Engines : The E-Series

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.

Keith Adams
Latest posts by Keith Adams (see all)


  1. One VERY rare car was the MG Maestro 1.6 with the S series engine.Only produced for approx 6 months before the 2.0i MG version was launched.

  2. my parents had a 1.6 hls meastro with this engine it was not the best trying to start the car when the engine was hot was a weakness the car leaked water they could not find where it was comming from either

  3. A proper and powerful workup of the E series six –which resembles the Nissan 240Z — might have been a genetically acceptable basis for the retro Healeys that have been attempted over the years. The Haldane four with Ford power and the Harrier with V8 have been tasty, but somehow wrong, and not making the proper sort of sounds. In no place do I see bore / stroke dimensions. Modern piston heights allowed longer rods and or strokes to be accommodated in existing blocks, so the requisite 2.6 litre capacity might now be attainable.

  4. Hi Merv.great efforts about explaining what happened in Australia with this engine. I have tried in vain to Find any existing P76 ‘s in South Africa. I beleive all the 650 CKD packs ended up in new Zealand where they were assembled there (in pretty much v8 form only). I have tracked down photos of later SD1 E6 engines which ran the twin Su set up of the earlier Kimberly or UK Austin 2200’s but in 2.6(ex Australian tooling 6 cyl form. They also adapted power steering to the E6 blocks something that was not used in Aus p76 E6 production.
    If you have any P76 South african E6 inormation I would like to know.I have seen planned 1975 and beyond Zetland export program of fully Bult up P76 and Force 7 production scquedules which were only about 40 cars per month initially. The marina was fitted with this engine in 1750 and 2600 form in SA and the Victoria park E6 production line and transferr equipment went to capetown for that very reason.
    Cheers Nick

  5. In terms of power output how does the 2.6 E6 in the South African SD1 compare with the 136 hp 2.6 SD1-Six in the standard SD1?

    One figure has the 2.6 E6 putting out 121 hp, yet if was compared very favourably with the domestic Triumph-derived Rover SD1 2600 rated at 136 hp then I am assuming that the E6 produced a similar output to warrant such a comparison.

    • Having driven a South African SD1 with the 2.6 E6 (known as the R6 over there), I can confirm that subjectively there was no appreciable difference in performance between it and the Rover 2600 engine, so I think it must have produced at least 130hp. Just like the 2.2 litre version, it felt turbine-smooth….much better than the Rover engine. To set the record straight, the Rover 2300/2600 engine was designed by Triumph, but was totally new, not a development of the previous Triumph straight-6.

      • Actually the Triumph six, at least in two litre form, as fitted to the Triumph 2000 in the mid-sixties, was an odd feeling engine in that it didn’t have the usual turbine smoothness of other contemporary sixes used in the Holdens, Falcons, and Valiants of the era. It sort of felt like ‘rough, noisy, big four’ and revving it out to it’s maximum rpm of 5,000 it sounded ‘thrashy’ and unhappy. Even the 1500cc Fiat Crusader could outperform it in acceleration and top speed, which from memory was just 90mph, and zero to 50mph taking well over 10 seconds.

  6. 2.6 E6 engine as built and used in South Africa, fitted with twin SU HIF-6 carburettors as standard, produced 82kW @ 4750RPM and 202N.m torque @ 2200rpm. Max usable rpm is 5000.

    • Johan, 82kW (110hp) was the power output of the 2.2 E6, so it’s hard to imagine that the 2.6 was tuned to give the same power for ordinary car applications, although a torquier lower powered version might have been produced for its installation in the Land-Rover Series 3.

  7. @ 7
    82 kw equates to 110bhp. That’s what the 2.2 litre version used in the Princess produced. I would like to think the 2.6 version was rather more.

  8. The Australian E6 in 2.6 litre form developed 121HP @4500rpm (90KW) & 165 lb/ft Torgue @ 2000Rpm (224NM). Remember this is in single carb form (HS6 1.75″), so I think in Twin carb form, the comparison with the 136Hp English Triumph/Rover SD1 2600 is Valid

  9. Has anyone ever tried a 2.6 with 3 MG1600 webber DCNFs? I would estimate power to be 150 -160 BHP

    • Russ, the weber carbs on the MG Maestro 1600 were a nightmare to keep in tune, so fitting 3 of them to an E6 would just multiply the problems by 50%. I would rather fit 3 SU carbs, and sacrifice a few hp for reliability and ease of maintenance.

    • Remember reading elsewhere about a still-born project by Leyland Australia to develop a more potent version of the 2.6 E6 with that same 150-160 hp target for use in possibly the Marina or another car as well as the E6 allegedly even being capable of being bored out to around 3.0/3.1-litres.

  10. I’d Imagine that to be right and again begs the question why it was not put in the MGB and in the 3 ltr.

    • A twin-carb 1500 engine was fitted to the Allegro 3 Vanden Plas 1.5, but they were very low volume so I think you would be hard-pressed to find one at a breakers yard. If it’s performance you’re after, a 1750 engine in single or twin-carb form would be much better, and probably easier to find.

  11. I was always confused by the Princess having E6 but not the 1748cc E4. Surely the twin carb was a better bet than the 1.8 B-series plus it had 5 speed’s. The E4 would have been comparable in performance to a 4 speed 2.0 O-series and more frugal not to mention below the 1800cc tax bracket. But reading a road test only BL could launch a 6-pot 2200 HL with 4 speed and vinyl trim!

