The L410-series Bentley V8 died this year after a near-61-year production run.
On 4 June, the last of 36,000 examples made since 1959 was fitted to a Mulsanne 6.75 Edition, handbuilt (in a process that takes 30 hours) by a small team separate from the main Crewe activity of producing Continental GTs and Bentaygas.
That made it the oldest passenger-car engine design still being used in a current model, its lifespan only exceeded by the now-departed smallblock Chevrolet V8.
The L-series was really a Rolls-Royce engine, a legacy from the days when Bentley was the subordinate badge-engineered sister marque to its double-barrelled brother, for those customers who wanted a slightly less ostentatious car.
In many ways, the introduction of the V8 in the Rolls-Royce Silver Cloud II and the Bentley S2 tended to further cement the idea in the public mind that there was no worthwhile difference between the two marques.
Suddenly 6.2 litres seemed very ‘adequate’ and, as wealthy people began to get over their reticence about being seen behind the wheel of a Rolls, the Bentley name became very much the junior partner as the ’60s moved into the ’70s.
By the end of the decade, Bentley sales had dwindled to a point that caused the Crewe management to consider dropping the make altogether. It was not until the turbocharged versions of the L-series appeared in the 1980s that Bentley reinvented itself as a marque with a truly separate identity.
At that moment, conventional wisdom might have predicted a further five or 10 years of life for this already venerable all-aluminium pushrod unit.
Were it not for customers’ pushback against the use of BMW engines it might have disappeared in the mid-’90s, but new owner Volkswagen recognised the esteem in which it was held by enthusiasts and gave it a two-decade reprieve as the engine of choice for its largest and most expensive ‘traditional’ models.
Rolls-Royce was not new to V8s, even in ’59.
In fact, it had been among the first to build a V8 of any description: its 1905 Legalimit – governed to the 20mph speed limit – was created as a town car to rival the then-new fad for electric vehicles.
With the exception of the V12 Phantom III and straight-eight Phantom IV, however, the firm had remained faithful to big, quiet, heavy straight-six engines for its private-car chassis.
With, proportionally, the largest development team in the British industry, Rolls-Royce could afford to perfect its straight-six over many years rather than take the risk of developing an all-new design before it was ready.
But as early as 1950 Crewe could see that the remaining development potential in its B60 ‘six’ was limited.
With power-sapping additions such as automatic transmission, maintaining performance was going to be a challenge for an engine that could not realistically be extended beyond 4.9 litres if the block’s rigidity was to be maintained and installation problems avoided.
The Aircraft Engine Division did some initial investigations and came up with a plan for a 5.5-litre V8, favouring the layout’s inherently stiff cylinder block and compact dimensions.
Then, in 1953, Rolls-Royce Motor Cars chief engineer Harry Grylls set lead engine designer Jack Phillips the task of coming up with an all-new unit.
He stipulated that it had to give 50% more power, for no increase in weight or loss of refinement, and with a minimal increase in cost while at the same time fitting into the yet-to-be-announced Silver Cloud/S-type engine bay.
Grylls did not inform Phillips about the conclusions that the AED had come to – or specify that the new engine had to be a V8 – but it quickly emerged as the only sensible choice.
Constructed to aircraft-type tolerances in an alloy with a high silicon content, it had oversquare dimensions, a deep Y-shaped block like the Merlin V12 and wet liners, plus a gear-driven camshaft for refinement.
With a hugely strong bottom end, the new unit would take full throttle on the test rig for 500 hours.
This was in no sense a copy of an American design, but it was benchmarked against a variety of Detroit V8s, which would only do 100 hours given the full-throttle treatment in testing.
The plagiarism myth probably has its origins in the fact that Crewe bought in hydraulic-tappet technology from the USA for the early V8s until it had perfected its own set-up.
The bore spacing, porting and firing order were quite unlike any contemporary American V8.
The first ‘widehead’ unit, with hemispherical combustion chambers and solid tappets, ran for 18 months after the design was settled.
It was installed in a prototype Cloud in May 1955, but the bulky head design made it a tight fit even when the steering box was redesigned.
As a result, a narrower version was schemed, with ‘wedge’ heads, in-line valves and the spark plugs on the outside.
This meant removing the front wheels on the Cloud II and III in order to change the plugs, at least until the cylinder-head design was modified for the new Rolls Silver Shadow and Bentley T-series in 1965.
Engine size went up to 6230cc, so for a 27% increase in capacity Crewe had produced a wider but much shorter engine weighing in at 10lb less than the old straight-six.
Many estimated its power, on twin SU HD6 carburettors, at more than 200bhp but the honest (and undisclosed) figure was just 185.
Some 6046 were built in this form for the Cloud II and S2 (plus 832 for the new Phantom V limousine), all of them run in on test rigs at the Pyms Lane factory using domestic town fuel.
One in every 100 built was subjected to a 100-hour full-throttle test.
For the new Silver Shadow/T1, the height was brought down by redesigning various ancillaries and the heads were redesigned with bigger inlet ports and more ‘squish’ in the combustion chambers. Power was now an honest 200bhp.
In 1971, the engine size was increased to 6750cc. Later, 6.9- and 7.2-litre versions were looked at, but these were felt to be politically questionable in the mid-’70s when the likes of Cadillac were bringing down engine sizes to appease environmentalists.
In fact, a smaller, fuel-injected 5.3-litre L-series (the L380) got much closer to being put into production.
To extract more urge for the Corniche and Camargue, a Solex 4A1 carburettor was fitted; but it was only a matter of time before fuel injection would be required to keep power up in the face of emissions regulations that would soon be taking up half the Rolls-Royce Motor Cars Ltd development budget.
Brico injection was tried but, for the last of the North America-bound 1979 Shadow IIs, a Bosch mechanical system was used.
