While the 4½ litre Bentley is of the sports class, it is tractable and quiet; in acceleration it fulfils the driver's wishes at once… The engine is like that of the former 3-litre model. There are four cylinders and each has four valves. Thus the seating area is increased by half and the cooling surface is greater, while the hammering effect is reduced by two valves with lighter springs than could be used were the valves single. The camshaft is overhead and is driven vertically with adjustment for the gear-mesh. The lubrication is forced, except to the pistons and gudgeon pins, which are oiled by splash.  Continued...