The straight six-cylinder postwar engine, which had been briefly made for the aborted by war Bentley Mark V, replaced conventional overhead valve gear with an F-head configuration of overhead inlet valves and side exhaust valves and reshaped combustion chambers.

There were new main and big-end bearings and a more efficient drive to the timing gear. To this prewar mix Rolls-Royce added chromed bores. Initially, this engine retained the Mark V’s capacity of 4257 cc. increased from 1951 to 4566 cc and in 1955, after the introduction of the (standard wheelbase) Silver Cloud, to 4887 cc for the remaining Silver Wraiths.