Rolls-Royce 20hp

20hp 1922 - 1929

This first small Rolls-Royce car became an instant success and is easily distinguished by the horizontal radiator shutters on all but last few produced. It had a 6 cylinder 3 litre engine with a monobloc cast iron cylinder block and crankcase, and detachable cylinder head. It was better suited to lighter coachwork than the Silver Ghost and later Phantoms.

Production numbers: 2940

Technical Specification

Engine : 6 cylinder monobloc with detachable cast iron head. Capacity 3127cc. Overhead pushrod operated valves. 2-part aluminium crankcase. 7-bearing crankshaft with vibration damper. Pressure fed lubrication with relief valve feeding rocker shaft and timing gears. Oil capacity 10 pints.

Ignition: Coil with standby magneto standard from 1924. Semi-automatic timing advance.

Cooling system: Engine driven pump and fan. Horizontal thermostatic radiator shutters.

Carburation: 2-jet type with starting carburettor and automatic air valve.

Fuel system: Rear mounted 14 gallon tank with Autovac. Direct-acting gauge on tank. 2 gallons reserve from 1928.

Transmission: Gearbox in unit with engine. 3-speed with centre gearchange. 4-speed with right hand gearchange from 1925. Singe dry plate clutch. Open drive propeller shaft.

Suspension: Semi-elliptic leaf springs front and rear. Friction shock dampers, hydraulic from 1926 front, 1928 rear.

Brakes: Initially rear wheel only, internal expanding drum, separate independent shoes for foot and hand brakes. Front wheel brakes from 1925 with mechanical servo motor driven from the gearbox.

Steering: Worm and nut.

Chassis lubrication: Oil gun. Part centralised lubrication system from 1929.

The 20hp chassis series A – E are not clearly defined in the Technical Data published by Rolls-Royce. If you need to find out the chassis series of an early 20hp chassis please let us know.