BMC A-series engine

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".[1] 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.

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 998 and 1,275 cc (60.9 and 77.8 cu 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 6,000 to 12,000 miles (9,700 to 19,300 km)). 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 (130,000 to 160,000 km) 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 998 cc (60.9 cu in) and red for 1,275 cc (77.8 cu in) engines.

1275 MPi

Japanese Mini Paul Smith engine, notice the side radiator

MPi A-Series

A special "twin-port injection" version of the 1.3 L; 77.8 cu in (1,275 cc) engine was developed by Rover engineer, Mike Theaker. It was the last A-series variant, produced from 1997 to 2000. Few changes were made to ensure the engine complies with Euro 2 (later Euro 3) emission standard, such as adding a 3-way catalytic converter and making it twin-point injection, the engine also receive changes with ignition system by having a wasted spark instead of the distributor. For the Japanese domestic market. the engine maintained the single-point injection version of the engine and the radiator is still on the side due to the space constraint for the air conditioner component.

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 (Mpi) 85 bhp (63 kW) @ 5500rpm
• 1999 Si pack (Mpi) 90 bhp (67 kW) @ 6000rpm[2]

The diesel version appeared in 1962, on the BMC Mini tractor. It was developed with the help of Ricardo Consulting Engineers. It was redesign of existing 948 cc version, new purpose-designed cylinder head, with Lucas CAV fuel injection. 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. It uses Ricardo-patented "Comet V" combustion chambers, with a compression ratio of 23.6:1. Produced 15 hp at 2500rpm and 38 lb⋅ft (52 N⋅m) torque at 1,750 rpm. 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. Production ceased in 1969.

At the end of 1965, BMC South Africa started a new program, with the aim of using more components manufactured in the country (using less imported components from U.K.). They decided to develop and manufacture their own version of the engine. Two versions were made with 1.1 and 1.3 litres, using the same cylinder block. The block was redesigned, new oil circulation arrangements and redesigned main bearing (bigger dimensions) and stronger/biffers camshafts. Both versions use the same connecting rods, but different crankshaft and pistons. Prototypes versions were made by 1969. Production began in 1971, ending in 1980.

The A-series design, along with particularly the B-Series, was licensed by Nissan of Japan. Many changes were made for the initial OHV Nissan C engine and the succeeding E and E-1. An early change was to incorporate a five-bearing crankshaft. The cylinder head was modified by swapping plugs and ports, plugs fitted between pushrods and eight 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 formed the basis for many of their following engines, notably the later OHC Nissan E engine]], was scaled up into the Nissan CA engine which culminated in the DOHC 169 PS (124 kW; 167 bhp) CA18DET. The basic design was also scaled down into the Nissan MA engine. All these engines show their lineage by the characteristic un-skirted crankcase block of the BMC A-series, but with the A and E having the camshaft moved to the right side allowing greater port areas, and a mounting on the right wall of the crankcase for the oil pump, whereas the BMC A-series had the oil pump at the back end of the left-side camshaft.

With the intention of updating the current engine, for use in the new Mini Clubman (ADO20), and current ADO16, Leyland developed an OHC version. It appeared in a prototype version in 1971, with single overhead camshaft. It featured redesigned cylinder block, new aluminium cylinder head and twin SU carburetors. Eleven prototypes units were built, in three different capacities, 970, 1070 and 1275 cc. All engines use the same cylinder bore dimension of 70.6 mm, to reduce the number of engine parts, reducing production costs. It uses a modular approach, making it possible to produce the three versions with the same engine block. The lack of investment and the turmoil and chaos in British Leyland, meant the engine never reached production. In 1975 the plan was abandoned in favour of the "A+" version that reached production in 1980.

Under the code ADO11, a 474cc twin cylinder with a single H2 SU carburetor based on the 948cc unit was built with the intention to be used in ADO15 (Mini) with an in-sump gearbox.[4] In May 1957, the engine was tested in one Austin A35, alongside a 20 hp 500cc air-cooled later 670cc water-cooled 2-cylinder two-stroke engine developed by Dr Joe Ehrlich of EMC Motorcycles[5] that was tested in one Austin A30 before being used in an experimental Austin A30 based prototype with weight reduced to 584 kg (by way of a special lightweight body in steel that was a couple of gauges lighter than normal with altered panels to keep weight at a minimum) known as the Austin A20 or the "Lightweight Austin 7".[6]

In 2021 retired racing driver and Bugatti specialist Ivan Dutton rebuilt an example of the 4 stroke engine from an original head and cylinder block and documented the work on Youtube. He also has the EMC 2-cylinder two-stroke engine which he plans to return to running condition.

This engine continues to be improved, it has a very large and wide market, whether in the classic car industry or the racing industry. It has a wide OEM manufacturer support. Almost every part of the engine is still made, whether in original specification or improved versions, pistons, camshafts, crankshafts, cylinder heads. Cylinder heads are available in 8v or 16v, made in aluminium with 5, 7 or 8 ports. Additionally over the past few decades it has not been unusual to see the A-Series stretched beyond 1275cc with capacities ranging from as low as 1293cc up to 1479cc, although it is commonly enlarged to 1380cc while retaining its reliability so long it is serviced regularly and well looked after. [7]

The A series engine is currently used in David Brown Mini Remastered. The engine is totally rebuilt, with new internals to an improved specification. The engine used is based in 1275cc MPi version, with larger capacity versions including the 1330cc Monte Carlo [8] as well as the 1380cc and 1450cc Oselli Edition. [9]

• BMC B-series engine
• Rover K-series engine
• Rover L-series engine
• Tritec engine

• Northey, Tom (1974). World of Automobiles. Orbis Publishing. p. 1054.
• Robson, Graham (2011). The A-Series Engine: Its First Sixty Years. Haynes. ISBN 978-0-85733-083-3.

Wikimedia Commons has media related to BMC A engine.

• "A-series engine". The Unofficial Austin-Rover Web Resource. Archived from the original on 27 September 2007. Retrieved 13 April 2005.
• "Turbo Minis". The No.1 Turbocharged A-series resource. Archived from the original on 9 April 2005. Retrieved 13 April 2005.