The Austin Motor Company A-series is a British small straight-4 automobile engine. 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 three 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 blocks are not interchangeable between versions intended for conventional end-on mounted gearboxes and the 'in-sump' transaxle used on British Motor Corporation/British Leyland front wheel drive models such as the Mini. 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 Formula One-title winning engines. Although a "clean sheet" design, the A-series owed much to established Austin engine design practice, 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.
Engine family list All engines had a cast iron head and block, two valves per cylinder in an OHV configuration and sidedraft SU carburettor. Engines were available in diesel in the BMC tractor.
All A-series engines up until mid-1970 were painted in British Standard (381c) 223 "Middle Bronze Green".Austin Morris (BL) internal documents archives. This does not include overseas production models such as Australian manufacture. "Factory/dealer warranty replacement" units were painted black, these were primarily distributed for the failures common to the "wet crank" primary gear system in early Minis.
+PetrolIDDisplacementYearsBoreStrokeCompressionratioFuel systemHorsepower@rpmTorque@rpmA1951–19567.5:1Single H2 / Zenith 26JS or 26VME4800 24001959–19808.3:15500 29001956–19648.3:14750 25001964–1967-Twin HS26500 35001961–19648.3:16000 36001962–19808.3:1Single HS24750 2700998 cc (60.9 cu in)1964–197164.58 mm (2.543 in)76.2 mm (3.00 in) -Twin HS255 PS (40 kW; 54 hp)5800 57 lb.ft (77 N.m) 30001963–19678.5:1Twin HS26000 45001962–1980Single HS25200 24501962–1968 -Twin HS255 PS (40 kW; 54 hp)550025001971–1980 - - - - -1964–19718.8:1Twin HS2530030001967–1980 -Single HS4530030001968–1974 -Twin HS260003000A+998 cc (60.9 cu in)1980–199264.58 mm (2.543 in)76.2 mm (3.00 in) 9.4:1Single HIF38525030001980–1992 9.75:1Single HIF44560032001983–1990 9.4:1Single HIF44 / Turbo613026501992–1996 10.1:1SPi550030001996–2000 10.1:1MPi550030001992–2000 10.1:1SPi / MPi58003000DieselA947 cc (51.7 cu in)1962–196962.9 mm (2.48 in)76.2 mm (3.00 in)23.6:1Lucas CAV15 PS (11 kW; 15 hp)2500 1750
A versions
803
The original A-series engine displaced just and was used in the A30 and Morris Minor. It had an undersquare bore and stroke. This engine was produced from 1952 to 1956.
Applications: 1952–56 Austin A30, at 4400 rpm and at 2200 rpm 1952–56 Morris Minor Series II, at 4800 rpm and at 2400 rpm
948 1956 saw a displacement increase, to . This was accomplished by increasing the bore to while retaining the original stroke. It was produced until 1964.
+Applications Model Power output Torque Austin A35 at 4,750 rpm at 2,000 rpm Morris Minor 1000 at 4,750 rpm at 2,500 rpm Austin A40 Farina at 4,750 rpm at 2,000 rpm Austin-Healey Sprite at 5,200 rpm at 3,300 rpm Austin A40 Farina MkII at 5,000 rpm at 2,500 rpm Austin-Healey Sprite MkII MG Midget at 5,500 rpm at 3,000 rpm
848
The bore was retained for 1959s Mini version. This displacement was reached by dropping the stroke to . This engine was produced through to 1980 for the Mini, when the 998 A-Plus version supplanted it.
+Applications Model Years Power output Torque Austin Seven/Austin/Morris Mini 1959–69 at 5500 rpm at 2900 rpm Riley Elf/Wolseley Hornet 1961–62 Austin A35 Van 1963–68 Mini Moke 1964–68 Mini 850/City 1969–80 at 5300 rpm
997 The one-off version for the Mini Cooper used a smaller bore and longer stroke. It was produced from 1961 to 1964.
Applications: 1961–1964 Austin/Morris Mini Cooper, at 6000 rpm and at 3600 rpm
998 The Mini also got a version. This was similar to the 948 in that it had the same stroke but the bore was increased slightly to . It was produced from 1962 to 1992. This engine was first introduced into the Mk II versions of the Riley Elf and Wolseley Hornet, before becoming common fitment in the mainstream Minis.