    • I thought the same as you Susan. The twin-carb 1750 from the Maxi produced 91hp, giving it a useful performance advantage over the single-carb 1800 B-series, plus the overdriven fifth gear would have given both improved fuel economy and more relaxed cruising. I suspect the main reason the E4 wasn’t used was because of its 5-speed gearbox, a feature not available on the supposedly higher-spec and more expensive 2.2 E6, so it would have looked a mis-match in the range progression. It would be a very simple job to fit the E4 into the Princess, but I’m not aware that anyone has ever carried out such an interesting and practical conversion.

  12. This was part of BLs problem, producing so many different engines competing with each other. In 1300 you had the A series or the Triumph ohv unit, the 1500 E series vs the 1500 Triumph engine, 1750 e series vs 1.8 B series vs 1850 slant 4 triumph, 2600 sd1 vs E6, rover v8 vs stag V8 Etc

  13. Lyle gallant, BL made twin carb 1500 e series from the factory, used in Allegros. The twin carb manifold/carb set up from one of those or a 1750 maxi would be a bolt on swap.

  14. Apparently in Issigonis’s biography a sketch exists detailing proposed dieselized versions of the 1500cc and 1750cc E-Series engines, presumably to replace the dieselized B-Series engines.

    • Nate – I rather doubt that any E4 diesels were ever built because their power outputs would have been so similar to the 1500 and 1800 B-series diesels. But back in the early 1970s, I had occasion to visit the Light Diesel Development Dept, which was situated in the East Works in a separate building alongside the main factory. While there, I had a nose around, and I clearly remember seeing a 2.2 E6 diesel!

      • Perhaps it would have been too similar to the B-Series diesels, though in 1.5/1.6 E4 form it might have allowed for a earlier dieselized 1.6 S-Series that was later considered during the AR6 project.

        It is curious that a dieselized E6 (let alone a dieselized SD1-Six) was never considered for the Range Rover and Rover SD1, which instead received the VM Motori engines (after the Rover V8-based Project Iceberg was cancelled).

  15. The E6 was an extremely smooth and powerful engine for its day. It transformed the Landcrab into something that could take on a Triumph 2000 and was smoother than the 2 litre engine used in Rovers. In the Princess, it made a relaxing car into an even more relaxing one, with a useful turn of speed over the four cylinder cars.

  16. That original idea of producing a 1300 four, which would be expanded with 2 cylinders into a 2000 six is truly bizarre, for a car which was theoretically designed to replace the Farinas with their 1600 B series engine.

    The 2000 E6 could have been a direct replacement for the 1800 B, but surely they would still need an engine around the 1600 mark?

    • A 1600cc 4 cylinder engine could have a 2400cc 6 cylinder counterpart.

      Maybe a larger bored or stroked version of the 1300 could have been made, considering this did happen with the E series but 200cc bigger.

      • It just seems that the engine was designed to be expanded by adding more cylinders, rather than just the usual bore and stroke adjustments. Sadly this seems to be another engineering blind alley BMC went down…

        “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”

        • Volvo in the 1990s came up with a modular engine design that could be tailor made, though with different bores & strokes.

          Ford had already produced the Essex units with 1.6, 2.0, 2.5 & 3.0 capacities, though the V4s were quite rough running. I did wonder if a V8 version was planned, diesels certainly were.

          Even before that many manufacturers had 4 & 6 cylinder versions of the same engine.

          • Would be surprised if a Ford Essex V8 variant displacing around 3.3-4.0 was planned given the Essex V4/V6 engine’s 60° vee angle though it might have made the likes of the Zodiac and Zephyr less forgettable.

          • I was thinking the V angle was wrong, though there are a few exceptions to the rules over the years.

          • A few years ago I read that the Zephyr/Zodiac MkIV- Project Panda had been designed the way it was with its huge bonnet to accomodate V8 power and/or 4wd. I have no idea if the planned V8 was to be Essex related. There were a few 2.5 litre 4wd prototypes built some being used by the police.

          • Have read about both the Project Panda and the 4WD prototypes, seems likely that Ford were looking at fitting the Windsor V8 into the Zephyr/Zodiac mk4 though nothing came of it.

  17. Thought I read somewhere that the E was originally supposed to be both a 1.1 and a 1.3 four which would have give a 1.75 and 2.0 six

    • You read it on here on the Maxi development story:

      “Initially the E-series engine was planned with four different capacities, 1160cc, 1300cc, 1485cc four cylinder units plus a 2227cc six cylinder version of the 1485cc engine. Contrary to previous accounts, the two smaller units were never built leaving the 1485cc and 2227cc engines to be developed by BMC’s engineers. The first 1485cc engine began testing in March 1966 followed by the first six cylinder unit in July. By September 1966 ADO16 and ADO17 mules were road testing the new engines. Very early on it was decided the E-series engine needed more torque and by October 1967 a 1748cc and a 1797cc unit were being tested. The extra capacity was created by lengthening the stroke.”

  18. Often wonder why the E series didn’t go to 1.6 litres well before the R/S. It would have given a capacity that aligned with Ford’s Pinto and Kent units and therefore in line with 1970s market expectations, by the sound of it the unit worked at its best at that capacity and it would have left clear blue water between the 4 cylinder E and 1.8 litre B. It would also have created a 6 cylinder unit of 2.4 litres that would have served well in the SD1 rather than the expensive, low volume Triumph derived OHC unit and have sat rather better than the 2.2 version above the 2.0 O series when the Princess 2 came along.

