BMC A-Series engine

BMC A-Series
File:BMC A Series 1275cc engine 1996 Mini SPi.jpg
Overview
Manufacturer	Austin Motor Company British 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	gasoline
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)

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. That company quickly began modifying the A-Series as the Nissan A engine, and it became the basis for many of their following engines.

Specifications

BMC A-Series engines

Displacement	Bore	Stroke	Compression ratio	Carburation	Horsepower	@rpm	Torque	@rpm
803 cc	58 mm	76.2 mm	7.5:1	one SU H2 sidedraft	30 PS (22 kW; 30 hp)	5000	46 lb⋅ft (62 N⋅m)	2700
848 cc	62.9 mm	68.26 mm	8.3:1	one SU HS2 sidedraft	33 PS (24 kW; 33 hp)	5500	44 lb⋅ft (60 N⋅m)	2900
948 cc	62.9 mm	76.2 mm	—	one SU HS2 sidedraft	37 PS (27 kW; 36 hp)	4750	50 lb⋅ft (68 N⋅m)	2500
970 cc	70.6 mm	61.91 mm	—	two SU HS2 sidedraft	65 PS (48 kW; 64 hp)	6500	55 lb⋅ft (75 N⋅m)	3500
997 cc	62.43 mm	81.28 mm	—	two SU HS2 sidedraft	55 PS (40 kW; 54 hp)	6000	54 lb⋅ft (73 N⋅m)	3600
998 cc	64.58 mm	76.2 mm	8.3:1	one SU HS2 sidedraft	39 PS (29 kW; 38 hp)	4750	52 lb⋅ft (71 N⋅m)	2700
1071 cc	70.6 mm	68.26 mm	8.5:1	two SU HS2 sidedraft	70 PS (51 kW; 69 hp)	6000	62 lb⋅ft (84 N⋅m)	4500
1098 cc	64.58 mm	83.72 mm	8.5:1	one SU HS2 sidedraft	47 PS (35 kW; 46 hp)	5200	60 lb⋅ft (81 N⋅m)	2450
1275 cc	70.6 mm	81.28 mm	8.8:1	one SU HS4 sidedraft	57 PS (42 kW; 56 hp)	5300	69 lb⋅ft (94 N⋅m)	3000

All engines had a cast iron head and block, and two valves per cylinder in an OHV configuration. 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. : Source Austin Morris (BL) internal documents archives. This does not include overseas production models such as Australian manufacture.

A versions

803

The original A-Series engine displaced just 803 cc and was used in the A30 and Morris Minor. It had an undersquare 58 mm (2.3 in) bore and 76.2 mm (3.00 in) stroke. This engine was produced from 1952–56.

Applications:

• 1952–56 Austin A30, 28 hp (21 kW) at 4400 rpm and 40 lb⋅ft (54 N⋅m) (54 N·m) at 2200 rpm
• 1952–56 Morris Minor Series II, 30 hp (22 kW) at 4800 rpm and 40 lb⋅ft (54 N⋅m) at 2400 rpm

948

1956 saw a displacement increase, to 948 cc. This was accomplished by boring the block out to 62.9 mm (2.48 in) while retaining the original 76.2 mm (3.00 in) stroke. It was produced until 1964.

Applications:

• 1956–62 Austin A35, 34 hp (25 kW) at 4,750 rpm and 50 lb⋅ft (68 N⋅m) at 2,000 rpm
• 1956–62 Morris Minor 1000, 37 hp (28 kW) at 4,750 rpm and 50 lb⋅ft (68 N⋅m) at 2,500 rpm
• 1958–61 Austin A40 Farina, 34 hp (25 kW) at 4,750 rpm and 50 lb⋅ft (68 N⋅m) at 2,000 rpm
• 1958–61 Austin-Healey Sprite, 43 hp (32 kW) at 5,200 rpm and 52 lb⋅ft (71 N⋅m) at 3,300 rpm
• 1961–62 Austin A40 Farina MkII, 37 hp (28 kW) at 5,000 rpm and 50 lb⋅ft (68 N⋅m) at 2,500 rpm
• 1961–64 Austin-Healey Sprite MkII, 46 hp (34 kW) at 5,500 rpm and 53 lb⋅ft (72 N⋅m) at 3,000 rpm
• 1961–64 MG Midget, 46 hp (34 kW) at 5,500 rpm and 53 lb⋅ft (72 N⋅m) at 3,000 rpm