The V8 was carried over unchanged into the Silver Spirit in 1980, still running twin SUs in most territories outside Japan and North America.
Turbocharging, originally mooted for the Camargue, made its debut in the 1982 Mulsanne Turbo, the Bentley flagship for the two-year-old ‘SZ’ range of saloons.
Using a Garrett T04 turbocharger, this model would quickly turn around the firm’s image from that of a maker of sedate carriages for tycoons to the builder of the world’s fastest luxury cars.
Having established that it would be equal to the emissions, servicing and durability requirements of the future, the long-term viability of the already 20-year-old L-series was then signed off and the 1980s would prove to be a period of consolidation.
Massaged and tweaked for gas flow, timing and thermal loadings to run stronger and cleaner, but as sweetly and quietly as ever, the engine was developed by Crewe into one that would be a single installation for all markets, thus rationalising 2500 parts out of the model line-up.
The naturally aspirated version benefited from many of the refinements devised for the turbo and, with fuel injection, was making some 230bhp by the end of the decade.
By that stage it was the Bentleys, not the Rolls-Royces, that were making all the headlines.
Boost pressure on the 320bhp Turbo R had to be turned down if Crewe wanted GM to sign off on the warranty agreements for its gearbox, which the Americans felt might not be equal to the 500lb ft it originally produced.
Now good for 143mph, the Turbo R was the fastest luxury saloon in the world – and probably the best.
By the end of the decade, non-catalysed turbo Bentleys with the latest Bosch management systems were giving 360bhp.
Turbo engines, with onboard diagnostics and individual coil packs for each cylinder, were made available to Rolls-Royce customers in the Flying Spur and the end was in sight for the non-turbo L-series, the last of them being fitted to the short-lived Silver Dawn version of the SZ in 1997.
As much as 408bhp was now quoted for the Continental T with its water-cooled turbo, but a light-pressure version, at 300bhp, was fitted to the niche 1997-’98 Bentley Brooklands S and R, and the 1997-2000 Rolls-Royce Silver Spur.
The decision by parent company Vickers to move engine production from Crewe to Cosworth in Northampton in 1996 looked like the endgame for the L-series, which by that stage was only used in the Continental and the Azure, having been replaced in the latest four-door cars by BMW-sourced V8s and V12s.
Sadly, the Bentley and Rolls-Royce marques were pulled apart by the various intrigues surrounding the Vickers deal.
But whatever you might think about selling off the two most famous names in British motoring to foreign multinationals, one of the happier outcomes was VW’s decision to continue with the old V8 in its most importantly revised form yet for the Arnage R and T, the latter marketed as the fastest four-door car in the world from 2007 with the twin-turbocharged 500bhp incarnation of the L-series, for which it even claimed better fuel consumption.
A 530bhp version of this engine was developed for the 2008-’11 Brooklands coupé, a low-volume flagship model replacing the Continental Rand T.
At the time it had the highest torque value of any production petrol engine yet built for road use.
The final VW-era Mulsannes were available in standard form, with a mere 500bhp, or as the 530bhp Mulsanne Speed.
At the very top of the range is the extended-wheelbase model, a 180mph-plus tycoon’s office on wheels.
None of these are to be confused with the W12 and V8-engined Continental GTs or the new twin-turbo 6-litre W12 Flying Spur that effectively replaces the handbuilt Mulsanne.
In profile, the Mulsanne is as handsome as you could reasonably expect a 21st-century super-luxury saloon to be in a world where such cars are built to impress oligarchs and billionaires rather than the likes of you and me.
It is faultlessly detailed and finished inside, where the customer is encouraged to customise the cabin to his or her taste – or lack of it.
Among the options are scatter cushions, illuminated tread plates and some horrifying marquetry possibilities, should you feel the need to embellish the flawless veneers in your £239,000 limousine with the sort of imagery normally reserved for the menu in a takeaway restaurant.
This near-190mph, aluminium-bodied, eight-speed behemoth looks as if it should weigh more than its 6000lb and certainly makes light of it.
In many ways, the V8 has been developed to a level of refinement and organ rearranging acceleration that buyers of the latest Teslas take for granted.
That anything so large should move so fast seems almost wrong: time and distance are compressed, the aim being to transmit the occupants – suitably entertained by the Wi-Fi and infotainment systems –seamlessly between climate-controlled environments.
It is a superb technical achievement, built for a different world than the one the S2 inhabited in 1959.
In those days, the difference between a £600 family car and a £5000 Bentley was huge; today, even the least-expensive cars are so fast, safe and capable that all the modern supersaloon can do is add size, ostentation, extra refinement and endless gadgets to soothe your progress.
Though dwarfed by the Mulsanne, the suavely elegant S-type has more presence. It is built on a more human scale in context with its surroundings, conveying benevolent nobility rather than brutish arrogance.
Inside, electric windows are its only nod to decadence but it smells wonderful and feels as welcoming as a favourite armchair.
In general terms it is still a quick, quiet car in which long distances can be covered with minimal effort, but to compare this Edwardian locomotive with its 2020 equivalent is neither fair nor particularly relevant.
Let’s just celebrate the resilience of this greatest of all ‘survivor’ engines.
With its neat plastic covers it looks very different today to the 1959 edition, whose shiny black enamelled finishes link it to its six-cylinder predecessor and even the Merlin V12.
I’d be surprised if they have even a single washer in common, but it is the continuity of development that counts.
And consider this: despite a 200% increase in power, the 2020 Mulsanne V8 still has the same bearing surface area specified by Rolls-Royce engineering chief Harry Grylls, while meeting emissions requirements that are 1000 times more stringent than they were in 1959.
Images: Luc Lacey/Jonathan Fleetwood