​Wheelbase

135.5” from 1906 – 1913

143.5” from 1913 – 1923

144” and 150.5” from 1923

 

Weight

Typical kerb weight 2.25 – 2.5 tons.

 

Engine

6-cylinder, bore 4.5”, stroke 4.5”, capacity 7036cc. From 1910 bore 4.5”, stroke 4.75”, capacity 7428cc. Compression ratio 3.5 : 1. Side valve, exposed camshaft followers and valve springs. Exhaust and inlet valves interchangeable. Twin cylinder blocks with non-detachable cylinder heads on a 2–piece aluminium crankcase. Cast iron pistons/later changed to aluminium.  7-bearing crankshaft with vibration damper from 1911. Pressure–fed lubrication by gear-type oil pump.

 

Transmission     

Gearbox. 4 speeds with direct drive top (3 speeds 1909 – 1913). Cone clutch. Open propeller shaft replaced by closed torque tube drive in 1911.

 

Carburation                       

Rolls-Royce design, 2-jet type with automatic air valve. Initially cold start aided by priming cup, from 1921 changed to a starting carburettor.

 

Ignition                

Dual system, each firing 6 plugs. Independent trembler coil and magneto.  Later battery/coil ignition and magneto.

 

Cooling System

Rolls-Royce radiator. Fan and centrifugal pump. Thermostat from 1921.

 

Fuel System      

Initially gravity tank under front seat. Tank moved to rear in 1909 with pump driven from gearbox, and from distributor drive from 1919. Autovac from 1924.

 

Suspension        

Front, semi-elliptic.                                                                                                                                        

Rear, initially platform, replaced by cantilever in 1912. Friction shock absorbers from 1908, then Hartford friction type from 1921.

 

Brakes                 

Initially rear wheel brakes only, internally expanding operated by the handbrake and externally contracting on the propeller shaft operated by the footbrake.  From 1913 the footbrake acted directly on the rear wheels also, and from 1924 front wheel brakes were added, operated by a mechanical servo driven from the gearbox.

 

Steering              

Rolls-Royce design, worm and nut.

 

Tyre Pressures         

Beaded edge wheels (895 x 135 or 935 x 135) 60 to 65 psi.

Straight sided wheels (33 x 5) 55 to 60 psi.

Well based wheels (21 x 7) 35 to 40 psi.

All depending on weight and loading of car.

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Specifications (Technical)

Cylinder Firing Order

1-4-2-6-3-5

 

Valve (Tappet) Clearances

Inlet and exhaust 0.004” (set cold, piston at TDC on firing stroke for each cylinder)

 

Spark Plugs

Champion D23 (or NGK AB-6 Long Reach).

Gap (magneto, intermediate position) 0.020” (battery/coil, position over inlet valve) 0.025”.

 

Contact Points

Magneto points gap, typical 0.015”, Watford magneto 0.020”

Battery/coil ignition points gap, 0.020”.

 

 Capacities

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Engine Oil

8 - 10 pints with 10 pints in side mounted reserve oil tank.

 

Gearbox Oil

6 pints

 

Axle Oil

4.5 pints

 

Cooling System

10 gallons

 

Fuel Tank

16 - 20 gallons

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Performance​

Typical Fuel Consumption     11 to 13 mpg                

Engine Oil Consumption        1 pint per 1,000 miles

Cruising Speed                        45 to 50 mph

Maximum Speed                    60 to 70 mph