Following five years of success with the 3 Litre model, production of the 6 ½ Litre began in 1926. It was originally conceived in 1924 to solve the problems encountered with the Long Standard 3 Litre models performance. The heavier coachwork on the 1 ½ inch longer 3 Litre chassis added weight and in turn made the car sluggish compared to the shorter lighter examples. The new model was originally envisaged to house a 4 ½ Litre engine built along the basic lines of the 3 Litre engine. However, the now infamous encounter between the prototype car and the prototype Rolls-Royce New Phantom in France in 1924 following Le Mans led to the increase in capacity to 6,597cc on all production chassis. The first 6 ½ Litre model was shown at the 1925 Earls Court Motor Show with the first production cars being delivered in early 1926.
The 6 ½ Litre was designed to offer greater power and luxury than its predecessors, continuing the company’s reputation for building large, powerful, fast touring cars. It was aimed at an affluent clientele, many of whom demanded more comfort, performance, and reliability for long-distance travel. The 6 ½ Litre became synonymous with high-end luxury and grand touring.
In 1928 the Speed Six was introduced which quickly became legendary in racing terms. The Speed Six differentiated itself from the standard 6 ½ Litre with green badges as opposed to blue enamel used on the standard 6 ½, a parallel sided radiator, and several detail changes to the engine including the introduction of twin SU carburettors.
It was W.O. Bentleys favourite model and his most successful creation on the racetrack, racking up five wins and four second places in major races between 1929 and 1931. The highlights of these incredibly successful years were victories at Le Mans in 1929 for Barnato and Birkin and again in 1930 for Barnato and Kidston. Incredibly this was Barnato’s third victory in Le Mans in as many years, following his success in 1928 in a 4 ½ Litre.
The changes to the chassis from the 3 Litre to the 6 ½ Litre were significant. Gone was the cone clutch, replaced with a much larger plate clutch. The differential was significantly increased in size and either a BS or C Type gearbox was fitted. The heart of the 6 ½ Litre was its straight six-cylinder engine with overhead camshaft. The engine was an evolution from the earlier 4 ½ Litre model, but it had a larger displacement to provide more power and torque for heavier luxury coachwork. The standard version of the engine produced around 147 horsepower.
In the Speed Six variant, the engine was tuned to produce approximately 180 horsepower, providing the car with much higher performance and making it a competitive force in racing.
The Speed Six also had a shorter wheelbase to improve handling and reduce weight. The car featured a four-speed manual gearbox that was renowned for its robustness, transmitting the substantial power of the straight six engine to the rear wheels. The transmission was designed to handle both the weight of the car and its powerful engine without compromising on smoothness or reliability. The 6 ½ Litre came equipped with finned drum brakes on all four wheels, operated by mechanical linkage. Bentley also incorporated a servo-assisted braking system, to improve stopping power for such a large and heavy vehicle. The car used semi-elliptic leaf springs at both the front and rear axles, providing a balance between comfort and handling. While this setup was relatively simple by modern standards, it was quite effective for the time, offering a smooth ride over long distances. The standard Bentley 6 ½ Litre could reach a top speed of about 90 mph. The Speed Six however could reach speeds of up to 120 mph, which was exceptional for its time, especially considering the size and weight of the vehicle.
The Bentley 6 ½ Litre, especially in its Speed Six variant, was and still is a remarkable motor car. Its technical innovations and racing success earned it a permanent place in automotive history. The car remains an icon of the Bentley brand and pre-war British motoring, celebrated for its engineering excellence and its role in establishing Bentley’s reputation as a maker of both luxury and high-performance vehicles. Its success on the racetracks between 1929 and 1931 cemented the Speed Six’s status as one of the finest racing cars of its era.
Thoughts from Frank Dale
I have been very fortunate to have driven a number of Bentley 6 ½ Litre and Speed Six motor cars over the years, supplying several to collectors around the world. They are magnificent to drive, combining incredible acceleration, beautiful handling and a gearbox that is simply superb. As vintage Bentleys go, if I had to choose just one to own for the rest of my life, it would almost certainly be a Speed Six. I need say no more.