A diesel version of the 948 cc A-Series engine (producing 16 hp (12 kW) at 2,500 rpm and 38 lb⋅ft (52 N⋅m) torque at 1,750 rpm) was produced for the BMC Mini Tractor. It was developed with the help of Ricardo Consulting Engineers. This engine has dry liners. The block is almost identical to the petrol engine. the oil pump has been removed from the camshaft and is driven by an extension to what would have been the distributor drive. A petrol version of this modified engine was 'reverse-engineered' for use in the Mini Tractor whilst retaining parts commonality with the diesel variant, rather than using a standard petrol A-Series unit. The diesel A-Series was also sold as a marine engine under the BMC name alongside the diesel B-Series engines.

848

File:A Series Engine.jpg

An 848 cc A-Series engine in a 1963 Austin Mini

The 62.9 mm (2.48 in) bore was retained for 1959s 848 cc Mini version. This displacement was reached by dropping the stroke to 68.26 mm (2.687 in). This engine was produced through to 1980 for the Mini, when the 998 A-Plus version supplanted it.

Applications:

• 1959–69 Austin Seven/Austin Mini/Morris Mini, 34 hp (25 kW) at 5500 rpm and 44 lb⋅ft (60 N⋅m) at 2900 rpm
• 1961–62 Riley Elf/Wolseley Hornet, 34 hp (25 kW) at 5500 rpm and 44 lb⋅ft (60 N⋅m) at 2900 rpm
• 1963–68 Austin A35 Van, 34 hp (25 kW) at 5500rpm and 44 lb⋅ft (60 N⋅m) at 2900rpm
• 1964–68 Mini Moke, 34 hp (25 kW) at 5500 rpm and 44 lb⋅ft (60 N⋅m) at 2900 rpm
• 1969–80 Mini 850/City, 33 hp (25 kW) at 5300 rpm and 44 lb⋅ft (60 N⋅m) at 2900 rpm

997

The one-off 997 cc version for the Mini Cooper used a smaller 62.43 mm (2.458 in) bore and longer 81.28 mm (3.200 in) stroke. It was produced from 1961–1964.

Applications:

• 1961–1964 Austin/Morris Mini Cooper, 55 hp (41 kW) at 6000 rpm and 54 lb⋅ft (73 N⋅m) at 3600 rpm

998

The Mini also got a 998 cc version. This was similar to the 948 in that it had the same 76.2 mm (3.00 in) stroke but was bored out slightly to 64.58 mm (2.543 in). It was produced from 1962–92.

Applications:

• 1962–69 Riley Elf/Wolseley Hornet, 38 hp (28 kW) at 5250 rpm and 52 lb⋅ft (71 N⋅m) at 2700 rpm
• 1966–82 Mini Moke, Australian Mokes.
• 1983–93 Mini Moke, Portuguese Mokes.
• 1964–69 Austin/Morris Mini Cooper, 55 hp (41 kW) at 5800 rpm and 57 lb⋅ft (77 N⋅m) at 3000 rpm
• 1967–80 Austin/Morris Mini, 38 hp (28 kW) at 5250 rpm and 52 lb⋅ft (71 N⋅m) at 2700 rpm
• 1969–75 Mini Clubman, 38 hp (28 kW) at 5250 rpm and 52 lb⋅ft (71 N⋅m) at 2700 rpm
• 1969–80 Mini (automatic), 41 hp (31 kW) at 4850 rpm and 52 lb⋅ft (71 N⋅m) at 2750 rpm

1098

The 1.1 L (1098 cc) version was produced for the larger BMC saloons. It was a stroked (to 83.72 mm (3.296 in)) version of the 998 previously used in the Riley Elf and Wolseley Hornet. It was produced from 1962–80.

