began in 1971, ending in 1980. OHC version 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. Twin cylinder A-series 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. 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 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". 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. Current use This engine continues to be improved, it has a very large and wide market, whether this is classic car industry or 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