The longest-lived engine of all

With the inline six already displacing 4.9 litres (having started life at 3.1 litres), more cylinders were clearly needed. Moreover, this was a time when America had emerged as an important market where V8s were the norm: anything less was considered sub-standard and anything more (V12s or even V16s) viewed with suspicion. Without delaying us with the elaborate concept work and various design proposals, thus a V8 configuration was settled upon. It was called the L410, the ‘L’ in R-R terminology denoting a V8, the ‘410’ referring to the 4.10in bore it would retain for its entire life. A comprehensive and very detailed benchmarking programme of all reputable V8s (mostly American) was conducted and, in best R-R fashion, they were duly improved upon.

Over the years so many have erroneously stated or just assumed the L410 was somehow based upon a pre-existing American design, so it needs to be said now that it was an entirely Rolls-Royce and Bentley engine following the most advanced design principles of the time, and in no way a copy, derivative, evolution, licence manufacture or any other version of another V8. At R-R and Bentley, of course, aero engine standards and experience were used: the new engine’s true inspiration came from rather closer to home – the same factory, in fact. The L410’s porting had been inspired by the Merlin aero engine for which the Crewe plant had been built in the 1930s, as was the aircraft-grade high-silicon light alloy material used for the block, contrasting starkly to the Detroit practice of employing cast iron for its blocks. For stiffness it also was a Y-block (extending below the crankshaft) as opposed to the usual shorter V-block. Many other details were also aero-inspired.

Some also confuse its genesis with that of Rover’s similarly alloy V8, which was indeed designed and first produced by General Motors’ Buick division. When GM deemed it too small for the US market and in any case surplus to requirements when GM rationalised its V8s to just small and big block Chevy motors  Rover shrewdly bought the rights and production facilities of America’s most advanced V8. This gave Rover a modern, perfectly good V8 for many years.

To complicate matters, the Bentley S-Type and Rolls-Royce Silver Cloud had just been launched with a rather conventional body-on-frame architecture with a front end packaged around a long, slim inline six, its radiator size and exhaust routing also optimised for that engine. Together these restrictions led to the rejection of an emerging and apparently more modern and efficient hemi-head with V-angled valves, and to the adoption of a rather more conventional wedge-shaped combustion chamber with parallel valves and short exhaust ducts. Half a century later, this turned out to be a lucky stroke indeed.

But back in 1959, the L410 was launched in the Bentley S2 and Rolls-Royce Silver Cloud II with a displacement of 6.23 litres, or rather six-and-a-quarter litres – stylised 6¼ – and a new bore spacing of 4.65 inches. (The company never used cubic inches, although many dimensions were imperial such as the bore and stroke.) As ever the power rating was quoted as ‘adequate’ but in reality about 185bhp – some countries being so shockingly bureaucratic they insisted on actual numbers – and about 300lb ft of torque. It was mated to what was then the world’s best automatic transmission: GM’s four-speed with a hydraulic clutch. It was super smooth in drive-off and all shifts, with a short first gear and top speed achieved in fourth. Initially bought in, it was later brought in-house and, of course, improved. Several generations of GM gearboxes followed adding a torque converter and overdrive in due course.

While subject to constant running changes during production, plus bigger modifications at model changes, the actual displacement was only increased once in its lifetime to 6.75 – or rather 6¾ – litres in 1969 for use in the monocoque Bentley T-series and Rolls-Royce Silver Shadow. Further power increases came with the introduction of fuel injection and a single turbo on the Bentley, resulting in ‘adequate, plus 50 per cent’ power.

For a super-luxury car maker building just a few thousand cars each year, the technology required to keep up to date with emissions and fuel consumption regulations was ever more difficult to meet. In the mid-1990s the company’s owner, Vickers PLC (which had acquired the name in 1973 after Rolls-Royce Ltd had gone into liquidation and been broken up – the car business being hived off, the remainder bought by the British government), sought help in an engine deal with BMW, which both parties considered a first step into ownership by BMW of both R-R and Bentley. The new saloons thus were powered by a BMW-produced V12 for the Rolls-Royce Silver Seraph and a smaller, twin-turbo 4.4-litre BMW V8 for Bentley’s new Arnage, retrospectively called the Green Label.

The L410 continued only in the two-door Bentley Azure and Continental T, and its manufacturing was outsourced. The end of the V8, and of engine-making in Crewe, seemed to have come; sad for a factory originally built to produce 12-cylinder motors (the Rolls-Royce Merlin) more than 50 years earlier.

But, and as we know, the epic battle for Rolls and Bentley ended quite differently with BMW getting the right to call a car a Rolls-Royce (good for BMW and Rolls-Royce, as we can now say in retrospect) and the Volkswagen Group getting everything else: Bentley, the Crewe factory, all design rights and a few days later, a fax from BMW cancelling the engine deal…

This suited Volkswagen CEO Ferdinand Piëch just fine, as he had no desire to continue putting BMW engines in Bentleys in any case. But speed was of the essence in replacing it, as it always was for Ferdinand.