    • In fact reading the other posts above there is the intriguing thought that if a 1.3 E series – as originally planned – had been produced along side the 1.6 4 cylinder the E could have provided a range of engines from 1.3 4 cylinder to 2.4 litre 6 cylinder. The virtually all BL’s engine needs could have been rationalised around the E. Only the Rover V8 unit and smaller capacity A series would have been needed to top and tail.

      • Have read conflicting accounts on the 1300 E-Series ranging from it being as underdeveloped as the existing E-Series engines to it being far superior to the 1500cc/1750cc E-Series and competitive against the 1275cc A-Series.

        Find it difficult to believe that the 1300cc E-Series was competitive against the 1275cc A-Series given that the 1500cc A-Series put out around 68-77 hp or 83 hp with the Special Tuning conversion.

      • If they had produced 1.1, 1.3 and 1.6 engines then using the origional logic of moving to a six that would have given 1.75, 2lt and 2.4 six cylinder engine. Expanding that logic a little to include 8 cylinder engines would have produced 2.2 2.6 amd 3.2 V8’s

        Similar exersise were being carried out at BMW. The plan makes sense for BMC but none at all of BL which probabaly explains why nothing come of it.

        Still a Miget with the 1.5E an MGB with the 2.0/2.2/2.4/2.6 E6
        , the maxi with a 1.6 E4 1.75/2.0 E6

        Landcrab with 2.0/2.2/2.6 E6

        AD016 with 1.1, 1.3. 1.6 E4

        Mini with 1.1, 1.3. 1.6 E4

        Marina with 1.6 E4, 1.75 E6 2.0 E6

        Allegro with 1.6 E4, 1.75 E6 2.0 E6

        Austin 3 litre with 2.6 E6, 3.2V8

        Could definately have transformed the fortunes of the BMC middle and upper model rang, but pick for me would be an E6 (or EV8) engined MGB.

        Now I’m definately in the land of make believe ;@)

        • drae

          Expand that logic further with the 1.75 E-Series 4-cylinder and you would effectively get a 3.5 V8 OHC E-Series which would not only cover the Austin 3-litre and MGB, but also potential resolve the supply problems that plagued the Rover V8 whilst allowing the later to retain its exclusivity for use in Rovers, Land / Range Rovers, Morgans and TVRs as well as potential for further expansion and development.

          That is not even mentioning the 1915cc overbore used in the Allegro rally car.

  19. Wasn’t the 1.5 E Series also used in the Midget? I can imagine it working well there, where the decent output once revved – but poor low end torque – would suit the car.

    Poor low end torque was a major shortcoming in my dad’s 1.5 Allegro estate with the 4-speed autobox, although above about 2,000rpm the engine pulled well for its size. Smoothness was much better than an A series engined Allegro across the power range.

  20. We often wonder how good the E6 with fuel injection and five speeds could have been if this was introduced in the Princess and carried over into the Ambassador. This could have really taken on the 2.3 V6 versions of the Cortina and the Granada and been a worthy alternative to the Rover 2300 and improved Princess sales. Also the Ambassador would have gained a real boost to sales by continuing with the E6.

  21. Within the realms of “What IF?” where my imagination’s been venturing whilst reading the above, I’ve also been pondering the possibility of what type of amazing animal the “MGD” – a.k.a. ADO21 – would’ve been IF it’d been given the green light. The original (UK) E6 was slated to power the top-end model of this futuristic mid-engined “Ferrari-Dino-206GT lookalike” – but what IF the stroked, 2.6-litre version would’ve found its way to the car’s ‘mid’ position, just behind the driver’s spine. Imagine the lusty but silky smoothness of such a great British Grand Touring cruiser. What a lost opportunity!

  22. All up my family owned 4 15oo E series motors and the big issue was the shim adjustment of the valve clearance and the constant production updates…..there were three different head gaskets and every set of points that I bought had to be pulled apart and rebuilt as they were incorrectly assembled and earthed out internally due to a plastic spacer being put on top of the metal bits instead of in between them.

    Imagine that? Car running a bit rough, put in new points and plugs and car doesn’t start at all. Took us all weekend to fix and only realised the problem when we put the old points in again as a “last throw of the dice”….car started first go, we took the new points back to dealer for replacement and the new, new set did the same thing. Eventually compared new with old and noticed the problem…..told dealer, didn’t care, he was trying to sell P76 V8s by that stage…..

  23. Does any info exist on what bore and stroke the 1160cc / 1300cc E4 and 2000cc E6 had?

    Was thinking that in hindsight the E4 would have been better in 1390cc (same bore / stroke) and 1598cc, slotting above the A-Series and below an 1.8-2.0 O-Series.

    • 1160cc and the standard 76,2mm bore would have been achieved with a 63,6mm stroke, 1300cc would have been around 71mm.
      Not sure these verslons would have used this standard bore, though, so strictly theoretical.

  24. “Issigonis was sold on the idea that upward expansion of his engine should be achieved by the addition of two extra cylinders”

    A mistake back then, but 50 years later that’s what manufacturers are doing with modular engine design. Both BMW and JLR are going for 500cc per cylinder engines, hence the 2L 4 cylinder engine, the 3L straight 6 cylinder engine, the BMW (and future JLR) 1.5L 3 cylinder engine…

  25. BMW & JLR also have the option of a 5 cylinder 2.5l engine.

    Just this week I was puzzling out the combinations of a modular engine family, using Volvo’s as a basis.

