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Bentley 4.5 Litre (1927-1931)

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Bentley 4.5 Litre (1927-1931)
Bentley 4 1/2 Litre 1927 four seater open tourer in the style of Vanden. Catalogue illustration of 4 1/2 Litre Bentley Engine 2 seater taken from the 1928 catalogue. An explanation of why production...

... of the 4 1/2 Litre Bentley was started is not easy to find. The 3 litre Bentley sold at a stable level and collected victory after victory on various racing tracks.Beside this stood the 6 1/2 Litre, a model that fulfilled a highly demanding client's expectations as regards performance and smoothness. At first the newcomer might be judged as in-house competition to established products.

Some insight into the thinking what precipitated launching a new model may be had from its first public appearance. A prototype 4 1/2 Litre Bentley completed the company's team at the 24hr race at Le Mans in 1927, in support of two 3 litres. Quite a lot can be said for the idea that the creation of the 4 1/2 litre came about because the 3 litre didn't offer promises of further tuning and the 6 1/2 litre couldn't fit the bill as Bentley's premier model on the race track due to the tyre problems. In the first entry at the 24 hr race the prototype of the 4 1/2 litre won approval immediately.

It was tipped favourite to win, but had to retire early due to severe damage in the famous White House accident.Around the end of 1927 series production of the 4 1/2 litre began and the first cars were delivered that year.The new model was manufactured in batches of 25 cars each, odifications being incorporated at the beginning of each series only. These were only minor changes, such as alteration to the radiator or the use of better balanced crankshafts, because the fundamental construction of the 4 1/2 litre was remarkably sound.

It was Woolf Barnato's financial injection into Bentley that gave him a major say in the company affairs and one of the 'Bentley Boys', Tim Birkin, won him over to the idea of of achieving more output from the 4 1/2 litre by fitting a supercharger and W O Bentley's opposition to the idea was overruled. Within less than a year four 4 1/2 Bentley's were fitted with Roots twin-rotor superchargers. A change in the cylinder block, crankshaft, pistons and gudgeon pins, and oil pump took place.

On the testbed an output of some 175 bhp was measured about 45 bhp more than the basic engine. It was clear on the race track, however, after only a short time, that the extra power had been gained only at the expense of reliability. Chiefly this was caused by lubrication and cooling problems which often led to the breakdown of the Blower Bentleys. It became common place to see cars retiring with damaged enginesafter having raced through a few laps in record time.

Sales of the 4 1/2 litre Blower Bentley began in April 1930, at a time when the world economic crisis had reached an ominous state. During the years 1936/7 roughly ten years after 4 1/2 Bentley production had ceased) Rolls-Royce built from remaining spare parts, taken over when Bentley was bought, six further 4 1/2litre's. These included the model's production run amounted to a figure of 665 cars. Of these the Blower Bentley amounted to 55 cars, which figure includes the pre-production models built for racing purposes.

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