Applications:

• 1962–66 Austin A35 Van, 48 hp (36 kW) at 5100rpm and 60 lb⋅ft (81 N⋅m) at 2500rpm
• 1962–67 Austin A40 Farina, 48 hp (36 kW) at 5100 rpm and 60 lb⋅ft (81 N⋅m) at 2500 rpm
• 1962–71 Morris 1100/Morris Minor 1000, 48 hp (36 kW) at 5100 rpm and 60 lb⋅ft (81 N⋅m) at 2500 rpm
• 1962–68 MG 1100, 55 hp (41 kW) at 5500 rpm and 61 lb⋅ft (83 N⋅m) at 2500 rpm
• 1962–64 Austin-Healey Sprite MkII, 56 hp (42 kW) at 5500 rpm and 62 lb⋅ft (84 N⋅m) at 3250 rpm
• 1962–64 MG Midget, 56 hp (42 kW) at 5500 rpm and 62 lb⋅ft (84 N⋅m) at 3250 rpm
• 1963–74 Austin 1100, 48 hp (36 kW) at 5100 rpm and 60 lb⋅ft (81 N⋅m) at 2500 rpm
• 1963–67 Vanden Plas Princess 1100, 55 hp (41 kW) at 5500 rpm and 61 lb⋅ft (83 N⋅m) at 2500 rpm
• 1964–66 Austin-Healey Sprite MkIII, 59 hp (44 kW) at 5750 rpm and 65 lb⋅ft (88 N⋅m) at 3500 rpm
• 1964–66 MG Midget MkII, 59 hp (44 kW) at 5750 rpm and 65 lb⋅ft (88 N⋅m) at 3500 rpm
• 1965–68 Riley Kestrel/Wolseley 1100, 55 hp (41 kW) at 5500 rpm and 61 lb⋅ft (83 N⋅m) at 2500 rpm
• 1973–75 Austin Allegro, 49 hp (37 kW) at 5250 rpm and 60 lb⋅ft (81 N⋅m) at 2450 rpm
• 1975–80 Austin Allegro, 45 hp (34 kW) at 5250 rpm and 55 lb⋅ft (75 N⋅m) at 2900 rpm
• 1968–82 Mini Moke Australia only.
• 1975–80 Mini Clubman, 45 hp (34 kW) at 5250 rpm and 56 lb⋅ft (76 N⋅m) at 2700 rpm
• 1976–80 Mini 1100 Special, 45 hp (34 kW) at 5250 rpm and 56 lb⋅ft (76 N⋅m) at 2700 rpm

1071

The 1071 cc version was another one-off, this time for the Mini Cooper S. It used a new 70.6 mm (2.78 in) bore size and the 68.26 mm (2.687 in) stroke from the 848. It was only produced in 1963–1964. Paired with the even rarer 970 cc version, below, it became that rarest of things: an oversquare A-series engine.

Applications:

• 1963–1964 Austin/Morris Mini Cooper S, 70 hp (52 kW) at 6000 rpm and 62 lb⋅ft (84 N⋅m) at 4500 rpm

970

The Mini Cooper S next moved on to a 970 cc version. It had the same 70.6 mm (2.78 in) bore as the 1071 cc Cooper S but used a shorter 61.91 mm (2.437 in) stroke. It was produced from 1964–1965.

Applications:

• 1964–1967 Austin/Morris Mini Cooper S, 65 hp (48 kW) at 6,500 rpm and 55 lb⋅ft (75 N⋅m) at 3,500 rpm

1275

The largest A-Series engine displaced 1.3 L (1275 cc). It used the 70.6 mm (2.78 in) bore from the Mini Cooper S versions but the 81.28 mm (3.200 in) stroke from the plain Mini Cooper. It was produced from 1964 until 1980, when it was replaced by an A-Plus version.

