Engine
Swept volume ---------- 1991cc (122 cu. in.)
Bore --------------------- 65mm (2.559 in.)
Stroke ------------------- 100mm (3.937 in)
Compression ratio ------ 6.5:1, later 6.75:1
Max. power ------------- 74bhp (55.2kW), later 76bhp (56.7kW) at 4500rpm
Max. torque ------------- 95lb-ft (129Nm) at 2500rpm later 105lb-ft (142Nm) at 2750rpm
Block -------------------- Light alloy with wet liners
Cylinder head ----------- Cast iron, cross-flow
Valve gear --------------- Single overhead camshaft, chain driven, inclined valves
Fuel system -------------- 3 SU carburettors with automatic cold-start device. SU electric pump.
Dry weight --------------- 350lbs (159kg)
Transmission
Clutch ----------------- "Borg and Beck" single dry plate
Gearbox -------------- "Moss" 4 speed manual. Synchromesh on 2nd, 3rd and 4th. Ratios: 3.39, 1.98, 1.37, 1.00
Propeller shaft ------- "Hardy Spicer"
Rear axle (early) ----- "Moss" 4.625:1 ratio,
Rear axle (later) ----- "ENV" 4.55:1. Hypoid bevel gears.
Suspension
Front -------------- Beam axle, "Woodhead" leaf-springs, "Woodhead-Monroe" tubular dampers.
Rear (early)------- Fully floating Moss axle. "Woodhead" leaf-springs. "Girling" lever-arm dampers.
Rear (later) ------- Semi-floating ENV axle. "Woodhead" leaf-springs. "Woodhead-Monroe" tubular dampers.
Brakes
Front (early) --------- "Girling" Hydrastatic HSI. 12" (30.48cm) x 1.656" (4.21cm) drums.
Front (later) --------- "Girling" leading shoe HLS from chassis 1240 onwards. 12" (30.48cm) x 1.656" (4.21cm) drums.
Rear (early) -------- "Girling" mechanical non-servo, 12" (30.48cm) x 1.656" (4.21cm) drums.
Rear (later) -------- from chassis 1240 to 1806 drums were 12" (30.48cm) x 1.676" (4.26cm).
Rear(later still) ---- from chassis 1807 onwards "Girling" hydraulic HW, with 12" (30.48cm) x 1.75" (4.45cm) drums.
Chassis
Material ------- Mild steel, mostly 10swg (6swg at rear end).
Design --------- Mostly box section plus tubular cross-members, a central crusiform of channel section. Underslung rear.
Bodywork
Construction ------ Traditional coach-built body bolted to chassis.
Materials --------- Aluminium-alloy panelling (Duralumin alloy 2017 or one of its successors such as alloy 2024), 18swg for body-shell, 16swg for wings. Body frame of ash timber and birch plywood. Inner panels of mild steel and aluminium-alloy.
Radiator cowl of brass. Most brightwork of chrome-plated brass.
Bumpers of chrome-plated spring steel.
Interior
Upholstery --------- Leather over Dunlopillo cushions.
Trim --------------- Fine cloth, leather, polished wood trim and dash,
velvet-pile carpeting.
Steering ------------ Adjustable for reach and height.
Dials/gauges ------ 0-100mph speedometer, ammeter, water temperature, oil pressure, fuel gauge, electric clock.
Dimensions
Length ------------ 15' 4" (467cm)
Width ------------- 5' 7" (170cm)
Height ------------ 5' 1" (155cm)
Wheelbase --------- 9' 9" (297cm)
Front track ------- 4' 7" (140cm)
Rear track -------- 4' 7" (140cm) with Moss axle
4' 8" (142cm) with ENV axle
Ground clearance --- 7" (18cm)
Frontal area ------ 24 sq. ft. (2.23 square metres)
Tyres -------------5.50 x 17, later 6.70 x 16
Ground clearance: The figure for 7" is as quoted in road tests and contemporary articles. I measured it to be 7.5" for the front axle, with the lowest area of chassis/body 8.5" clear of the ground. The exhaust silencer (under the driver's seat) should be installed 'flat' to maintain ground clearance.
Other data
Kerb weight (with 5 gallons of fuel) --- 2912lbs / 26cwt / 1321kg
Weight distribution ----------------- 48/52 front/rear
Fuel tank capacity ---------------- 11.5 imperial gallons / 52 litres
sometimes 10.5 gallons / 48 litres
Electrical system ----------------- 12 volt "Lucas"
Tyre pressures -------------------22psi (152kPa)
Tyre pressures might have to be changed if non-standard tyres are installed, such as radials and/or non-standard sizes.
Note that original performance figures are likly to be improved upon today. "Pool" petrol of the 1940s helped to keep compression ratios low. In later years (1960s onwards), engines were often uprated, typically to 90bhp. For engine components to increase power and durability, see the AC Engine Project.
Performance (with 74bhp engine and Moss axle)
0-30mph (0-48km/h) --------------- 5.7 seconds
0-50mph (0-80km/h) -------------- 14.1 seconds
0-60mph (0-97km/h) -------------- 19.9 seconds
30-50mph (48-80km/h) in top gear --- 13.4 seconds
Max. speed -------------------- 80mph (129km/h)
Performance (with 74bhp engine and ENV axle)
0-30mph (0-48km/h) ------------------- 6.9 seconds
0-50mph (0-80km/h) ------------------- 16.0 seconds
0-60mph (0-97km/h) ------------------- 22.6 seconds
30-50mph (48-80km/h) in top gear --- 14.1 seconds
Max. speed ----------------------------- 83mph (134km/h)
Performance (with 76bhp engine and ENV axle)
0-30mph (0-48km/h) -------------------- 6.3 seconds
0-50mph (0-80km/h) -------------------- 14.4 seconds
0-60mph (0-97km/h) -------------------- 21.0 seconds
30-50mph (48-80km/h) in top gear ----- 15.8 seconds
Max. speed ------------------------------- 84mph (135km/h)
Note that 0-60mph (or 0 to anything) is a misleading comparison for car acceleration. A timed distance test is a true "yard-stick". A standing start quarter mile time of 22.0 seconds was recorded for the AC (74bhp engine, Moss axle).