Model Years Power output Torque Riley Elf/Wolseley Hornet 1962–69 at 5250 rpm at 2700 rpm Mini Moke, Australian Mokes. 1966–82 Mini Moke, Portuguese Mokes. 1983–93 Austin/Morris Mini Cooper 1964–69 at 5800 rpm at 3000 rpm Austin/Morris Mini 1967–80 at 5250 rpm at 2700 rpm Mini Clubman 1969–75 Mini (automatic) 1969–80 at 4850 rpm at 2750 rpm
1098 The version was fitted to:
MG Midget Mk1 1098cc, Oct 19621964 MG Midget Mk2 1098cc, 1964–66 Austin A35 Van 1098cc, 1962–68 Austin A40 Farina Mk2, Oct 19621968 Morris Minor, Oct 19621971 Austin/Morris BMC Saloon from 1962 Mini and its derivatives, the 1098cc engine mounted transversely
It was a stroked (to ) version of the 998 previously used in the Riley Elf and Wolseley Hornet. It was produced from 1962 to 1980.
Years Model Power output Torque 1962–66 Austin A35 Van at 5100 rpm at 2500 rpm 1962–67 Austin A40 Farina 1962–71 Morris 1100/Morris Minor 1000 1962–68 MG 1100 at 5500 rpm at 2500 rpm 1962–64 Austin-Healey Sprite MkII at 5500 rpm at 3250 rpm 1962–64 MG Midget 1963–74 Austin 1100 at 5100 rpm at 2500 rpm 1963–67 Vanden Plas Princess 1100 at 5500 rpm at 2500 rpm 1964–66 Austin-Healey Sprite MkIII at 5750 rpm at 3500 rpm 1964–66 MG Midget MkII 1965–68 Riley Kestrel/Wolseley 1100 at 5500 rpm at 2500 rpm 1973–75 Austin Allegro at 5250 rpm at 2450 rpm 1975–80 Austin Allegro at 5250 rpm at 2900 rpm 1968–82 Mini Moke (Australia only) 1969–71 Morris Mini 1100/Morris Mini K (Australia only) 1971–75 Morris Mini Clubman/Leyland Mini (Australia only) 1975–80 Mini Clubman at 5250 rpm at 2700 rpm 1976–80 Mini 1100 Special
1070 The version was another one-off, this time for the Mini Cooper S. It used a new bore size and the stroke from the 848. It was only produced in 1963–1964. Paired with the even rarer version, below, it became that rarest of things: an oversquare A-series engine.
Applications: 1963–1964 Austin/Morris Mini Cooper S, at 6000 rpm and at 4500 rpm
970 The Mini Cooper S next moved on to a version. It had the same bore as the 1071 cc Cooper S but used a shorter stroke. It was produced from 1964 to 1965.
Applications: 1964–1967 Austin/Morris Mini Cooper S, at 6,500 rpm and at 3,500 rpm
1275 The largest A-series engine displaced . It used the bore from the Mini Cooper S versions but the stroke from the plain Mini Cooper. It was produced from 1964 until 1980, when it was replaced by an A-Plus version. The bore size was around the maximum possible in the block, with very little separation between the middle cylinders, which often contributed to head gasket failures.