A task-force was put in place to put the L410 into the Arnage – and in typical Piëch fashion, not just in the single turbo version retained by the two-door cars, but the development of a more powerful and more responsive twin-turbo. Volkswagen sent some of its top engineering managers to lead the effort: first Ulrich Hackenberg then Hans-Joachim Rothenpieler as Engineering Directors, and Brian Gush for powertrain, chassis and motorsports, plus all the help from the VW Group that Bentley might want – and, it is fair to say, sometimes didn’t want.

Miraculously, the attitude of suppliers towards Bentley also changed, or was changed for them, very much for the better. I recall a meeting in the boardroom at Crewe with an important supplier who had just told us that he wasn’t particularly interested in our business. But while he was on his way back to the car park on the other side of Pyms Lane – a short walk that we could watch in its entirety from the boardroom – he received a call from his CEO, who had just had a call from Volkswagen’s purchasing director. The chap relocked his car, returned to the boardroom and was suddenly very interested in our business indeed…

Bizarrely, the old V8 had for many years been thought to stand no chance of making whatever emissions standard was coming next. But what we found was that its short exhaust ducts (initially introduced to put less heat into the coolant, so as to preserve the original radiator) helped heat the close-coupled catalyst more quickly and also put more energy into the turbos. At the same time, the wedge-shaped combustion chamber gave ample ‘squish’ for good raw emissions. Big thanks to the design team in the 1950s: a little serendipity goes a long way in engine development.

The L410 – now a twin-turbo – came into the Arnage in 1999 as the Red Label. The BMW-powered Green Label was still offered alongside it and despite being a smooth, free-revving, sweet little engine (though hardly tiny at 4.4 litres), its sales collapsed instantly. Buyers only wanted the 6¾.

The original Bentley V8 had won over the hearts and wallets of enthusiast all over the world with its unique ‘tidal wave of torque’ and unstressed performance: supreme, but not overt. Revving no higher than 4500rpm while delivering huge torque from just above idle, it is the defining characteristic of the ‘Big Bentley’.

Although the original plan was to let the 6¾ fade away with the Arnage, we had a different plan. Not only would the Big Bentley V8 live on, its production would return to Crewe alongside the new W12 (a story I will tell another day). Every single engine was finished by one associate, who at the end signed his or her name on a plate on the engine.

By now I was Bentley’s Engineering Director and when hosting the ‘long service dinner’ for employees celebrating their 25^th or 40^th company anniversary, a colleague asked if I would let him open the bonnet of the Arnage I had driven to the event. Naturally I agreed and watched in admiration as he showed his proud wife the plaque on the top of the engine bearing his signature.

Early in 2004 I bought a 1960 Bentley S2 from a businessman in Norfolk. The following week my lovely wife Alexandra (used to and tolerant of my car follies) and I took it from our Crewe home to the Concours d’Elegance in Bergerac, France, together with Phil and Beth Llewellin in a new Arnage, switching cars as we went. The Arnage used 40 per cent less fuel in spite of emitting 99 per cent less exhaust components and having more than twice the power. The S2 got more looks, though, and traveled in perfect comfort and style, too.

And instead of letting the L410 simply fade away, we strengthened it. From the 400bhp Red Label Arnage we developed the 450bhp Arnage R (red-labelled again) and 500bhp Arnage T (black-labelled like the new W12 Continental GTs), which also delivered the magic numbers: 500bhp and 1000Nm of torque. We also gave it the new ZF 6HP transmission replacing the time-honoured, but now somewhat outdated GM four-speed. Strong enough for the torque, with six speeds, lock-up in all gears for mechanical connection and much faster shifting, it fitted the reborn V8 perfectly to ride-out the wave of torque without any undue rubber-band effect. ZF, as the supplier of the transmission, was still nervous about the torque load. We finally agreed that Bentley would cover any warranty claims stemming from torque, while ZF would, as usual, cover those from manufacturing and so on. But we need not have worried: we never had a single torque-related failure in the field.

Encouraged by the Arnage T’s performance in testing (even on the Nürburgring), we tried a limited-slip differential to aid traction out of tight corners and allow controllable powerslides. Then, at the end of the ‘Ring’s Fuchsröhre (a fast and tricky downhill section followed by a brave left-hand kink; Fox Hole in English) at above 140mph, our best driver reported (backed up by our telemetry) that the car’s rear was now breaking away under power – I still admire his heroic save to this day. So we discarded the idea of the LSD and used the ESP’s brake-traction control instead. The L410’s huge torque had simply overwhelmed the traction of both rear tyres simultaneously, whereas before the spinning inner wheel would simply act effectively as an emergency clutch.

The old V8 proved remarkably adept at fending off modern candidates for its replacement. As we had Bugatti (also headed by Bentley CEO Franz-Josef Paefgen) as a sister brand, someone suggested we use Bugatti’s W16 in naturally aspirated form, the quad-turbo being reserved for the Veyron and, in any case, too wide for our engine bay.

