The 3 ½ litre was replaced by the 4 ¼ litre in 1936, substantially the same car with detail improvements in addition to the larger engine.
In 1938 the M-series or ‘overdrive’ cars were introduced, essentially a continuation of the 4 ¼ litre but with an overdrive top gear and a rear axle ratio designed to cope with the high-speed roads being built on the Continent.
- Production numbers
- 1241
- Year
- Bentley 4 ¼ Litre 1936 - 1938 and M-Series 1938 - 1939
- Engine
- 6 cylinders, capacity 4257cc. Separate cast iron block and two-piece aluminium crankcase with detachable cast iron 6-plug head. Overhead pushrod operated valves. 7-bearing crankshaft with vibration damper. Pressure fed lubrication with relief valve feeding rocker shaft and timing gears.
- Ignition system
- Coil ignition system with standby coil mounted together. Centrifugal advance with hand override.
- Cooling system
- Engine driven water pump and fan. Thermostatically controlled radiator shutters. 1938 in-line thermostat and radiator shutters fixed in open position.
- Carburation
- Twin SU carburettors with hand operated choke, mounted on water-heated inlet manifold.
Fuel: : 18 gallon rear tank with double SU fuel pumps mounted on firewall. Electric gauge. Low fuel warning lamp. - Transmission
- 4-speed gearbox in unit with engine. Synchromesh 3rd and top. 1938 direct drive 3rd gear, overdrive top. Right hand gearchange. Clutch, Borg and Beck type. Open drive propeller shaft.
- Suspension
- Semi-elliptic leaf springs front and rear. Hydraulic shock dampers equipped with ‘Ride Control’.
- Brakes
- Internal expanding 4 – wheel operation with independent handbrake on the rear wheels. Mechanical brake servo motor driven from the gearbox.
- Steering
- Worm and nut. 1938 Marles cam and roller steering box.
- Chassis lubrication
- Centralised ‘One-Shot’ lubrication system.