A Bentley with a P6 - sacrilege or common sense?

Although less common today, after the Second World War it was not unusual for Perkins engines to be used as conversions in all manner of machines –from boats and tractors to passenger cars. In the latter category there were some surprising and unique instances and it is one of these which has recently come to light, thanks to Heritage enthusiast Edward Hinde of the 1104D Platform Team.

A copy of ‘The Motor’ magazine of January 21^st 1948 makes interesting reading today, for both style and content, but is made exceptional for containing a lengthy article on the conversion of a 6.5 litre Bentley to accept a Perkins P6(Vehicle) engine!

It appeared that the owner of the car, Mr Bernard Arthur Foster of Kettering, was concerned about running costs (especially the availability of petrol coupons and the price of petrol!) and was considering selling his magnificent machine but, when threatened with a revolt by his wife, had second thoughts and listened to her suggestion to convert the car to diesel power. Mr Foster was a member of the Bentley Owners Club so recognised the possible ‘purist’ reactions, but he decided to investigate possible power units and in due course selected the Perkins P6 as the best option, taking into account its smooth running and high rotational speed. The 85 BHP rating at 2,600 RPM was seen as sufficient for reasonable performance, especially since the engine was appreciably lighter than the original huge Bentley engine.

A second-hand P6 was located, together with the services of a friend experienced with Perkins-powered trucks. Work started and the P6 was soon located into the chassis, mounted on rubber pads and looking lost in the large under-bonnet space. The coupling of engine to Bentley gearbox caused some head-scratching until an ex-Commer truck gearbox was located. This proved to mate conveniently to the existing gearbox, giving a choice of 24 forward speeds! Other modifications, for instance to provide adequate braking and fuel systems, proved straightforward. A certain amount of tuning (including the elimination of governing at high speeds!) provided a road speed of around 80 MPH.

On the road the seven seat limousine, weighing over two tons unladen, proved to be smooth and quiet in operation –surprising the staff from both ‘The Motor’ and ‘The Oil Engine’ who enjoyed a trip. With fuel economy averaging 27-28 MPG and diesel fuel costing one shilling and 8 ½ pence a gallon (say 8p in today’s currency!) the conversion was agreed ‘most repaying’!

This pragmatic solution to a problem 60 years ago compares interestingly with our current fuel cost crisis. What would Mr Foster have said to £5.50/gallon for diesel?

David Boulton May 2008