Retro: 1929 Bentley Speed Six

While automotive brands usually like to carry on about weight-saving technologies and new materials – while adding kilos at each model change – Bentley has always made a virtue of being big and powerful.

Not for nothing did Ettore Bugatti (who wouldn’t recognise ‘his’ two-tonne sports cars these days) once describe a Bentley as le camion plus vite du monde (“the fastest truck in the world”).

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If Bugatti didn’t like French honour being insulted by Bentley’s first three Le Mans wins in 1924, ’27 and ’28, there was worse to come. Those were achieved with four-cylinder models of 3.0 and 4.5 litres. Meanwhile, Walter Owen Bentley was already preparing for his next cargo of Le Mans silverware by introducing, in 1926, his first six-cylinder engine, the ‘6½ Litre’.

The first inline six was in fact 4.5 litres, but the extra capacity came about after WO, personally testing the prototype in France, happened upon the prototype Rolls-Royce Phantom 1, also testing there. An impromptu road race convinced WO of the need for more cubic inches – not least because Bentley had his eye on the market for larger, more formal ‘carriage’ cars.

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By 1928 Bentley was preparing a Speed variant of the 6½ Litre, to replace the now ageing four-cylinder. WO had always made known his preference for more displacement, in opposition to some of his drivers’ supercharging experiments that would produce the unsuccessful four-cylinder 4.5-litre ‘Blower’.

The Speed Six began its racing career in 1929, with driver (and Bentley’s chairman and financier) Woolf Barnato leading home a trio of atmo 4½ Litre four-cylinders to sweep the first four places at Le Mans. A year later, Speed Sixes would claim first and second at Le Mans, while the three 4.5-litre ‘Blower’ cars would not see the finish.

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Barnato naturally had various Speed Sixes as his personal road cars; the most famous being a low-roofed Gurney Nutting coupe, celebrated (erroneously) as the car in which he raced the Calais-Mediterranée Express ‘Blue Train’ in 1930. In fact, that was achieved in a Mulliner-bodied Speed Six saloon.

The 6½ Litre and Speed Six were discontinued in 1930, with 363 of the former and 182 Speed Sixes built. Their replacement, the 8 Litre, would be WO Bentley’s last, brief hurrah.

Send more cubes

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The 6½ Litre or ‘Big Six’ was a 6597cc inline six-cylinder, with an aluminium crankcase and one-piece, cast-iron block and head, featuring twin ignition and four valves per cylinder. The Speed Six gained a higher compression ratio (5.8:1), single inlet ports and twin SU carbs, increasing power to 134kW at 3500rpm.

The long and short of it

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With its racing destiny already clear, the Speed Six was offered on a range of wheelbases, from 3502mm to 3874mm. Suspension was by semi-elliptic springs on a beam front and live rear axle. Steering was by recirculating ball, while four-wheel brakes comprised 400mm finned drums, assisted by a Dewandre servo. Spoked wheels were initially 18s with 6.75 tyres, later cars stepped up to 6.75 x 21s.