    Ford’s engines for the Zehpyr were fairly modular by the standards of the day, being 4 & 6 cylinder units with the same bore & stroke.

    Morris was on the same path with the post war Oxford & Six engines using 4 & 6 cylinders of the same dimensions, but with different valve gear.

  26. Is there any (logical) reason why the E6 could not be fitted with the Maxis 5 speed gearbox? Since the gearbox was designed for the E-series engine it just seems strange that ADO17 and 71 sixes were never given this option.

    • Perhaps because it was a gearbox in-sump? I could image technical adaptations would be needed to install a box designed specifically for the four cylinder with the E6.

      • The box finally used with all FWD E6 installations was a Landcrab box using a different casing. It seems that the Maxi box was not designed to carry the high torque and load from the heavy 2200 cars, while the original 1800 box was tremendously strong, yet very heavy. The automatic Maxis (and Allegros) used a development of the Mini and ADO16 automatic AP 4-speed gearbox, while the 1800, 2200 and all Princess and Anbassodor models used a special version of the Borg-Warner 35 3-speed box. The reason again would be the maximum torque available on the B-, O- and E6-engines being too much for the AP-design.

        • I suspected as much. It is so typical of BMC/Leyland to miss an opportunity that is at their fingertips. In view of the fact that the E-series was planned as a four and six cylinder from the outset- why couldn’t they develop a 5-speed gearbox that a) handle the torque of the E- and b) be suitable for use with the 1.8 B-series? It would have given ADO17 and the later Princess a valuable USP over its rivals with relaxed cruising and class beating fuel economy. Or would the Wolseley Six then eclipse the Rover and Triumph 2000 models?

  27. I learnt to drive on a 1500 E Series Maxi. The Maxi had a lot to commend it, but the drivetrain was not one of them. The gearchange was … tough and approximate, and the engine revved and sounded like it was made of masonry. Even as an R Series, refinement was pretty poor, but the S Series was a pretty refined and powerful unit – better than Ford’s Pinto, but worse than GM’s Family II of that era.

    • The 1500 was poor in the Maxi, my family had one and it was underpowered and thirsty, although the engine was far better in the Allegro with a lighter body. Better, though, was the 1748 E series, which made the Maxi into a more refined and faster car, and the ultimate was the E6, which turned the ageing ADO 17 into a car with Jaguar like refinement and a good turn of speed, and also made the Princess into a very nice car to drive and ride in. Indeed the E6 proved to be a far more reliable engine than the six cylinder Rover engines, and could have been bored out to 2.3 and 2.6 litres.

  28. Very interesting comment above. The limitation of the E Series engine was it’s height. It was considerably taller than the A Series and in smaller capacity versions (1.1, 1.3, 1.5, 1.6) required a much higher bonnet line. This was shown in the Allegro where the original styling was corrupted to accommodate the E Series 1.5 & 1.75 engines. Without these the bonnet height would have been lower and the styling more acceptable. Even the Ambassador had a lower bonnet than the Princess, once the decision was made to drop the E6.
    The E Series was designed primarily for fwd and thus needed to be narrow in the engine bay. Therefore the stroke was relatively long and there was no water between the bores, thus limiting any option to bore out the block.
    I owned two 1750 Maxi’s over the years. Both had a rod gearchange and both were delightful cars for their room and ride. Engine power was adequate but my second was a new vehicle and I fitted twin carbs (the HL was not available at that time). These made it a much more exciting vehicle. The engine was quiet and there was no disadvantage in a chain driven ohc. (Today most manufacturers are going back to chain-driven ohc e.g. Subaru due to longevity and reliability!).
    The E6 concept of adding another two cylinders is very practical from a production and tooling point of view. Shared transfer tooling, together with pistons and rods etc is exactly what Morris did in 1950 and Jaguar/Land Rover do today with the Ingenium engine series.
    The E6 could/should have been developed into a performance version, although the E2.6 may have been a challenge with its longer throw stroke.
    The E Series would have been a great engine for mid mounting, as the height would no longer be a problem.
    BMC/Leyland should have concentrated on a family of engines maximising shared components and transfer machinery. Ideally they should have considered all-alloy construction, however this probably would have been too risky. Even the much later K Series has big issues. It took Honda to show how it could be done reliably.
    Likewise they should have standardised and produced the planned 5-speed gearbox family of 66/77/88mm. The Triumph gearbox used in the Marina was rubbish, but the 77mm as used in the Rover SD1 was excellent. These gearboxes could have been incorporated into fwd versions.

    • An obvious solution to E-series heigth issue would have been to develop an end-on gearbox in stead of a gearbox in sump (though not sure E6 would still have fitted east-west; but as advocated elsewhere, and at the risk of boring this site’s regular readers: a modular 400 cc per cylinder E-series could have given us a 1.6 E4, 2.0 E5 and 2.4 E6. An E5 with end-on gearbox and eventually fuel injection would probably have sufficed for BL’s fwd needs had the Maxi been a properly developed fwd hatchback in the mould of the Renault 16 or VW’s Passat. The 2.4 E6 (120-130 hp with carbs, 150 or more with FI, very smooth in both forms) would have been perfect for SD1 and SD2, eliminating the need to develop the new Triumph/Rover 6-cylinder in the proces).
      Just image what could have been had this modular E-series been improved by the people form Triumph who developed the Triumph Sprint engine and later the M/T16…

      • As one who was involved in engine developments around the 1970’s to mid 80’s I can perhaps shed a little light on what has been proposed here. The ‘E’ series engines were considered sufficient for the UK market but were nowhere near ‘clean’ engines and by the time US spec ‘smog’ regulations were applied were the proverbial ‘couldn’t pull a skin off a rice pud’!

