In 1935 the series of large RR cars continued with the introduction of the Phantom III. This new model departed from established Rolls-Royce practice having a superbly-refined and complicated V12 engine and independent coil spring front suspension. The car had outstanding performance.

The engine in effect was two 3 1/2litre cylinder blocks mounted on a common crankcase; however a major departure from previous designs was that the crankcase and cylinder blocks were now integral, being made in aluminium with separate cast iron wet liners. Similarities in design can be seen when comparing the Phantom 3 engine with its larger aero-engine cousins.

Production numbers
1935 - 1939
60degree V12. Capacity 7340cc. Detachable cylinder heads, 24 spark plugs. Overhead pushrod operated valves. Single camshaft. Hydraulic tappets (solid from 1938). 7-bearing crankshaft, 2 conrods per crankpin, with vibration damper. Pressure-fed lubrication via filter and heat exchanger to 3 relief valves that supplied oil at different pressures to crankshaft bearings, rocker shafts and timing gears. Oil capacity 22 pints.
Dual coil, two distributors with twin contact breakers in each. Centrifugally governed timing.
Cooling system
Engine driven pump and fan. Thermostatic controlled radiator shutters.
Down draught, twin choke type with economy jet and accelerator pump.
Fuel system
Dual electric pumps, 33 gallon rear mounted tank, no reserve but warning lamp on dashboard.
4-speed gearbox, separate unit from engine. Synchromesh on 2nd, 3rd and top. From 1938 top was an overdrive ratio. Single dry plate clutch mounted in unit with engine. Open drive propshaft.
Independent coil spring front suspension incorporating adjustable hydraulic dampers. Semi-elliptic rear leaf springs, hydraulic dampers. All dampers automatically adjusted to suit road speed but could be over-ridden by driver.
Internal expanding 4 – wheel operation with independent handbrake on the rear wheels. Mechanical brake servo driven from the gearbox.
Marles cam and roller steering box.
Chassis lubrication
‘One-Shot’ chassis lubrication system.
Jacking system
Integral hydraulic jack on each wheel operated from within the car by a hand pump and lever.