BMC A Series

BMC A-Series
Overview
Manufacturer	Austin Motor Company British Motor Corporation British Leyland Motor Corporation Rover Group MG Rover Group
Production	1951–2000
Combustion chamber
Configuration	Straight-4
Displacement	803 cc (49.0 cu in) to 1,275 cc (77.8 cu in)
Cylinder block alloy	cast iron
Cylinder head alloy	cast iron
Valvetrain	OHV
Combustion
Fuel system	Carburetor or Rover MEMS
Fuel type	petrol
Cooling system	water-cooled
Output
Power output	28 hp (21 kW; 28 PS) to 94 hp (70 kW; 95 PS)
Torque output	40 lb·ft (54 N·m) to 85 lb·ft (115 N·m)
Chronology
Successor	Rover K-series engine

Austin Motor Company's small straight-4 automobile engine, the A-Series, is one of the most common in the world. Launched in 1951 with the Austin A30, production lasted until 2000 in the Mini. It used a cast-iron block and cylinder head, and a steel crankshaft with 3 main bearings. The camshaft ran in the cylinder block, driven by a single-row chain for most applications, and with tappets sliding in the block, accessible through pressed steel side covers for most applications, and with overhead valves operated through rockers. The cylinder head for the overhead-valve version of the A-Series engine was designed by Harry Weslake – a cylinder head specialist famed for his involvement in SS (Jaguar) engines and several F1 title winning engines. Although a 'clean sheet' design the A-Series owed much to established Austin engine design practise, resembling in general design (including the Weslake head) and overall appearance a scaled-down version of the 1200cc overhead-valve engine first seen in the Austin A40 Devon which would form the basis of the later B-Series engine.

The A-Series design was licensed by Nissan of Japan, along with other Austin designs. Improvements were rapid. Early change was to a fit 5 main bearing crank. Head was modified for first E series by swapping plugs and ports, plugs fitted between pushrods and 8 ports eliminated the Siamesed inlet and exhaust ports. Nissan modified the design into the later Nissan A engine that was launched in 1966 with an aluminium head and wedge combustion chambers. It became the basis for many of their following engines notably the later OHC Nissan E engine, was scaled up into Nissan CA engine and ultimately the DOHC 170bhp CA18DET. All these engines show their lineage by the characteristic un-skirted crankcase block of the BMC A series, the A and E also having the bulge in the sump joint face for the oil pump drive. (Nissan engines with deep crankcase skirts are derived from the Mercedes OHC inline 6 that Nissan also licensed in the 1950's.)

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