1929 Bentley 6½-Liter

The Bentley 6½-Litre was conceived as a touring car capable of competing with Rolls-Royce's New Phantom. In Speed Six guise, it proved admirably suited for competition, proven in 1929 when Woolf Barnato and 'Tim' Birkin's Speed Six won the Le Mans 24 Hour Race ahead of a trio of 4½-Litre Bentleys, and Barnato and Glen Kidston repeated the feat in the following year's Grand Prix d'Endurance at the Sarthe circuit ahead of similarly-mounted Clement/Watney.

Bentley Motors was established by Walter Owen Bentley in 1919 in the North London suburb of Cricklewood, though deliveries did not begin until 1921. The first model was a 3-liter car powered by a four-cylinder, single overhead camshaft engine with four valves per cylinder. Customer requests for larger bodies prompted the need for a larger car, partially addressed in 1923 with the introduction of the Long Standard chassis. The refined six-cylinder 6½-Litre model was introduced in 1926 and remained in production for four years, during which time 544 chassis were completed, 182 of them to Speed Six specification.

The six-cylinder engine had a 100-millimeter bore, a stroke of 140 mm, and a single-piece engine block and cylinder head cast in iron. With a single Smiths 5-jet carburetor, twin ignition magnetos, and a compression ratio of 4.4:1, the engine produced 147 horsepower at 3,400 RPM. While the 3 Liter had used a cone-type clutch, the 6½-Litre was equipped with a dry-plate design that incorporated a clutch brake allowing for faster gear changes. Stopping power was by power-assisted four-wheel finned drums with the front using four leading shoes per drum. Wheelbase sizes ranged from 132 to 152.5-inches with the most popular platform measuring 150 inches.

The Speed Six was equipped with a tuned version of the 6½ Litre with a high-performance camshaft, a compression ratio of 5.3:1, two SU carburetors, and a single-port block. It developed 180 horsepower at 3,500 RPM and wheelbase sizes included a short 138-inch platform which was the most popular, a 140.5-inch, and a long 152.5-inch size. The racing versions rested on a 132-inch wheelbase and their engines had a 6.1:1 compression ratio and delivered 200 horsepower.

The most popular Speed Six was the one driven by Barnato with H. J. Mulliner's saloon coachwork in a race against the Blue Train. Barnato reached his club in London before the train was due at the station at Calais. It was long thought that the car was a Gurney Nutting Sportsman Coupe, however, the coupe was delivered to Barnato in May 1930, over a month after the race took place.

by Daniel Vaughan | Jun 2021