Applications:

• 1964–71 Austin/Morris Mini Cooper S, 76 hp (57 kW) at 5800 rpm and 79 lb⋅ft (107 N⋅m) at 3000 rpm
• 1966–70 Austin-Healey Sprite MkIV, 65 hp (48 kW) at 6000 rpm and 72 lb⋅ft (98 N⋅m) at 3000 rpm
• 1966–74 MG Midget MkIII, 65 hp (48 kW) at 6000 rpm and 72 lb⋅ft (98 N⋅m) at 3000 rpm
• 1967–68 MG 1300/Wolseley 1300, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1967–68 Riley Kestrel 1300, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1967–68 Vanden Plas Princess 1300, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1967–73 Morris 1300, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1967–74 Austin 1300, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1967 MG 1275/Riley 1275, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3500 rpm
• 1967 Wolseley 1275, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3500 rpm
• 1967 Vanden Plas Princess 1275, 58 hp (43 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 3500 rpm
• 1968–69 Riley Kestrel 1300/Riley 1300, 70 hp (52 kW) at 6000 rpm and 77 lb⋅ft (104 N⋅m) at 3000 rpm
• 1968–71 Austin America (automatic), 60 hp (45 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 2500 rpm
• 1968–73 Wolseley 1300 (manual), 65 hp (48 kW) at 5750 rpm and 71 lb⋅ft (96 N⋅m) at 3000 rpm
• 1968–73 MG 1300 MkII, 70 hp (52 kW) at 6000 rpm and 77 lb⋅ft (104 N⋅m) at 3000 rpm
• 1968–74 Vanden Plas Princess 1300 (manual), 65 hp (48 kW) at 5750 rpm and 71 lb⋅ft (96 N⋅m) at 3000 rpm
• 1968 MG 1300/Riley Kestrel 1300, 65 hp (48 kW) at 5750 rpm and 71 lb⋅ft (96 N⋅m) at 3000 rpm
• 1969–71 Morris 1300GT, 70 hp (52 kW) at 6000 rpm and 74 lb⋅ft (100 N⋅m) at 3250 rpm
• 1971–82 Mini Moke Californian Australian only.
• 1969–74 Mini 1275GT, 59 hp (44 kW) at 5300 rpm and 65 lb⋅ft (88 N⋅m) at 2550 rpm
• 1969–74 Austin 1300GT, 70 hp (52 kW) at 6000 rpm and 74 lb⋅ft (100 N⋅m) at 3250 rpm
• 1971–80 Morris Marina, 60 hp (45 kW) at 5250 rpm and 69 lb⋅ft (94 N⋅m) at 2500 rpm
• 1971 Austin Sprite, 65 hp (48 kW) at 6000 rpm and 72 lb⋅ft (98 N⋅m) at 3000 rpm
• 1973–80 Austin Allegro, 59 hp (44 kW) at 5300 rpm and 69 lb⋅ft (94 N⋅m) at 3000 rpm
• 1974–80 Mini 1275GT, 54 hp (40 kW) at 5300 rpm and 65 lb⋅ft (88 N⋅m) 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 Rover K engine and an OHC version of the A-Series, ended in failure. During the development of what would 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' 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 998cc and 1275cc, the A-Plus had stronger engine blocks and cranks, lighter pistons and improved piston rings, hydraulic tensioner units for the timing chain and other detail changes to increase the service interval of the engine (from 6,000 to 12,000 miles). 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 80,000 to 100,000 miles 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 engines 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 998 cc and red for 1275 cc engines.

998 Plus

The A-Plus version of the 998 cc motor was produced from 1980–92.

Applications:

• 1980–82 Mini 1000/City/HL, 39 hp (29 kW) at 4750 rpm and 52 lb⋅ft (71 N⋅m) at 2000 rpm
• 1980–82 Austin Allegro, 44 hp (33 kW) at 5250 rpm and 52 lb⋅ft (71 N⋅m) at 3000 rpm
• 1980–90 Austin Metro, 41 hp (31 kW) at 5400 rpm and 51 lb⋅ft (69 N⋅m) at 2700 rpm
• 1982–88 Mini HLE/City E/Mayfair, 40 hp (30 kW) at 5000 rpm and 50 lb⋅ft (68 N⋅m) at 2500 rpm
• 1981–86 Austin Metro HLE 46 bhp (34 kW) and 52 lb⋅ft (71 N⋅m)
• 1988–92 Mini City/Mayfair, 42 hp (31 kW) at 5250 rpm and 58 lb⋅ft (79 N⋅m) at 2600 rpm

1275 Plus

The big 1.3 L (1275 cc) engine was also given the "A-Plus" treatment. This lasted from 1980–2000, making it the last of the A-Series line.

