25/30

Rolls-Royce 25/30

A development of the 20/25, the engine capacity was increased to 4 ¼ litres and for the first time the Rolls-Royce carburettor was replaced with a proprietary Solex instrument.
The 20/25 was also available for sale in 1936.

Production numbers
1201
Year
1936 - 1938
Engine
6 cylinders, capacity 4257cc. Separate cast iron block and two-piece aluminium crankcase with detachable cast iron 6-plug head, deturbulated from 1937. Overhead pushrod operated valves. 7-bearing crankshaft with vibration damper. Pressure fed lubrication with relief valve feeding rocker shaft and timing gears. Oil capacity 14 pints.
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.
Carburation
Stromberg downdraught carburettor with accelerator pump. Exhaust heated inlet manifold.
Fuel
18 gallon rear tank with double SU electric fuel pumps. Electric gauge. Low fuel warning light.
Transmission
4-speed gearbox in unit with engine. Synchromesh 3rd and 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
Marles cam and roller
Chassis lubrication
‘One-Shot’ centralised lubrication system.