The BMC E-series engine is a line of straight-4 and straight-6 overhead camshaft automobile petrol engines from the British Motor Corporation (BMC). 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. The company's native United Kingdom market did not use the 2.6 L version, which was used in vehicles of Australian and South African manufacture. Although designed when the parent company was BMC, by the time the engine was launched the company had become British Leyland (BL), and so the engine is commonly referred to as the British Leyland E-series engine.
History
The E series was an overhead cam design, planned essentially for front-wheel drive use in the BMC range. It was intended to replace the transverse A- and B-series overhead valve designs used at the time in other BMC cars (but see also the O series, another replacement line for the B series). A purpose built production facility was built at Cofton Hackett south of Longbridge, Birmingham to build the units. The first use of the E series was in the Australian built Morris 1500 sedan and Morris Nomad hatchback followed by the front-wheel drive Austin Maxi five-door hatchback of 1969. These models were closely based on the ADO16 platform, but fitted with the 1.5 L E series. The 1500 was a four-door saloon, the Nomad a five-door hatchback which whilst bearing a similarity in looks to the Maxi, was an entirely local design.
The E series was always intended to provide larger capacity six-cylinder engines made on the same tooling as the four-cylinder. The 6-cylinder version was originally designed by Leyland's Australian division. These were intended for use in physically larger, more upmarket versions of UK and European front-wheel drive models, and for use in a mixture of mass-market front- and rear-wheel drive models sold mainly in the markets of Australia, New Zealand and South Africa. Using a common design saved time, but had drawbacks. The six-cylinder had to be short to fit transversely across the nose of a front-wheel drive car. To save such horizontal space the engines were long in stroke and had no water-jacketing between cylinder bores. The engines were very tall though, combining long stroke with OHC. This, together with the gearbox in sump design, forced a high bonnet line when the E series was fitted to smaller cars, something which infamously compromised the styling of the Austin Allegro, which was originally intended to sport a much sleeker appearance until it was decided by BL management that it would use the E series in its largest engine variants.
A higher compression version of the 1.7 was developed utilising a twin carburettor set up with increased valve lift and flat-topped pistons.
As fours and sixes shared production tooling, the four also had a long stroke and siamesed cylinder liners, even though it did not need the reduced width. This was especially true in later designs of transverse-engined BMC and BL cars, when the side-mounted radiator was moved to fit across the nose of the car reducing overall width of the engine considerably. The lack of water jacketing caused considerable development problems when the 1.5 L in the Austin Maxi needed an optional larger engine size. The 1.5 L four-cylinder E series could not be readily bored out, the placing of the gearbox directly underneath the sump made stroking the engine more difficult, and the Maxi was too narrow to accommodate a large-capacity six-cylinder. Overcoming these problems meant that even a modestly increased displacement, to , did not appear until 1971.
The engine was originally envisaged as a 1.3 and 1.5 L four-cylinder, with a 2.0 L six-cylinder created by adding two cylinders to the 1.3 L block. However, as development continued it appeared the 1.3-litre E series would not have any huge benefits over the 1.3-litre A-series being developed at that time from the existing 1.1, so the smaller E-series was dropped. The result was a saving in development capital for BMC, but also meant the six-cylinder had to be developed from the 1.5-litre block, creating its unusual engine size of .
Later derivatives
The four-cylinder E series was effectively discontinued when the Allegro went out of production in 1982. However it was substantially redesigned into the R series, and later the S series in the mid-1980s. The R series was effectively a stop-gap solution for the Austin Maestro, and is all but identical to the E-Series, the main difference being modifications to take an end-on transmission, in place of the BMC 'transmission-in-sump' arrangement. The S-Series was a more thorough redesign, featuring a belt-drive camshaft in place of the E-series chain and a completely new cylinder head.