The BL O-Series engine was a straight-4

Straight-4

The inline-four engine or straight-four engine is an internal combustion engine with all four cylinders mounted in a straight line, or plane along the crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons driving a common crankshaft....

 automobile

Automobile

An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...

 engine family produced by British Leyland (BL) as a development of the BMC B-series engine

BMC B-Series engine

The BMC B-series was a straight-4 internal combustion engine family, mostly used in motor cars, created by British company Austin Motor Company. The pre-cursor of the "B" series engine was a 1200 cc OHV engine which was used in the 1947 Austin A40 Devon. This A40 Devon engine was based on a...

 family. (See also another B-series successor, the BMC E-series engine

BMC E-Series engine

The BMC E-series engine was a straight-4 and straight-6 overhead camshaft automobile petrol engine from the British Motor Corporation . It displaced 1.5 L or 1.8 L in four-cylinder form, and 2.2 L or 2.6 L as a six-cylinder...

.)

Introduced by BL in 1978 in the rear wheel drive Series 3 Morris Marina

Morris Marina

The Morris Marina is a car which was manufactured by the Morris division of British Leyland in the UK throughout the 1970s, which was a period of great turbulence and difficulty for the British car industry. It was known in some markets as the Austin Marina, Leyland Marina, and Morris 1.7...

 and the smaller engined versions of the front-wheel-drive Leyland Princess

Leyland Princess

The Princess is a family car that was produced in the United Kingdom by British Leyland from 1975 until 1981. The car inherited a front-wheel drive / transverse engine configuration from its predecessor, the BMC ADO17 range...

, it was intended to replace the 1.8 L B-Series unit. The main advance over the B-Series was that the new unit was of belt driven overhead camshaft

Overhead camshaft

Overhead cam valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods...

 configuration, with an aluminium

Aluminium

Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

 cylinder head.

Offered in the unusual capacity of 1.7 L as well as 2.0 L, it proved to be reliable and was widely used in BL vehicles. These included the rear wheel drive Morris Ital of 1980 (1.7 L or 2.0 L with an automatic gear box), the rear wheel drive Rover SD1

Rover SD1

Rover SD1 is both the code name and eventual production name given to a series of large executive cars made by British Leyland or BL through its Specialist, Rover Triumph and Austin Rover divisions from 1976 until 1986....

 of 1982 (2.0 L only), and 1.7 L and 2.0 L in the front wheel drive Austin Ambassador

Austin Ambassador

The Austin Ambassador was a medium-to-large hatchback car model introduced by British Leyland in 1982. The vehicle was a heavily updated version of the Princess, an ageing model that had lacked a hatchback...

 — in fact the only engine offered in this model. In 1984, it was reworked for installation in high specification 2.0 L versions of the front wheel drive Austin Maestro

Austin Maestro

The Austin Maestro is a compact-sized 5-door hatchback car that was produced from 1983 to 1994, initially by the Austin Rover subsidiary of British Leyland , and from 1988 onwards by its successor, Rover Group. The car was produced at the former Morris plant in Cowley, Oxford. It was initially...

 and Austin Montego

Austin Montego

The Austin Montego is a British mid-size saloon car that was produced by the Austin Rover subsidiary of British Leyland , and its successors, from 1984 until 1994. The Montego was the replacement for the Morris Ital, to give British Leyland a modern competitor for the Ford Sierra and Vauxhall...

, where it was later optionally available with fuel injection or turbo-charging. This installation of the O-Series was adapted for use with the Honda

Honda

is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...

 PG-1 end-on manual gearbox, replacing the gearbox-in-sump design traditionally used on British Leyland front-wheel-drive products. The 1.7 L O-Series was not used in these vehicles, which featured R- and later S-Series 1.6 L units.

In 1986, BL collaborated with Perkins to convert the O-series to run on diesel. The oil-burning versions, known as the Rover MDi or Perkins Prima, proved to be highly successful in the Maestro and Montego, and helped sustain the ailing mid-sized models into the 1990s. Perkins successfully marketed the engine under its own brand in the industrial and marine sectors.

By 1987, British Leyland (now known as the Rover Group

Rover Group

The Rover Group plc was the name given in 1986 to the British state-owned vehicle manufacturer previously known as British Leyland or BL. Owned by British Aerospace from 1988 to 1994, when it was sold to BMW, the Group was broken up in 2000 with the Rover and MG marques being acquired by the MG...

) equipped the O-Series with a 16-valve cylinder head for the Rover 800

Rover 800

The Rover 800 series is an executive car introduced by the Austin Rover Group in 1986 and also marketed as the Sterling in the United States. Co-developed with Honda, it was a close relative to the Honda Legend and the successor to the Rover SD1....

. This 2.0 L unit was known as the M-Series

Rover M-Series engine

The Rover M-Series is a 4-cylinder, DOHC internal combustion engine introduced by the Austin Rover Group in 1986 for the then-new Rover 800-series....

, and was further reworked into the T-Series

Rover T-Series engine

The Rover T16 engine was a 1994 cc petrol engine, produced by Rover from 1992 to 1999. It has a bore of and a stroke of . It is a development of the M-Series , which was in turn a development of the O-Series, which dated back to the BMC B-Series engine as found in the MG B and many...

 in 1992. The original 8-valve version of the O-Series was also briefly used in budget versions of the Rover 800.

2 litre O-series

A notable advantage of this particular O-series engine is that the cylinder head does not require modification to run on unleaded petrol due to having hard enough valves. Other O-series engines, however, cannot run on unleaded without modification of the cylinder head or use of an additive.

Cars using the O-series

Examples of cars using a version of the O-series engine:

• Austin Maestro
  Austin Maestro
  The Austin Maestro is a compact-sized 5-door hatchback car that was produced from 1983 to 1994, initially by the Austin Rover subsidiary of British Leyland , and from 1988 onwards by its successor, Rover Group. The car was produced at the former Morris plant in Cowley, Oxford. It was initially...
  
   2.0 L, 2.0 L Diesel
• Austin Montego
  Austin Montego
  The Austin Montego is a British mid-size saloon car that was produced by the Austin Rover subsidiary of British Leyland , and its successors, from 1984 until 1994. The Montego was the replacement for the Morris Ital, to give British Leyland a modern competitor for the Ford Sierra and Vauxhall...
  
   2.0 L, 2.0 L Diesel
• Princess / Austin Ambassador
  Austin Ambassador
  The Austin Ambassador was a medium-to-large hatchback car model introduced by British Leyland in 1982. The vehicle was a heavily updated version of the Princess, an ageing model that had lacked a hatchback...
  
   1.7 L, 2.0 L
• Morris Ital
  Morris Ital
  The Morris Ital was a medium-sized saloon car built by British Leyland from 1980 until 1984.-Design and launch:The Ital was first launched on 1 July 1980. It took its name from Giorgetto Giugiaro's ItalDesign studio, who had been employed by BL to manage the re-engineering of Morris Marina, a car...
  
   1.7 L, 2.0 L automatic
• Morris Marina
  Morris Marina
  The Morris Marina is a car which was manufactured by the Morris division of British Leyland in the UK throughout the 1970s, which was a period of great turbulence and difficulty for the British car industry. It was known in some markets as the Austin Marina, Leyland Marina, and Morris 1.7...
  
   1.7 L
• Rover SD1
  Rover SD1
  Rover SD1 is both the code name and eventual production name given to a series of large executive cars made by British Leyland or BL through its Specialist, Rover Triumph and Austin Rover divisions from 1976 until 1986....
  
  2.0 L