-Benz secured true global influence. We drive it, and discover its miraculous escape from Sindelfingen. Words Sam Dawson. Photography Alex Tapley.

Merc V8 prototype driven. Breaking America On the road in the low-key experimental Mercedes-Benz 280SE 3.5 V8 W111 prototype that took the marque to new heights.

There’s a specific combination of almost intangible qualities that make a true luxury car, and when you experience them working in concert, you can’t help but feel a deep sense of inward satisfaction. As I thread this big Mercedes through the lanes of rural Buckinghamshire, relaxing in its vast sofa of a driver’s seat, I’m enjoying all of them in excess.

1968 Mercedes-Benz 280SE 3.5 Coupé W111 Prototype

1968 Mercedes-Benz 280SE 3.5 Coupé W111 Prototype

The interior surrounds me with restrained chrome detailing, glinting in the sunshine, and the kind of intricate timber work you find on elegant bentwood-formed designer chairs wraps itself around the instrument bezels. The V8 engine has a subtle yet formidable presence, too well-mannered to growl or scream, yet clearly with enough power – or, more specifically, low-rpm torque – to feel effortless and brisk but never breathless when called upon for urge.

‘It maintains a sense of comfort and control in situations where most US rivals would go to pieces’

1968 Mercedes-Benz 280SE 3.5 Coupé W111 Prototype

1968 Mercedes-Benz 280SE 3.5 Coupé W111 Prototype

But most crucially, the ride quality strikes a neat balance between supportiveness and softness that delivers both comfort and a sense of imperious control at the same time. Lesser marques with jack-of-all-trades mid-range saloons offering luxury trim levels never get this vital aspect right, and in order to experience it you need something of the calibre of Bentley, Jaguar and Mercedes. It’s a sign of thorough, dedicated engineering rather than a set of plush seats, so it’s odd to think that when this exquisite luxury car was first assembled at Mercedes’ Sindelfingen plant in 1968, it was lacking in some of these essential qualities. It was built as a six-cylinder 280SE, before being plucked by the experimental department for transformation into a global V8 flagship which would establish Mercedes as we know it today.

‘The engine is an experimental example of Mercedes’ M116 V8’

Back in the Sixties, Mercedes’ luxury coupé and cabriolet flagship, the W111 280SE, was warmly received in Europe but was struggling in the crucial American export market. Whereas European customers were well used to a particular recipe for grand tourers like the 280SE as a six-cylinder species designed to wind its way assertively up Alpine passes or bask on the Cannes seafront, American customers saw big Mercs rather differently.

Sixties America was the market (and heyday) of the personal coupé – effectively a stylish two-door luxury saloon exemplified early on by the 1962 Buick Riviera. A cut above muscle cars, yet beneath hand-built upper-class carriages like the Lincoln Continental MkII, this genre of two-doors combined effortless V8 torque and deep-pile comfort with US mass production to bring the luxury car to a big middle-class audience. To buyers weaned on the likes of the Riviera, Oldsmobile Toronado and Cadillac Fleetwood Eldorado, the 280SE, like the 300SE before it, looked like the personal coupé to beat them all. Mass production made it half the price of a Rolls-Royce – but for the $11,800 a 280SE cost, you could almost have two $6574 Eldorados. Despite the expensive snob-appeal the three-pointed star imbued, however, the 280SE really didn’t deliver on the highway.

You’ve got to get yourself into the right mindset to understand the American market at this time. This was the optimistic America sired by NASA and President John F Kennedy, yet to be dragged back to Earth by the 1973 international oil crisis. The future was one of soaring superhighways populated by high-tech streamlined cars with massively powerful V8s rocketing Americans from city to city at increasing, relentless speed. These were cars born of the Motoramas and the travelling ‘Parade of Progress’ of the Fifties. Detroit’s nationwide visions of tomorrow had actually arrived.

But if an American customer full of this space-age optimism got a 280SE up to speed, they’d be disappointed. The 2778cc straight-six needed working hard, delivering a relatively paltry 200lb ft of torque at 4250rpm and running out of puff at 115mph, whereupon the engine, delivering 160bhp at 5500rpm, was making a high-pitched metallic wail – something unflatteringly reported in US car magazines. American Mercedes owners could talk all they liked about stable handling, but when $4408 Buick Rivieras speared by on the interstate, delivering an effortless 445lb ft at a barely-registering 2800rpm en route to 130mph, their claims fell on deaf ears. To add insult to injury, the 2.8-litre straight-six would only deliver 16mpg when heavily worked. Straight-sixes were marketed as economy cars, and buyers typically wanted their mpg at least into the twenties.

Something needed to be done. On September 18, 1968, Herr Schmidt of Versuchsabteilung (the Mercedes factory’s experimental department) issued an order, euphemistically referring to a ‘face-lifting’ plan, to the production line to build this very 111 Coupé. It had a larger than usual engine bay and a reprofiled bonnet to accommodate a bigger powerplant, but was delivered to Schmidt minus its brake servo, pedals, handbrake, power steering system or steering assembly. The car was to be fitted with a new engine, then returned to the factory (hidden inside a covered wagon) for testing.