        The big problem with all the Longbridge sourced engines was the appalling combustion system, with the exception of the ‘A’ and ‘B’ series engines which had both benefited from Harry Weslake’s intervention early on in their life to impart the ‘heart’ chamber. The ‘E’ engine had a single OHC and direct valve operation, with no intermediate mechanism, this meant the valves were canted towards the centre line of the chamber and resulted in a ‘M’ shaped chamber in cross section. This resulted in a very poor flame front propagation and worse dictated that the ports feeding the valves were equally poor performing.

        This is the reason the engines had poor low speed torque, poor fuel economy and the ignition characteristics became the standard by which all future engines would be judged, i.e is it better than the ‘E’. Answer – only if its not an ‘O’.

        The ‘E’ was meant to be a cheap engine to produce – I remember seeing around 1978 a cost breakdown which showed its target cost was £135 for E4 and £182 for E6. The ‘actuals’ were £149.50 for E4 and £213 for E6.

        • Very well put Martin, The Australian production actually made the fours and sixes on the same line, which I’m told was also used for the 4.4 V8 when that went into production. I recently compared the 2.6 figures with hose of the Aus Holden 161 used in the Torana LC (local Vauxhall) and the figures are 125hp at 4800 and 150 lb/ft at 2800. not startling but from a much older pushrod engine. Oddly the 2.6 leyland engine in the Marina was rated at 110 hp while the same engine in P76 was 121hp. I don’t think the valve angle is due to the OHC as Rover used a very similar setup on the 2000 engine with straight inline valves. The South African sixes must have had better than quoted performance as they had both twin carbs AND larger bore split exhaust from the Kimberley.

          A direct comparison with the SD1 six is complicated because they were downrated ;so as not to outpower the V8 (or future Jag sixes) I suspect. The cylinder head on the Sd1 engine is also reported to be copied from the Dolly sprint 16 valve head. i’ve often wondered how the six would go the a 24 valve head?

          • Holden Torana 161 was available in 3 power levels – 108bhp/146lb-ft (lc), 114bhp/157lb-ft (hc) or 125bhp/149lb-ft (GTR). Marina was 121bhp/165lb-ft (according to factory service data), so almost as much power as the GTR, and a lot more torque. A twin carb Marina Six would have easily been 135bhp, not far behind the heavier XU-1 on power to weight ratio.

        • Is it known to what degree the features on the original belt-driven crossflow-headed prototype engine that became the E-Series accurately reflects what appeared later on the S-Series engine?

          If Daniel Richmond was able to improve the existing engine with his upgrades, surely Harry Weslake could have done the same along with anyone else that could have advocated for hardened valve seats.

          It was initially said to have been schemed as a direct replacement for the A-Series at a time when there was little certainty the A-Series could be stretched to a road-going 1275cc engine, before Issigonis decided to use it as a starting point for a relatively more conventional if overambitious one-size-fits-all replacement for all of BMC’s engines (via upward expansion through a pair of extra cylinders) and basically succeeding Leonard Lord’s stillborn V4/V6 engine designed by Duncan Stuart from about 1956-1962. The experimental E-Series prototype was said to be roughly contemporaneous with the V4 engine canned in 1962 prior to the start of ADO14 circa 1964-1965.

          Along with Alec Issigonis’s influence could BMC’s financial problems over the course of the 1960s together with the UK being denied EEC entry in 1963 have also played a role in paring down and constraining the E-Series engine’s development to how it eventually became by the time it reached production?

          Fwiw BMW would embrace a similar idea around that time with the modular M113 prototype engine that can be best described as a more M20-sized 1.3-litre four / 2.0-litre six precursor to what eventually became the upsized M10 four / M20 six. The fact a smaller company that was almost bankrupt a few years prior was able to further improve on an idea (from M113 to M10/M30) to suit its needs against a much bigger company that could not or was unwilling to do the same with what became the E-Series to replace the B-Series and C-Series merely highlights how bad things were at the time.

          Curiously the E-Series also makes for an interesting comparison with the Nissan A OHV and later Nissan E OHC engines (essentially being an all-new design that integrated Nissan’s improvements to the licenced built B-Series and later derivatives), which shared similar maximum 76mm bores with the latter two being compliant with US emissions regulations and even being redesigned in 1974 to incorporate its NAPS emissions control system.

          The Nissan A/E engines also appear to have roughly similar 82.5mm bore pitch as the E-Series prior to Nissan upscaling the E OHC design to create the larger CA/CD engines and unlike the E-Series managed to stay within its design brief without being mutated into something it was never intended to be.

  29. A thought occurs.

    Why not use cylinder liners & suitable piston sizes for varying capacities as well as stroke in the E?
    That way you could have 1100/1300/1500/1800 fours, 1650/1950/2250/2700 sixes & a 3000 & 3700 v8 all from identical blocks with the added advantage that the more utilitarian sizes would be the most bomb proof (all things being equal). Saving on machining in the first place – upgradable later (back in those days it wouldn’t be difficult to swap liners & pistons).
    If we say an 1800 single carb managed 72hp (which seems low compared to B series 86hp) and a TC 92 then fuel injection would give 81 and 103 respectively. That would give 3.7 v8s of 162 & 206hp respectively – more than useful figures for the time and arguably better (very likely smoother) than the Rover V8 (192hp? in twin plenum form).
    I guess the only penalty would be weight?

