The 4 litre was an ill-thought-through last minute attempt at restoring the Bentley company to a good financial state. Introduced in 1931, it used a Ricardo F-head engine (modified by Walter Owen Bentley) of half the capacity in the 8 litre chassis in an attempt to attract economy-minded buyers.
Instead, possibly treacherous owner, Barney Barnato, dropped the company into receivership shortly after it went on sale and by devious manoeuvres archrival Rolls-Royce purchased the business to stop production of the dangerously successful 8 litre Bentley. Bentley and his staff and D. Napier & Son Ltd had expected the business would be bought by Napier.
The conventional straight-6 engine used an 85 mm (3.3 in) bore and 115 mm (4.5 in) stroke for a total of 3.9 L (3915 cc/238 in³) of displacement. It lacked the high power output and technology of the previous Bentley-designed engines.