The project, given the test number 66 110 11 866, was to be evaluated for production. You’ll notice it’s right-hand drive, unusual for a German-built prototype, but there’s a clue in the paperwork pointing to the potential existence of two cars built in parallel – there are two requests for wagon-delivery from Versuchsabteilung to the production department at the end of the build process on Schmidt’s production order. It seems logical that Mercedes would prototype both left- and right-hand drive versions of a car intended for the entire world.

The engine it was modified to accommodate is an experimental example of Mercedes’ 3.5-litre M116 V8. This engine only went into full production in August 1969, but this particular example was built by Versuchsabteilung 11 months earlier, carrying a letter ‘V’ for ‘Versuch’ stamped into its cylinder block.

It was only Mercedes’ second V8, following on from the enormous 6.3 that powered the 600, and it was the one that would truly succeed in the American market, becoming a mainstay of Mercedes’ range for the next 20 years. Its relatively small size – 3499cc in a market of 7.0-litre big-blocks – betrayed its true innovation; the engine in this car is one of the very earliest to be equipped with Bosch Jetronic fuel injection.

Perhaps on account of the complexity of devising eight-cylinder engine management as opposed to four, the Volkswagen Type 3 fastback first took Jetronic to market 12 months earlier, but Mercedes made it work on a much grander scale. Despite its name, the original Bosch Jetronic was an intermediate step between Mercedes’ own pump-based mechanical fuel injection as pioneered on the 300SL of the Fifties, and the fully electronic microprocessor-controlled systems we’d recognise today.

More accurately called analogue fuel injection, Jetronic was controlled by transistors, and used a brass-bellowed vacuum sensor connected to the intake manifold to meter required injection pulse length. Ironically, in aiming it at the American market, Mercedes was bringing ‘electronic’ fuel injection home – analogue fuel injection had actually been invented by Bendix and briefly offered on some AMCs and Chryslers in 1957-1958, before reliability and servicing issues forced the American firm to cut its losses and sell the patents to Bosch. It retrospectively picked up the ‘D-Jetronic’ moniker – D for druck, meaning pressure – to differentiate it from later, truly electronic versions of the system.

As I pull away from a rural crossroads, the advantage of Jetronic is all too evident. Torque is modest when compared to an American V8 of this era – 211lb ft – but it’s the smoothness that distinguishes it. There’s a lovely heavy, damped action to the instrument-blocking column-mounted automatic gearlever, and acceleration is serene and seamlessly even, with only a vague surge marking each upward gearchange, like a high-speed intercity train accelerating away after slowing through a local station. This sense of silken confidence immediately puts me in mind of the twice-the-price Rolls-Royce Silver Shadow, yet there’s something more ambitious about the Mercedes. The sculpture of the dashboard, with its dramatic cowls, flashes and tiers, is more sophisticated than the homely antique-sideboard slab in the Rolls.

Pitch it into a bend and it’s far more impressive too. Rolls-Royces, Bentleys and most American personal coupés of this era will wallow and lurch quite heavily when presented with a tight corner. Looking at the Mercedes, with its heavy-looking bodywork overhangs, big bumpers, tall chromed grille and overt transatlantic appeal, I’m expecting to experience something similar and steel myself for wheel-twirling, tyre-bouncing understeer.

But that doesn’t happen. It remains dead-level, the traditional Mercedes orthopaedic-firmness of the seats echoed in the tautness of the suspension’s springing. Sporty would be the wrong word, but it feels assertive, confident, and dedicated to maintaining a sense of comfort and control in situations where most American rivals would go to pieces. In the context of late Sixties personal coupés, it keeps its head when all around are losing theirs.

A clue to this sense of composure can be found if you poke around this prototype’s undercarriage with a torch. Each corner features a set of redundant mounting brackets for a W109-derived hydraulic air suspension system only usually available on the long-wheelbase 300SEL saloon. For reasons known only to Schmidt – complexity and cost perhaps – it didn’t survive the evaluation process. But the fact it was trialled demonstrates a desire for serene self-levelling. After all, the AMG racing versions of the mighty 300SEL 6.3 used the air suspension system to great effect, the ‘Red Pig’ racer capable of out-cornering Alfa Romeos and Ford Escorts at Spa-Francorchamps despite its near-two-tonne kerb weight. Either way, the calibration of the springing and damping rates and the inclusion of a hydropneumatic compensator spring at the rear of this conventional, but experimental set-up – its parts, too, were stamped ‘V’ – keeps the car more level through S-bends than a contemporary Citroën DS. It also seems slightly more firmly sprung than standard production 280SE 3.5s I’ve driven.

The steering feels slightly heavier than usual too, requiring a firm pair of hands rather than the laid-back fingertip-control you can deploy with a Rolls-Royce or a Cadillac. It’s nothing hostile – the recirculating-ball set-up is suitably smooth enough, but the hydraulic power-assistance exerts more self-centring force than you might expect. But once again, when you’ve got used to it, it all becomes part of the prototype’s commanding character – it’s a way of introducing some steering feel without allowing any harsh feedback to jar its way through the column. It’s comfortable, but unlike its American rivals it’s anything but vague. It’s a system that you can be precise with.