Years Model Power output Torque 1964–71 Austin/Morris Mini Cooper S at 5800 rpm at 3000 rpm1965-74 Mini Marcos at 5900 rpm1966–70 Austin-Healey Sprite MkIV at 6000 rpm at 3000 rpm1966–74 MG Midget MkIII1967–68 MG 1300/Wolseley 1300 at 5250 rpm at 3000 rpm1967–68 Riley Kestrel 13001967–68 Vanden Plas Princess 13001967–73 Morris 13001967–74 Austin 13001967 MG 1275/Riley 1275 at 3500 rpm1967 Wolseley 12751967 Vanden Plas Princess 12751968–69 Riley Kestrel 1300/Riley 1300 at 6000 rpm at 3000 rpm1968–71 Austin America (automatic) at 5250 rpm at 2500 rpm1968–73 Wolseley 1300 (manual) at 5750 rpm at 3000 rpm1968–73 MG 1300 MkII at 6000 rpm at 3000 rpm1968–74 Vanden Plas Princess 1300 (manual) at 5750 rpm at 3000 rpm1968 MG 1300/Riley Kestrel 13001969–71 Morris 1300GT at 6000 rpm at 3250 rpm1971–82 Mini Moke Californian Australian only.1969–74 Mini 1275GT at 5300 rpm at 2550 rpm1969–74 Austin 1300GT at 6000 rpm at 3250 rpm1971–80 Morris Marina at 5250 rpm at 2500 rpm1971 Austin Sprite at 6000 rpm at 3000 rpm1973–80 Austin Allegro at 5300 rpm at 3000 rpm1974–80 Mini 1275GT at 5300 rpm at 2550 rpm
A-Plus versions
British Leyland was keen to update the old A-series design in the 1970s. However, attempts at replacement, including an aborted early-70s British Leyland 'K engine' (unrelated to the later Rover K series) and an OHC version of the A series, ended in failure. During the development of what was to become the Austin Metro, engineers tested the A series against its more modern rivals and found that it still offered competitive (or even class-leading) fuel economy and torque for its size. While in the 1970s the A series had begun to seem dated against a new generation of high-revving overhead cam engines, by the end of the decade a new emphasis on good economy and high torque outputs at low speeds meant that the A series's inherent design was still well up to market demands.
Given this, and the lack of funds to develop an all-new power unit, it was decided to upgrade the A-series unit at a cost of £30 million. The result was the 'A-Plus' Series of engines. Available in , the A-Plus had stronger engine blocks and cranks, lighter pistons and improved piston rings, Spring loaded tensioner units for the timing chain and other detail changes to increase the service interval of the engine (from ). More modern SU Carburettors and revised manifold designs allowed for small improvements in power without any decrease in torque or fuel economy. Many of the improvements learnt from the Cooper-tuned units were also incorporated, with A-Plus engines having a generally higher standard of metallurgy on all units, where previously only the highest-tuned engines were upgraded in this way. This made the A-Plus engines generally longer-lived than the standard A series, which had a life between major rebuilds of around in normal service. Studies were made into upgrading the engine to use five main crankshaft bearings but the standard three-bearing crank had proven reliable even in high states of tune and at high engine speeds, so it was not deemed worth the extra funding.
The new engines received distinctive 'A+' branding on their rocker covers and the blocks and heads were colour-coded for the different capacities: yellow for and red for engines.
998 Plus The A-Plus version of the motor was produced from 1980 to 1992.
Applications: Years Model Power output Torque 1980–82 Mini 1000/City/HL at 4750 rpm at 2000 rpm 1980–82 Austin Allegro at 5250 rpm at 3000 rpm 1980–90 Austin Metro at 5400 rpm at 2700 rpm 1982–88 Mini HLE/City E/Mayfair at 5000 rpm at 2500 rpm 1981–86 Austin Metro HLE 1988–92 Mini City/Mayfair at 5250 rpm at 2600 rpm
1275 Plus The larger engine was also given the "A-Plus" treatment. This lasted from 1980 to 2000, making it the last of the A-series line.
+Applications Years Model Power output Torque 1980–82 Austin Allegro at 5600 rpm at 3200 rpm 1980–84 Morris Ital at 5300 rpm at 2950 rpm 1980–90 Austin Metro at 5650 rpm at 3100 rpm 1982–89 MG Metro at 6000 rpm at 4000 rpm 1983–85 Austin Maestro HLE at 5500 rpm at 3500 rpm 1983–93 Austin Maestro at 5800 rpm at 3500 rpm 1984–89 Austin Montego at 5600 rpm at 3500 rpm 1989–90 Austin Metro GTa at 6000 rpm at 4000 rpm 1990–91 Mini Cooper at 5500 rpm at 3900 rpm 1990–91 Mini Cooper S at 6000 rpm at 3250 rpm 1991–96 Mini Cooper 1.3i/Cabriolet at 5700 rpm at 3900 rpm 1991–96 Mini Cooper S 1.3i at 5800 rpm at 3000 rpm 1992–96 Mini Sprite/Mayfair at 5000 rpm at 2600 rpm
1275 Turbo