It is three years since we reported on the early stages of the build of Mike Sayers’ 4½-litre Blower Bentley engine, although we have followed its progress with interest. On show at Doncaster, it is now beginning to come together as a recognizable whole. It has now reached the stage of lapping in the valves and fitting the tappets - like many things more difficult on this engine than most others. It is looking quite complete with most of the large pieces of metal now in place.

The blower is Mike’s second Bentley model engine, which follows his much acclaimed first 3-litre, the engine that famously powered the marque’s first winner of the Le Mans 24-hour race. His current project is a 4½-litre ‘Blower’ engine, designed by W.O. Bentley. With the original un-blown 4½, Bentley was looking to produce a more powerful car by increasing the engine displacement. That brought success in three more Le Mans races, 1928-30 in normally aspirated form.

The supercharged version was unveiled at the Olympia Motor Show in 1929. Some 55 examples were built, to comply with Le Mans regulations. W.O. Bentley was not in favour of supercharging his engines, but by then he had lost control of the company to Woolf Barnato, the majority shareholder and chairman. Dorothy Paget financed the Blower project, a change from her great passion of horse racing for which she was famous for many things, including ownership of Golden Miller, the winner of five Cheltenham Gold Cups and a Grand National. She also bred Arkle, regarded by many as the best ever racehorse.

The Blower was essentially a Bentley 4½ with the addition of a Roots-type supercharger made by Amherst Villiers. W.O., still chief engineer at the company, had refused to allow the engine to be modified to incorporate the supercharger. Consequently, it was placed at the end of the crankshaft in front of the radiator, which also made it immediately recognizable. Two carburettors on the intake were protected by a guard. The crankshaft, pistons and lubrication system were unique to the Blower. It produced 175hp at 3500rpm, but in racing form produced 240hp at 4200rpm. Sadly, the company was a victim of the recession and was bought by Rolls-Royce in 1931 for just £125,000.

Mike Sayers’
4½-litre BLOWER