1922 Bentley 3/4½ Litre EXP4

2019 Jonathan Fleetwood and Drive-My EN/UK

Starting at the beginning. What better way to kick off Drive-My’s Bentley Centenary special than with one of its earliest and most significant cars? John Simister tests EXP 4 at Goodwood Circuit. Words by John Simister. Photography Jonathan Fleetwood.

EXP4 – A TRUE VINTAGE ICON Driving one of the earliest Bentleys

Bentley EXP4: on road and track in one of the earliest survivors

It’s all going so well. This rather significant component of vintage Bentley history is steaming along with a vigour not necessarily expected from a 97-year-old car. Crucially, given that history, it is also stopping efficiently. And then the engine goes rough, there are pops and bangs; the motor car is failing to proceed. Have I just ruined its engine, an engine that, unlike that of many a modern-day vintage Bentley, is original? Is it my fault? I’m worried. Generous, arch-enthusiast owner and serial Bentley collector Jonathan Turner has just loaned me his latest acquisition fresh out of recommissioning, and I might have broken it. Don’t know how, but it’s on my watch.

1922 Bentley 3/4½ Litre EXP4

1922 Bentley 3/4½ Litre EXP4

Then it comes back to life. Coughs, clears its throat, resumes the climb from Goodwood up to the South Downs. This is the oldest vintage Bentley I have yet driven (of seven to date) but it’s not dead yet. Maybe it’s the heat. Maybe it’s temperament. Maybe it’s just part of the shakedown process.

The Bentley steams along with a vigour not necessarily expected from a 97-year-old car

It starts misfiring again as we re-enter the Motor Circuit’s environs, but Bentley guru William Medcalf (whose company did that recommissioning) is soon encouragingly relaxed post-investigation after an initial look of dismay. Nothing deeply mechanical, then. Just a petrol peccadillo or an electrical exit. Relieved? You bet.

1922 Bentley 3/4½ Litre EXP4 - driven

1922 Bentley 3/4½ Litre EXP4 – driven

So, that significance. This might look like a typical mid-to-late-1920s Bentley but it’s actually older. It was built in 1922 and is the fourth of Bentley Motors’ ‘experimental’ series, thus bearing chassis number EXP4. The first-ever Bentley, EXP1, was built in 1919, and today’s Bentley company owns EXP2. EXP3, built in 1920, had a closed body. But the company needed another car to act as a test bed for a significant update, which is where EXP4 comes in.

That update was to fit brakes to the front wheels, something car manufacturers up to that time had resisted despite the laws of physics, the effect of weight transfer and so on. Devising a system able to apply force to brake shoes housed within wheels that steer required some ingenuity in those pre-hydraulic days, but Bentley design chief Frank Burgess and his team achieved it. Rods, Perrot shafts and ‘enclosed radiused whiffle-trees’, as described by The Motor in its edition of 18 September 1923 and featuring EXP4, did the job.

That story in The Motor enthused about the system’s smoothness and lack of skidding, and reassured readers wary of the novel phenomenon of a front-wheel skid that the four-wheel braking was set up ultimately to allow the rear wheels to lock first – a situation since discovered to lead to maximum braking instability. The Autocar, a couple of months later, wrote of the method used by ‘Mr FT Burgess’ to measure braking distances and, presumably, to compare them with a two-wheel braking system.

It involved a paint brush loaded with whitewash, mounted on a swinging arm attached to the left-hand leaf spring just ahead of the front axle. As soon as the brake pedal was depressed for the test, it triggered a linkage that swung the arm down and caused the brush to dab the road with whitewash before swinging up again. When EXP4 had stopped, another white mark was made. ‘It was admittedly somewhat crude,’ said WO Bentley himself in The Autocar, ‘but, generally speaking, it proved reasonably satisfactory.’

1922 Bentley 3/4½ Litre EXP4 - driven

1922 Bentley 3/4½ Litre EXP4 – driven

Far from enthusing about the obvious safety benefits of a reduced stopping distance, though, Mr Bentley was ‘strongly of the opinion’ that trying for the shortest possible stopping distance would make the car too dangerous to be ‘put into the hands of the ordinary motoring public’. For that reason, he said, the company had ‘prepared something of a milder nature’. Causing discomfort to passengers under heavy braking was, he implied, a worse outcome than crashing headlong into a solid object. It takes a while for innovations to gain acceptance, it seems…

At this point, EXP was a regular 3 Litre with a tourer body and the original narrow radiator and bonnet. Its brake-testing work complete, and with four-wheel brakes duly specified for Bentley’s production cars, it was adopted by Frank Burgess as his personal car. It continued in its development-hack role, gaining an early example of the new 4½-litre (actually 4398cc) engine and a wider radiator and bonnet to suit, and thus became the first short-chassis (9ft 9.5in wheelbase) 4½ Litre.