What this prototype is, then, is a meeting of European grand-touring and American personal-coupé themes. Buyers of neither kind of car would have been disappointed by it, especially when the accelerator was buried in the deep-pile carpet. Memories of the 2.8-litre’s tortured shriek would have been long-banished by the sound of the M116 V8. It’s not muscle-car aggressive, but once you climb beyond A-road near-silence it emits a mellow, delightfully unstressed exotic tenor gurgle, pitched somewhere between a Triumph Stag V8 and a Maserati Quattroporte III.

And of course, it succeeded. The production 280SE 3.5 may only have lasted three years, but it made its mark. Almost as many 3.5s were sold as cheaper 2.8s – 3270 to 3797 – but crucially, those V8 sales were concentrated in the US. In 1971, the M116 engine became the mainstay of the new 107-series SL range, then the W116 S-class.

In the Seventies, despite the oil crisis, Mercedes conquered the American market with its powerful-yet-downsized 3.5-litre M116 V8. Just recall the opening scenes of Donnie Brasco, set in 1976, with the mobsters in the bar arguing about the relative merits of their dinosaur Lincolns and Cadillacs. Mike Madsen walks in, announces: ‘Neither. Mercedes.’ And the discussion as to who makes the best luxury sedan is over. By 1976, Mercedes had doubled its US market share since the introduction of the M116. Cadillac’s share peaked in 1973.

And this car? After its evaluation work was completed, with 2000 test-track miles on its odometer, it was left in storage at Sindelfingen for the remainder of W111 production, where it might have remained were it not for a chance conversation between a dental equipment exporter and his uncle.

In 1971 Oliver Gowers, founder of London-based dental equipment importer Panadent, found out (via an uncle of his German exports contact who worked at Sindelfingen) about an unusual right-hand drive V8 sitting idle at the factory. Gowers flew out to Stuttgart to see the car, arranged the sale there and then for DM24,000 (£11,100) – a lot, but almost half the price of a then-new 350SLC – drove it straight home and used it regularly for 36 years. Since undergoing restoration in 2007, the car has been passed between a few collectors including Neil Clifford, CEO of fashion house Kurt Geiger, although it has always remained in regular, if sparing use. And yet, as it collects admiring glances on its way through the Chilterns, I bet few adoring onlookers understand quite how significant this particular car really is. Without the experiment hiding beneath its bonnet that broke Mercedes into the American mass-market, would the company really be the global manufacturing colossus it is today?



TECHNICAL DATA FILE SPECIFICATIONS 1968 Mercedes-Benz 280SE 3.5 Coupé W111 Prototype

Engine 3499cc V8, sohc per bank, Bosch D-Jetronic fuel injection

Max Power 200bhp @ 5800rpm

Max Torque 211lb ft @ 4000rpm

Transmission Four-speed automatic, rear-wheel drive

Steering Recirculating-ball, power-assisted

Suspension Front: independent, double wishbones, coil springs, telescopic dampers, anti-roll bar. Rear: single-joint swing axle, coil springs, hydropneumatic compensator spring, telescopic dampers

Brakes Servo-assisted discs front and rear

Weight 1650kg (3630lb)

Performance Top speed: 127mph; 0-60mph: 9.4sec

Fuel consumption 22mpg

Cost new n/a

Classic Cars Price Guide £47,500-£110,000 (standard production model)


Reprofiled bonnet reflects the enlarged engine bay to enable the 280SE’s six-cylinder engine to be replaced by a V8. Engine is one of the earliest to get Bosch Jetronic fuel injection. Sculpted dashboard adds to the ambience of pure luxury. For a heavy-weight car, it stays remarkably flat through the bends. This car turned the 280SE into a winner in the lucrative US market. V8-equipped W111 foretold an American success story, yet was almost left to perish.



‘Ironically, I already owned a 300SE Coupé that someone had fitted a 3.5-litre V8 to,’ says the 280SE 3.5 prototype’s owner Jayesh Patel.

‘And when I bought that car, I had originally been looking for a genuine 280SE 3.5, so I never really stopped looking for the real thing. Then I found the real thing while browsing at Greenside Classic Cars – but in effect Mercedes did the same thing, taking a six-cylinder car off the line and converting it! It’s great to own a piece of history like this, though.

It’s needed very little work, and it drives superbly – perhaps a little firmer and more responsive than the production cars. I do wonder what the ride would have been like on the experimental air suspension though, especially compared to my Citroën DS.’


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Additional Info
  • Year: 1968
  • Engine: Petrol V8 3.5-litre
  • Power: 200bhp at 5800rpm
  • Torque: 211lb ft at 4000rpm
  • Speed: 127mph
  • 0-60mph: 9.4sec
  • Club:

     {module Mercedes Benz w111}