    • Have come to embrace the notion of the E-Series in fully unleashed form becoming BMC’s version of the Volkswagen EA827, a venerable configuration capable of 3*/4-cylinder to if necessary even 10/12-cylinder petrol as well as diesel engines.

      Like the 2-litre EA827 4-cylinder a direct E-Series analogue could have butterflied away the need for the 2-litre O-Series, if the turbocharged 275 hp Volkswagen Golf A59 prototype is any indication such an engine in turbocharged form could have even adequately replaced the 2-litre M/T-Series Turbos whose internals were said to be capable of reliably putting out around 275 hp (the gearbox being the limiting factor for the latter).

      Am not sure where it could have probably replaced the A-Series for smaller cars though, even Volkswagen were driven to develop the compact EA111 a downsized version of the EA827 for the Audi 50 / Volkswagen Polo yet BMC had the 9X engine which itself appears to share some elements from the E-Series.

      On the V8 front one only needs to see the 1988 3.6-litre Audi V8 that basically used a pair of EA827s to create a V8 or possibly even a 90-degree V6 which might be derived from the V8.

      The above though depends on BMC properly developing the E-Series in tandem with adopting an end-on gearbox arrangement for its FWD cars so the tall block is less of an issue.

      *- 3-cylinder versions of the EA827 were looked at for Wartburg and Trabant in petrol and diesel forms, it was also the case that experimental 3-cylinder versions of the E-Series were looked by BL.

      • If I’m not mistaken, a 3-cylinder version of the 1485 E4 was the basis for the ECV3’s 1113 engine, which in turn formed a development starting point for the later K-series.

        • Likely the case given the similar displacement between the ECV3 unit and the 3-cylinder version of the 1485cc E-Series, yet BL around that period were also said to have looked at 3-cylinder versions of the Triumph Slant-4 with some even claiming it was what formed the starting point for the later K-Series (and not the E-Series).

          • Is there any substantiation to those claims? Seems a little unlikely as the Slant 4 was (wait for this…) a slant engine and K wasn’t.
            BTW: as I understand it, this 3-cylinder E-engine wasn’t really the starting point for K, merely a starting point for it’s eventual devvelopment.

            Speaking of Slant 4: any ideas why both Triumph(/Saab) and Vauxhall in the 1960s seem to have thought in future they could do without a six cylinder engine when developing their Slant 4s/V8s, as I never read about any related (Slant or V) 6s?

          • Have not been able to substantiate those claims regarding the Triumph Slant-4, it is probably in terms of 16-valve technology used in the Dolomite Sprint as well as the sandwich construction as used in the stillborn 2-litre Triumph Sabrina Twin-Cam engine. – http://mgf.ultimatemg.com/group2/engines/development_history_of_the_K.htm

            No idea why the likes of Triumph, Saab and Vauxhall opted for the Slant-4 / V8 engine layout, perhaps they felt any related (slant / 90-degree V-angle) 6-cylinder down the line was an acceptable compromise for a related family of engines.

            Heard other carmakers opted for such a Slant-4 / V8 layout including Volvo (via Redblock plus unproduced V8), Porsche, allegedly BMW (via M10) and possibly one or few more.

      • Also: wouldn’t E-series’ cast iron block and head have prevented development of a (viably light)V8 from it?
        On the other hand: had E-series been properly developed by the combined BL engineering might, the Triumph people would possibly have added a new (most likely alloy) cylinder head, solving this issue as well.

    • Re. E-V8: I guess E-series cylinder blocks and heads being cast iron did indeed not help. Also, I suppose there wasn’t a real necessity to develop another V8: relatively few were required anyway, Rover’s was doing very well, Triumph’s was still under development and Jaguar were also working of a V12-related V8.
      Not to mention the limited resources at BMC and BL, nor the underdeveloped nature of the actual E-series…

      • Would guess the only benefit to an E-V8 based on the E-Series already in production would be to remedy the production capacity issues with Rover producing the V8.

        Perhaps a 90-degree V6 would also be an option, though would have preferred a similar solution to developing a 60-degree V6 that Fiat’s Dante Giacosa adopted with the 128 SOHC 4-cylinder and 130 V6.

      • An E8 only makes sense if BMC continues without Leyland. After the merger.the Rover V8 could be used and was used in the MGB and was at least looked at for the Austin 3 ltre. Also the Daimler V8s were available.

        BL did not want BMC to continue making large saloons or even sports cars. so the idea does not fly.

        The E6 on the other hand sat nicely in the very gap that both Rover and Triumph had in their line ups with the ancient Triumph 6 and the big four Rover engines not being up to the job. Thus we got the new Rover 6 engines that ended up in the SDI

        The whole point of the E4 was to facilitate mid range 6 spin offs, in the original design capacities of 1.2 to 1.4 the equivlant E6 would be 1.8 and 2lt. The ideal size for a mid range car to go face to face with 3 series and lower end 5 series BMWs. On the larger stroke engines we get a 2.2 and 2.6

        Of course Triumph would rather die in ditch then let use a Rover engine never mind an Austin engine.