Soon after that, by which time Frank had assumed full ownerhip of EXP4, it was rebodied as a saloon. An undated photograph features Frank and his family proudly arrayed by, and on, the Bentley’s ample bulk. Burgess died, tragically prematurely, in 1929. EXP4 next appeared in print in 1933, the year it was bought by 24-year-old Margaret Allan to go racing (with quite some success, as we shall see). It by then sported a tourer body by Park Ward, following a fire in 1931, and looked for all the world like a regular 4½ Litre… unless you looked more closely.

‘We have restored it as it was when Margaret Allan raced it at Brooklands,’ says William Medcalf. ‘The body is the one it raced with, a 3 Litre body with a 4½ Litre bulkhead, so the scuttle is different. The car had been in a collection for over 50 years, untouched. We got it when the collection was sold. Our job was to unpick the pieces and put it back together.’ But how would his craftsmen know what was correct, given EXP4’s history of constant variation and earlier experimentation? ‘We could see it was quirky. Looking at it with the knowledge of later cars, we could see things that seemed wrong. The brake arms and linkages, they were all wrong. But rather than strip out all the “wrong” parts, we tried to work out why they are as they are.

‘Some we can explain, some we can’t. The wing irons, for example, are all in different places. They’re ugly but they’re the real deal, so we bent them straight as needed. Then there’s the handbrake. It’s unique, forged and with a big boss. The little linkages behind the brakes are all hand-made, four of them. The main brake adjuster is the type used on the 6½ Litre.’ William points to holes in the chassis, used for other development ideas then rendered redundant by an advance elsewhere. ‘We stripped EXP4 to its bare chassis so we could 3D-scan it, and it was like a Swiss cheese with all those holes,’ he says. ‘Then there’s the bonnet. Every vintage Bentley bonnet has 12 louvres on each side. This has 13.’

The guided tour of uniquenesses continues. Bonnet catches, headlights, cantilevered headlight mountings, a steel steering column tube: all these differ from regular Bentley fittings. ‘We’ve used the original parts as much as possible,’ says William, ‘including the differential and the engine’s original crankshaft and connecting rods. The engine blew up lots of times when it was being raced, and there’s a plate in the block where a rod went through the side.’ Restoration started two years ago and took a year, culminating in a debut at the Goodwood Festival of Speed and a shakeown run in the Benjafield’s 100. Shortly after my drive, and just before this is being written, EXP4 was bravely driven by William in the Goodwood Revival’s Brooklands Trophy, finishing tenth, up two places from the start. He’d fixed that misfire, then. ‘Yes,’ he told me at the Friday practice session, ‘it was one of the carburettors.’

Margaret Allan came from a wealthy Scottish family who owned the Allan Line Steamship Company. Her mother encouraged her racing exploits, which involved a Lagonda before the Bentley, a three-car MG team in 1934 and other races in other cars. She was the first woman to win a scratch (that is, nonhandicap) race at Brooklands, albeit not in EXP4, and she was the proud recipient of the Brooklands 120mph badge gained for a 1934 fastest lap of 122.37mph in a 6½ Litre Bentley. Only three other women had that badge. Her Brooklands wins in EXP4 came on 8 July 1933 in the Junior Long Handicap (‘Miss M Allan… handled her big Bentley superbly,’ reported The Motor), and on 2 April 1934 in the Ripley Junior Long Handicap. Margaret often finished in the top four if engine trouble didn’t intervene, working EXP4 up to 92mph on the banking and hoping the tyres didn’t get shredded, a perennial Brooklands danger. EXP4’s mudguards, lights, windscreen and hood were removed for racing, but with these reinstated Margaret also entered EXP4 in the Glasgow Scottish Rally and the entertaining-sounding Brighton Beer Trial. Between events the Bentley was her daily driver.

When war came, Margaret put her skills to good use as an ambulance driver, and even became a code-breaker at Bletchley Park. Post war, married to The Motor’s editor, Christopher Jennings, she wrote for Vogue as a motoring correspondent, as well as The Motor and its weekly rival, The Autocar. Her last event with EXP4 was the 1950 Circuit of Ireland Rally: she won the Ladies’ Cup, of course.

