Pamplona in Spain, NMQ (Nueva Montaña Quijano) between 1966 - 1975; The Austin Motor Company A-series is a British small straight-4 automobile engine.

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.

All engines had a cast iron head and block, two valves per cylinder in an OHV configuration and sidedraft SU carburettor.

"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.

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.

Paired with the even rarer 970 cc (59 cu in) version, below, it became that rarest of things: an oversquare A-series engine.

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.

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.

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.

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.

To allow the MG Metro to compete with larger, more powerful hot hatchbacks a turbocharged version of the 1,275 cc (77.8 cu in) A-Plus was developed with the assistance of Lotus Engineering.

A Garrett T3 turbocharger was fitted along with a unique SU carburettor with an automatic pressure-regulated fuel system.

The turbocharger was fitted with an advanced two-stage boost control system which only allowed full boost to be achieved at engine speeds above 4000 rpm - this was to prevent damage to the sump-mounted four-speed gearbox, the design of which dated back to the early 1950s and could not reliably cope with the high torque output of the Turbo engine at low speeds.

The MG Metro Turbo was entered in the British Touring Car Championship in 1983 and 1984, with the tuned engines producing in excess of 200 bhp (150 kW).

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.

It was redesign of existing 948 cc version, new purpose-designed cylinder head, with Lucas CAV fuel injection.

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.

The lack of investment and the turmoil and chaos in British Leyland, meant the engine never reached production.

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.

[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.

Almost every part of the engine is still made, whether in original specification or improved versions, pistons, camshafts, crankshafts, cylinder heads.

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.