Designed and specially built to become the Corporation’s new mid-sized engine, the E-Series had a troubled early life, but eventually matured into something very worthwhile indeed.
New engine, new factory; new start?
By the mid-1960s, it had become clear to BMC’s management that, in order to maintain sales volumes, the company would have to produce a new mid-sized car to replace the Farina saloons. The plan for the BMC 1800 to do this had gone by the wayside in light of its increased girth, price and ambition, meaning that the older car would have to soldier on for some time longer…
As it was, the new mid-sized car (the ADO14), which began to emerge from BMC during 1965/66, was an interesting design, which Sir Alec Issigonis planned to be a technological leader in its field. Reflecting BMC’s confidence when this plan called for an all-new body and an all-new engine.
Initial thoughts were that the new engine (codenamed the ADO32) should be light and compact, and displace about 1300cc. Issigonis was sold on the idea that upward expansion of his engine should be achieved by the addition of two extra cylinders (a principle he also explored on the DX engine used in the gorgeous 9X), which meant that there would be little need for expansion through boring/stroking and that, in the search for compactness, ADO32 could get away with siamesed cylinder bores.
The original design soon grew
At the original displacement of 1300cc, the six-cylinder version of the engine (codenamed the ADO25) would displace almost 2-litres; a size that would pitch it perfectly within the executive market, alongside Rover and Triumph’s less sophisticated offerings. It was noted by Jeff Daniels in his book, BL: The Truth About The Cars, that this plan was soon pulled apart by two factors:
1) The A-Series was being developed into a very useable 1300cc engine and, although in 1966, it was still considered an exotic unit for use in the Mini-Cooper, productionised versions were on their way.
2) The accountants dictated using ADO17 doors, which set the ADO14’s practical wheelbase at just under 105-inches at the very least – that would be far too big for a 1300cc engine.
These factors meant that ADO32 would need to be expanded to 1.5-litres and, in turn, ADO25, to 2.2-litres.
A new factory site chosen to build it
As Longbridge and Cowley were at capacity churning out A-Series engines for the ultra-successful Mini and 1100, a new factory would need to be built to produce the new engines; especially at the volumes that BMC anticipated for it! The site chosen was Cofton Hackett, and it went up during 1967 and 1968.
Sadly, the new engines (christened E- and E6-Series) were launched after Leyland’s takeover of BMC and, because of the ADO14’s (Maxi’s) less-than-sparkling performance, it was soon decided by the new management that the E-Series would need to be enlarged in order to develop more torque and power.
According to Daniels, Harry Webster had his work cut out extending the E-Series unit, but finally managed it by stroking it just enough as not to foul the transmission-in-sump gearbox internals. The fact that moved the new engine extremely close to the 1800cc B-Series engine, was purely incidental…
The engine grows and becomes a six-cylinder
The larger version of the four-cylinder E-Series engine duly appeared in 1970 (eighteen months after the launch of the original Maxi), and it silenced many criticisms of the 1968 Maxi. In HL form, it produced 72bhp, but this was upped later, when a twin-carburettor version putting out 91bhp was added.
What about ADO25 – the E6 engine? That first appeared in the 1970 Austin Kimberly/Tasman, then the domestic ADO17 two years later. Blessed with exceptional smoothness, it received a warm welcome on the marketplace, but was a little overshadowed by the age of the car it was in (the ADO17 was eight years old at this point).
The E6-Series engine, rather oddly, displaced 2227cc (which based it on the 1485cc version of the four-cylinder E-Series engine), and it did make commentators wonder about whether a suitable 2.6-litre version could be produced.
Along with the Maxi, the E-Series engine found its way into the Allegro in 1973 and the E6-Series, into the Princess in 1975… and that was about it. All European installations were transverse front-wheel drive, but Leyland Australia saw an advantage in using it in the Marina (longitudinal, rear wheel drive) and P76…
The E-Series in Australia
By Merv Sheather
In Australia, the E-Series first came to light as the means to upgrade the ADO16’s power and torque. Fraught with inherited engineering problems at launch, the Morris 1500 had several technical gremlins (cable backlash, no detent plungers, third motion shaft circlip detachments, due to designed selective fit ‘v”-groove retention circlip).
The 1500 was a sales disaster, due to widespread press reports of these gearbox failures, and it forced the Australian subsidiary to accelerate the introduction of the Marina.
The Marina was released with the E-Series engine in 1500 and 1750 four-cylinder forms, as well as a 2622cc six-cylinder version, conceived to compete with local market cars from GM Holden, Chrysler and Japanese imports.
The E-Series did not have a considerable power output gain when it jumped from 1500 to 1750cc. To overcome the advice from the Marketing Department (about the small hike in power compared with the 1500), the Engineering Department down-rated the output of 1500cc version by adding a pressed metal choke sleeve in the induction manifold below the carburettor – hence the ‘detune’ modification of a manifold choke – this really was a ‘desperate act ‘ by the Engineering Department to comply with Marketing Department’s requests.
The 1750cc was seen a ‘market adequate’ by the Marketing Department (when compared with the main competitors’ engines). The main problem was that the output of the 1500cc engine in standard tune was far too close to the developed bhp of the 1750cc unit.
As the Marketing Department stated at board level, “the buyers only read engine output, for example , bhp figures and very rarely consider the torque at rpm figure”. A smaller 1 1/2-inch SU carburettor was used and not the 1 3/4 inch SU carburettor as was used on the Morris 1500. Many owners became aware of the simple change to get increased power and removed this pressed in metal sleeve.
The model range had moderate sales success until the Zetland/Waterloo Plant closure which occurred in November 1974.
Utilised also in South Africa from CKD kits supplied by Leyland Australia for both Marina and Leyland P76 vehicles. E-Series six-cylinder used in South African for locally assembled P76 cars had a 2 inch SU to give higher top end performance gain.
Note: South African Rover SD1s used the E6-Series engine in 2622cc form, and it compared very favourably with the domestic, Triumph-derived, Rover 2600.
The E-Series’ fate…
So, did the E-Series see out its days in the Maxi and Allegro, and the E6-Series in the Princess? Sadly, the E6 died with the Princess in 1982, but the four-cylinder version continued…
One thing that the E-Series proved in the end, was that it was long-lived. During the late 1970s, it was developed for use in the LC10/LM10 (after dropping the O-Series) with an end-on Volkswagen gearbox.
Interestingly, the LC10/LM10 version, dubbed the R-Series was produced in 1598cc form (half-way between the E’s 1485cc and 1748cc) and, according to contemporary Austin-Rover technical briefings, this were the perfect size for the unit, using existing valves.
The R-Series was a stepping stone, though; an anomaly that lasted 18 months (for political reasons), until the S-Series engine appeared in 1984. And the S-Series? This was an extensively revised version of the R-Series engine.
This unit lasted until 1993. Product plans from the early 1980s spoke of a diesel version of the S-Series engine, for use in the stillborn Austin-Rover AR6… We have yet to uncover any evidence to suggest this engine ever left the drawing board.
Is the Editor of the Parkers website and price guide, formerly editor of Classic Car Weekly, and launch editor/creator of Modern Classics magazine. Has contributed to various motoring titles including Octane, Practical Classics, Evo, Honest John, CAR magazine, Autocar, Pistonheads, Diesel Car, Practical Performance Car, Performance French Car, Car Mechanics, Jaguar World Monthly, MG Enthusiast, Modern MINI, Practical Classics, Fifth Gear Website, Radio 4, and the the Motoring Independent...
Likes 'conditionally challenged' motors and taking them on unfeasible adventures all across Europe.