We expected blistering performance from a modern, four-valve 8-litre (a piece of Bentley history shining through here as ‘the 8-litre’ had been the final engine WO had designed for Bentley), the project was named ‘BQA’ for Bloody Quick Arnage. Two versions were built, but the problem was no one could feel any big jump in performance, a fact the supported by the measured data. The final showdown was a drag race we did on the main straight of our Ehra-Lessien proving ground. Up to about 130mph the V8 had the lead, the W16 catching up slowly after that. It’s hard to beat a (nearly) 7-litre twin-turbo V8 with an 8-litre naturally aspirated W16, even if the former is really old. Subsequent experiments with a screw-type supercharger on the W16 also were not satisfactory, while the V8 team kept developing its machine, meaning BQA remained an abandoned project and prototype, like those scalded cats of decades prior.

It was doing the same in the market: the only two competitors were the all-new Rolls-Royce Phantom from BMW (assembled at Goodwood) and the Maybach based on the previous W140 S-Class from Daimler, which had been left empty-handed after the Rolls-Royce and Bentley takeover war. Both were technically accomplished super-luxury cars with excellent 12-cylinder engines, yet the Arnage with its unique character, brilliant heritage and craftsmanship did well against them in media tests and especially with customers.

The new Arnage-based Azure convertible (Project Panama) and Brooklands Coupé (Project Havana) kept using the same powertrains but we felt the Brooklands deserved a power increase. Once more Brian Gush’s team had a solution ready: 530bhp and 1050Nm, otherwise known as ’adequate times two’… On a personal note, I still regret not buying the Azure convertible with the Brooklands chassis and powertrain that we used for development, even though I got an £800 speeding fine in it while testing in Scotland.

Around this time was question was asked by the PR department: could the Azure be called the world’s most powerful four-seat convertible? We did a little research and found it could not: that already was our own Continental GTC Speed with 610bhp.

The L410 reached the high point of its development in the Bentley Mulsanne (Project Kimberley). Upgraded by cam-phasing and cylinder deactivation through switching roller-tappets and mated to a new eight(!)-speed automatic from ZF again, now 1100Nm of torque was on tap. It reduced fuel consumption while delivering the tidal wave even better than any of its earlier incarnations. With the Mulsanne’s new chassis including computer-controlled, infinitely variable dampers and air-springs, it also improved traction tremendously even without an LSD. Unfortunately, the Mulsanne never got a convertible or coupé derivative except from third-party coach builders.

Over its 61-year production run, the old V8 had gone through the most remarkable transformation. Its power output had increased from 185 to 530bhp, or by 286 per cent, torque from less than 400Nm to 1100Nm, a three-fold increase, while simultaneously fuel consumption was almost halved and emissions reduced by more than 99 per cent. Theoretically a Mulsanne could idle on the unburned hydrocarbons spewed out by a 1959 Bentley S2, cleaning all its other pollutants in the process. Actually – and non-scientifically – when my teenage nephews visited us in Crewe and I picked them up in the S2, one asked ‘what’s that smell?’ and I could confidently tell them that it was exhaust gas, which neither of them had ever experienced in uncatalysed form.

Production of the Big Bentley V8 ended in June 2020 with around 36,000 units built in 61 years. If it helps to put that into perspective, both Volkswagen and Toyota build more engines in a single day. Those 61 years probably make Bentley’s V8 the engine with the longest production run ever. The closest contender is the Chevrolet small block, designed in the same era by a small team led by Ed Cole, who later deservedly rose to become General Motors CEO. A strikingly elegant, simple and production-optimised design, it entered production in 1955, but was completely changed in the 1990s and early 2000s – though still using the same bore spacing. At more than 100 million made, it probably is the most-produced car engine in the world, ahead of Toyota’s and VW’s four-cylinder families.

Even today, whenever I drive a car with any version of the Crewe V8 I am emotionally touched by its unique character. And I am proud to have been one of its custodians for a number of years in which we kept it up to date and dramatically increased its performance, making that wave of torque ever gentler and greater.

In 2008, I had the honour of giving the Institution of Mechanical Engineers’ ‘prestige lecture’ for the V8’s 50^th anniversary at the same location as had my predecessor Harry Grylls more than 50 years before. We had invited the surviving members of the original design team, their wives and children, plus those who’d been in charge of it over the decades, to Crewe, inaugurating that day the ‘Harry Grylls’ meeting room. Bentley’s company chauffeurs took them to London in cars using the engines they had created half a century before and they had front-row seating in the IMechE’s oak-panelled theatre with some of Britain’s greatest engineers looking down on us from their oil-paintings.

The lecture was entitled ‘The History of Another Dimension’. The 2008 lecture is available from the IMechE’s website here, as is Harry Grylls’ part one from 1963.

For all readers who want to know more about this fascinating engine and the stories and people around it, there is an excellent book by our friend Karl Ludvigsen called ‘Bentley’s Great Eight’. It’s out of print, I’m afraid, but still available from motor book sellers.