        The E 4 and 6 could and should have been more widely used in both the Marina, Princess, MGB, SD! and TR7

        The only rational for not doing this would be the adoption of the Dolomite engine. available in 1.8 and 2 ltre 4. and yet this engine only ever appeared in the Dolomite and TR7.

        No attempt was made to make the Dolly engine a 6 and it was never considered as an entry level engine for the SD1

  30. Forget about the E series re turbo charging it was hard enough to keep the head gaskets from blowing between cylinders as it was.

    • In production form would have to agree (though the later 1.6 S-Series powered 150 hp Janspeed Rover 216 Vitesse Turbo was said to have been pretty decent), am merely taking the E-Series similarities with the EA827 to its logical conclusion had BMC properly developed the engine from the outset (albeit without significant input from Issigonis given his mixed record at best in developing engines).

  31. 2 other problems with E, long single link chain that ran around both sides of the water pump and was riveted together so required reriveting on replacement unless you were game/ stupid enough to run a split link.
    The combustion chambers were set at an angle to the engine centre line to keep the length down, the exhaust ports ran across the width of the head, steam engines run on this principal, Henry Ford made the same mistake with his first V8, this is why your arms ache when filling the cooling system

  32. Given the later related S-Series notably allowed the Montego to feature a lower bonnet line, what prevented the E-Series from having the height of the block significantly reduced during its development?

    Was it simply due to the E-Series being conceived as a related 4/6-cylinder engine family unlike the S-Series or were there other factors which led to the E-Series being unnecessarily tall and thus negatively affecting the styling of the Allegro?

    One gets the impression that on top of being easily being capable of improvement in a number of respects to become a late-60s British precursor to the VW EA827 (e.g. 88.5mm bore centres, possible crossflow head, further tuning by Downton and sans siamised bores, etc), the E-Series could have been much shorter than it ended up being by the time it was signed off for production.

  33. Wasn’t that the result of a combination of there tuinhek?
    * narrow bores/block thus long stroke/high block
    * overhead camshaft, making it a little higher
    * transmission in sump, making the combination even higher

    As the gearbox wasn’t very succesful anyway, I think an end-on one would have been the obvious remedy. R- and S-series had longer strokes than the 1,5 litre E-series, so their blocks would have been comparable, the main difference being in their gearboxes.

    • That is some of the factors though it seems height was significantly reduced in the S-Series for it to slot under the Montego’s bonnet, which was not the case in the stop-gap R-Series engine used only in the Maestro itself a lightly modified E-Series.

      • OK, interesting. Was it really the engine itself or could it perhaps be auxiliaries too, such as the air filter that seems smaller on S-series than on R?

        • Not sure of the specifics, the S-Series reduction in height may have possibly come from the block being chopped (by how much is not made clear) along with the valve gear being made more compact.

          Nevertheless the possibility of the S-Series being built from E-Series tooling with little modifications as feasible over the E/R-Series, would suggest in better circumstances during development a more S-Series like E-Series could have potentially saved Harris Mann’s envisaged styling for the Austin Allegro (even despite the latter’s in-sump gearbox layout) as well as had other knock on effects. Specially since the S-Series was reputedly only nearly 12kg more than the A-Series (not that an S-Series like E-series would have been an adequate replacement for the A-Series).

      • The S series was also compact enough to fit under the bonnet of the Honda designed SD3 Rover 200

        • Agreed and with EFI no less, which for whatever reason was not carried over to the Maestro and Montego.

          Aside from a number of differences with its rather promising early-60s belt-driven 1.3-litre OHC ancestor that became the unadventurous yet compromised E-Series, have to wonder to what extent the S-Series ultimately reverted to resembling something closer in concept to the original experimental design.

          It is interesting to compare what became the E-Series with that of a certain smaller company at the time on the verge of bankruptcy in the late 50s to early 60s. Who built on the earlier foundation of a 1960 0.9-litre engine with 93mm bore centres to develop a 1.3-litre with the same bore centres with the ability to spawn a modular 2-litre inline-6 that same year, prior to building on the 1.3-litre unit to develop a 1.5-litre unit with 100mm bore centres in 1961-1962 that would itself spawn a whole range of 4-cylinder units up to 2-litres and later 2.5-3.4-litre 6-cylinder engines.

          • Nate, would that smaller company be a certain Bavarian Motor Works? I guess there were two inherent differences (besides company culture and -lack of- money money) that prevented comparable development: E-series being (very) long-stroke and having more limited bore centres, don’t you think?

          • To be fair it is not exactly clear what the bore centres let alone the bore/stroke of the experimental belt-driven 1.3-litre OHC E-Series ancestor was intended to be, not the bore/stroke of the initial stillborn 1.3-litre E-Series for that matter compared to the 1.5 E-Series production engine.

            Like BMW with what eventually became the M10 engine after an additional 7mm increase in bore centres, BMC could in retrospect have also carried over aspects of the experimental 1.3 OHC onto one with increased bore centre spacing from 82.5mm by about 6mm at minimum (or 0.5mm more than the VW EA827’s 88mm bore centres) yet without the limitations of the siamised bores.

            The 2-litre EA827’s bore/stroke was 82.5mm x 92.8 mm, while the 1.5-litre EA827’s bore/stroke was 76.5 mm × 80 mm compared to the E-Series’s 76.2 mm × 81.3 mm. A properly developed E-Series with the existing 95.75mm stroke could if deemed necessary archive 2-litres with an 81mm stroke at minimum (the Honda B20A featured a bore/stroke of 81mm x 95mm with the Mitsubishi 4G94 featuring a bore/stroke of 81.5mm x 95.8mm), if not a still undersquare 2-litres without such a long-stroke like on the EA827, Mitsubishi 4G9 and a few others.

