It goes without saying that all vintage Bentley motorcars are exciting. The success of the 3 Litre, the 4.5 and the Speed Six at Le Mans and other international racing events during the 1920’s are part of motor racing folklore, with the louvres and leather belts over the bonnet, all adding to the glamour. Today the cars are still raced and rallied enthusiastically by collectors all over the world, supported by a thriving industry of engineers and parts manufacturers who probably provide more complete and extensive support than that of any other vintage marque.

Apart from the 3 Litre, the 4.5 Litre the 6.5 Litre (with the sports version—the Speed Six) the mighty 8 Litre was also produced. The latter was W.O.’s favourite, but the car that always grabs everybody’s attention is, of course, the supercharged 4.5 Litre, the “blower”, the supercar of its day. The huge blower mounted between the front dumb irons, shouts performance and anybody who drives a blower cannot fail to be impressed with the torque and sheer performance the cars provide.

One of the so called “Bentley Boys” Sir Henry Birkin, Bart. known as Tim Birkin was at the centre of the project to supercharge the 4.5 Litre. Birkin’s inherited wealth allowed him to indulge his passion for racing motorcars, and in 1927 he ordered a 4.5 Litre to full team car specification. He raced the car extensively throughout 1928 with great success at Brooklands, Le Mans, Ards, and at other meetings. But at the German Grand Prix at the Nüburgring Birkin was beaten into 8th place by the supercharged Mercedes and Bugattis.
"We were hopelessly outclassed", he said after the race, and reportedly he refused to race an un-supercharged 4.5 Litre ever again.

It is well known that W.O. Bentley was against the idea of supercharging his designs, preferring to attain more power by adding more litres, hence the Speed Six. Birkin, though was determined to see his ideas come to fruition and with some financial help from Woolf Barnato and Dorothy Paget set about turning his ideas into reality. He commissioned Amherst Villiers, a talented engineer who had set himself up as a consultant to engineering companies interested in incorporating supercharger technology into their designs, to start work on supercharging the Bentley 4.5 Litre. He had already had success supercharging Raymond Mays Brescia Bugatti and a 1922 TT Vauxhall. Much redesign work was required. He proposed a heavier crankshaft, a stiffened crankcase, and many other changes. Things did not go particularly well, the initial design proving somewhat troublesome. Villiers improved the supercharger design and then left the project, leaving Bentley to produce the 50 cars required to enable eligibility to race at Le Mans.

The supercharged 4.5 Litre was not a great success. It was underdeveloped and more time was needed. But by this time Bentley, always short of money, was a victim, like so many others, of the Great Depression, and in 1931 the receivers were called in and the glamorous era of the roaring 20’s was over.

Despite the lack of success on the race track the supercharged 4.5 Litre remains an icon of Britsh motorcar design and to acquire one of the original 50 cars is way beyond the pocket of most enthusiasts. The factory themselves have produced a limited number of replica cars which although very attractive are really only a facsimile of the real thing and cannot be registered for road use in many countries. They also command a huge price.

FB3325 started life as standard 4.5 Litre tourer by Harrison (the coachbuilder who built some of the actual team cars). During a rebuild to the very highest standards it has been converted to full Birkin Le Mans team car supercharged specification. The rebuild incorporated a full split pinned chassis, full flow oil filtration, an uprated rear axle, uprated hard shafts, team car style shock absorbers, an alternator and overdrive. The car is capable of being driven at speed over long distances and is suitable for many international rallies and race events.