A high-performance version of the 6½ Litre, the Speed Six became the most successful racing Bentley, winning Le Mans in 1929 and 1930 at the hands of Woolf Barnato, Sir Henry ‘Tim’ Birkin and Glen Kidston.The Speed Six was an improved version of the 1926 6½ Litre Bentley. W.O. Bentley believed that the best way to increase power was to increase capacity, as opposed to Tim Birkin’s faith in supercharging. He therefore developed a new, larger engine to succeed the 4½-litre.
The Speed Six chassis was introduced in 1928 as a more sporting version of the 6½ Litre. The engine was modified to liberate more power, with twin SU carburettors, a higher compression ratio and a high-performance camshaft, responsible for an increase to 180 bhp. The Speed Six chassis was available to customers with wheelbases of 138 inches (3,505 mm), 140.5 inches (3,569 mm), and 152.5 inches (3,874 mm), with the short chassis being the most popular. 182 Speed Six models were built between 1928 and 1930.
The racing version of the Speed Six achieved two wins at Le Mans in 1929 and 1930, cementing the Speed Six’s place in Bentley history, with the 1929 victory setting a new benchmark for dominance at the race. Driven by Woolf Barnato and Sir Henry ‘Tim’ Birkin, a Speed Six led from the first lap until the chequered flag, followed by a procession of three other Bentleys. A new lap record of 7:21 had been set by Birkin, taking 46 seconds off the previous best and requiring an average speed of 83 mph, and in covering 2,844 km a distance record was also attained. Such a dominant performance by one manufacturer was not seen again at Le Mans for nearly 30 years.