Margaret always kept a cushion in her Bentley. It’s still with EXP4 today, a reminder of her interface with the lofty, hefty, heavy machine. Indeed the whole car takes us straight back to early-1930s Brooklands, its look deliciously patinated (Medcalf’s people are experts at reactivating patination where surfaces have had to be restored, and at leaving well alone where they can) and encouragingly grubby around the entrails. EXP4 celebrates its intriguing past and living, burbling presence.

Those mudguards, floating high above the wheels, are undeniably odd, and the union of the 3 Litre body – chopped off aft of the scuttle – with the later, chunkier front end makes EXP4 subty different from every other vintage Bentley. On that scuttle sit only an aero screen and the rear-view mirror. Ahead of it is that bonnet with the extra pair of louvres, under which is a properly period engine complete with brass-bodied ‘sloper’ SU carburettors.

Bang in the middle of the dashboard is an unusual but vital control: the push-pull plunger to pressurise the petrol delivery. Too little pressure and the engine will die, too much and petrol starts to leak or carburettors to flood. Constant vigilance is required on the ‘Bentley Air’ pressure gauge to the plunger’s immediate north-west. And on the extreme left, obscuring the clock (who needs a clock when you’re racing?) is an oil-filler pipe whose cap’s cut-out ‘B’ acts as a crankcase breather. There’s the usual oil filler on the engine, too, but getting to the in-car one is much quicker in the heat of a race. As ever in a vintage Bentley, the handbrake is outside, the gearlever is on the right and the accelerator is between the clutch and brake pedals. So there’s the usual erasure of instincts before manhandling the Bentley out of Goodwood and on to the road. The steering, as expected, is heavy and springy for manoeuvring but surprisingly positive and progressive once you’re rolling. These old Bentleys are a lot more agile than you might imagine, once you’ve learned how to marshal the masses and forces.

The engine, with its four huge cylinders and long stroke, is of course a heaving landslip of torque as it chuffs its deep, hollow burble. Sixteen valves and an overhead camshaft suggest an appetite for revs, but actually it’s spent by 3500rpm and I haven’t dared to go even that far round the giant tachometer. Nor would there be any need; progress is best achieved with a much earlier upshift through the synchromesh-free, sliding-pinion gearbox.

Getting the gearchanges right is one of the greatest challenges when driving a vintage Bentley. This one’s shift is more forgiving than some and I’m soon managing an encouraging number of crunch-free changes. Bounding along the road in such a Bentley, wind blowing, engine singing its bass part to the transmission’s tenor counterpoint, is one of motoring’s great pleasures. Those pioneering brakes seem pretty good, too, all four of them.

But 92mph on the bumpy Brooklands banking, on those tyres? That calls for a bravery I’m not quite sure I possess.

Above, left and below FT Burgess and family with EXP4 in brake-testing guise, circa 1925; Margaret Allan with EXP4 at Brooklands, and at Fingle Bridge Hill, on the 1934 Brighton Beer Trial. Clockwise from far left Simister musters 100bhp from nearly 100 years ago on Goodwood’s start/finish straight; vintage SU ‘sloper’ carbs; Bentley specialist William Medcalf, whose company recommissioned EXP4; plunger handpressurises petrol delivery to those SUs.


1922 Bentley 3/4½ Litre EXP4

Engine 4398cc monobloc four-cylinder, SOHC, 16 valves, two SU ‘sloper’ carburettors

Max Power 100bhp @ 3500rpm

Max Torque 199lb ft @ 1800rpm

Transmission Four-speed non-synchromesh manual, rear-wheel drive

Steering Worm and sector


Front: beam axle, semi-elliptic leaf springs, Hartford friction dampers

Rear: live axle, semi-elliptic leaf springs, Hartford friction dampers

Brakes Mechanical drums

Weight 1600kg approx

0-62mph 9.9sec

Top speed 92mph

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Additional Info
  • Year: 1922
  • Body: Roadster
  • Cd/Cx: 0.55
  • Type: Petrol
  • Engine: 4.4-litre L4
  • Fuelling: SU ‘sloper’ carburettors
  • Aspirate: Natural
  • Power: 100bhp at 3500rpm
  • Torque: 199lb ft at 1800rpm
  • Drive: RWD
  • Trnsms: Manual 4-spd
  • Weight: 1600kg
  • Economy: 18mpg
  • Speed: 92mph
  • 0-60mph: 9.7sec
  • Price: £315,000
  • Type: Petrol