Applications:

• 1980–82 Austin Allegro, 62 hp (46 kW) at 5600 rpm and 72 lb⋅ft (98 N⋅m) at 3200 rpm
• 1980–84 Morris Ital, 61 hp (45 kW) at 5300 rpm and 69 lb⋅ft (94 N⋅m) at 2950 rpm
• 1980–90 Austin Metro, 63 hp (47 kW) at 5650 rpm and 72 lb⋅ft (98 N⋅m) at 3100 rpm
• 1982–89 MG Metro, 72 hp (54 kW) at 6000 rpm and 75 lb⋅ft (102 N⋅m) at 4000 rpm
• 1983–85 Austin Maestro HLE, 64 hp (48 kW) at 5500 rpm and 73 lb⋅ft (99 N⋅m) at 3500 rpm
• 1983–93 Austin Maestro, 68 hp (51 kW) at 5800 rpm and 75 lb⋅ft (102 N⋅m) at 3500 rpm
• 1984–89 Austin Montego, 68 hp (51 kW) at 5600 rpm and 75 lb⋅ft (102 N⋅m) at 3500 rpm
• 1989–90 Austin Metro GTa, 72 hp (54 kW) at 6000 rpm and 75 lb⋅ft (102 N⋅m) at 4000 rpm
• 1990–91 Mini Cooper, 61 hp (45 kW) at 5550 rpm and 61 lb⋅ft (83 N⋅m) at 3000 rpm
• 1990–91 Mini Cooper S, 78 hp (58 kW) at 6000 rpm and 78 lb⋅ft (106 N⋅m) at 3250 rpm
• 1991–96 Mini Cooper 1.3i/Cabriolet, 63 hp (47 kW) at 5700 rpm and 70 lb⋅ft (95 N⋅m) at 3900 rpm
• 1991–96 Mini Cooper S 1.3i, 77 hp (57 kW) at 5800 rpm and 80 lb⋅ft (110 N⋅m) at 3000 rpm
• 1992–96 Mini Sprite/Mayfair, 50 hp (37 kW) at 5000 rpm and 66 lb⋅ft (89 N⋅m) at 2600 rpm

1275 Turbo

Turbo versions lasted from 1983–90.

Applications:

• 1983–89 MG Metro Turbo, 94 hp (70 kW) at 6130 rpm and 85 lb⋅ft (115 N⋅m) at 2650 rpm
• 1989–90 Mini ERA Turbo, 94 hp (70 kW) at 6130 rpm and 85 lb⋅ft (115 N⋅m) at 3600 rpm

1275 MPi

A special "twin-port injection" version of the 1.3 L (1275 cc) engine was developed by Rover engineer, Mike Theaker. It was the last A-Series variant, produced from 1997–2000.

Applications

• 1997–2000 Rover Mini MPi 1.3i (TPi), 63 hp (47 kW) at 5500 rpm and 70 lb⋅ft (95 N⋅m) at 3000 rpm

JOHN COOPER GARAGES

During the 1990s Mini Cooper revival, John Cooper Garages offered a number of factory-approved "Cooper S" and "Cooper Si" upgrades to the standard Coopers. The conversions came with a full Rover warranty, and could initially be fitted by any franchised Rover dealer.

S pack (carb) 77 bhp (57 kW) – 1st Si pack (Spi) 77 bhp (57 kW) – 2nd Si pack (Spi) 82 bhp (61 kW) – 3rd Si pack (Spi) 86 bhp (64 kW) – 1997 Si pack (Tpi) 85 bhp (63 kW) @ 5500rpm – 1999 Si pack (Tpi) 90 bhp (67 kW) @ 6000rpm

See also

• BMC B-Series engine

References

Northey, Tom, editor in chief. World of Automobiles (London: Orbis Publishing, 1974), Volume 9, p. 1054, "Mini", and Volume 2, p. 121, "Austin Allegro."