            Graham Robson’s book on the A-Series makes mention of an F-Series engine with similar features as the experimental belt-driven 1.3-litre OHC engine that became the basis for the E-Series, however he claims there was no apparent link between the F-Series project and the E-Series (though to be fair the latter was significantly changed from its original promising design by the time it was ready for production).

            The 5-bearing F-Series was conceived as a possible contender to replace the A-Series encompassing the 1.1-1.3 category and intended for both transverse and longitudinal layouts, with prototypes being a square engine of equal 74mm bore/stroke that ran for 200 hours before the project was cancelled in the early 70s without being fitted into cars.

  34. Nate – one of the other issues for the Allegro was not just the height of the engine – it was also the heating system which was described by either Harris or Paul Hughes as being truck sized!

    • With the bulky heating system originally being developed for the Marina at astronomical cost before being carried over to the Allegro, one wonders both what rationale prompted BL to make it that size to begin with as well as whether more compact heating systems were considered for both the Allegro and Marina (either existing or other alternatives)?

  35. I know this commenyt was made years ago, but do you have any further information about this overbored 1915cc Allegro Nate? Was that the E4 engine, or an O-series? (I had thought the siamesed bores of the E4 (done to keep transverse engine width down to make a transverse E6 possible) precluded boring any further than the 1750?

    Reason it is so interesting is that, a 1915cc E4 would have given a 2872cc E6, which really would have made the E4/E6 a viable engine family to replace the A, B, O & C series engines, with consequent significant cost savings to BL that could have kept it afloat, or allowed better technical development (like strengthened maxi 5 speed gearbox for E6, and adapting Triumph 2500PI Lucas fuel injection to fit E4 & E6).

    They could have had destroked 1L, 1.3, 1.6, 1.75 to fit the 1.8 tax class, and a 1.9 in E4, and the 1.3, 1.6 and 1.9 give a 2L, 2.4 and 2.9L E6. and a transverse E8 straight 8 of 3.8L from the 1.9 would just fit the wider large car bodies and given a decent powered range to rival Ford & GM big sixes that were so popular (think P76).

    • Originally recall seeing the 1915cc Allegro in an article on an old issue of Practical Classics a few years as it was used in the 1750 Austin Allegro Works Rally Car (of which a Vangaurds model was made).

      The only online reference would be to Google – Engine Punk: Vintage Thing No.23.2 – Austin Allegro, there it is mentioned the 1750 Austin Allegro Works Rally Car used a 160+ hp E-Series bored out using Fiat pistons to around 2-litres (or 1915cc as recalled in the old Practical Classics article).

      However it was not viable for a road-going production car since oil consumption was catastrophic along with fuel consumption due to the fat weber DCOE carb, together with the existing E-Series engine’s limitations including the siamised bores and smaller bore centres.

      The curiously similar Volkswagen EA827 (that was originally conceived as a similar 1200cc unit) would be a more realistic benchmark for what the E-Series could have become had it did away with the siamised bores, featured EA827-like bore centres as well as a shorter more compact block akin to the later S-Series along with possibly featuring a crossflow head.

      Even the 275 hp 2-litre Turbocharged engine in the stillborn Volkswagen Golf A59 prototype is basically the equal of what the standard 197 hp 2-litre M/T-Series turbo engine is truly capable of putting out were it not for the limitations of the PG1 Powertrain gearbox used by Rover.

      Such an engine could have indeed replaced the B/C-Series and butterflied away the O/M/T/L-Series engines though doubtful whether it could have adequately replaced the A-Series if the 1.3 EA827 is any indication (suggesting it would have not have been an improvement over the A-Series), even Volkswagen themselves replaced the 1.3 EA827 with the larger 1.3-litre small-block EA111 engines.

    • Was that just the same head in different material or was it different (i.e. crossflow design) and if so, do you know aanything about the resulting output?

      • Sorry, additionally: according to Wikipedia, S-series had a competely redesigned engine head. E-series had Weslake-designed kidney-shaped combustion chambers, so how about S-series? I think I can see cross -flow design on some drawings on the interent, but not sure…
        Also, Wikipedia says R-series, “like the E-series” had an aluminium head; I thought the original E-series head was cast iorn, wasn’t it? Perhaps the aluminium came with the S-series redesign?

  36. Wow, thanks Nate! Have read the Engine Punk article you mentioned, and what jumped out at me about the 160+ hp rally 1915cc E4 was “… oh yes, all on a standard gearbox too.” Presumably the standard 5 speed E4 gearbox, which Leyland Australia deemed too weak for the E6 Marina (and even the 1st gear in the B series 4 speed box they used for the 2.6L E6 was blanked off to protect it from the 165lb ft torque). So perhaps that 5 speed box had more capability than BL thought?

    The fuel consumption doesn’t bother me – Webers are notoriously thirsty; the SU carb seems the optimal blend of power and economy. Similarly, high oil consumption seems more likely to be either poor fit of the Fiat pistons to the bore, or more likely the typically Fiat practise of slightly ‘loose’ oil control ring to lessen ring wear and friction power losses.

    I was more concerned the 1915cc capacity may have stretched the bore to the point of more frequent head gasket failure, but that wasn’t mentioned as an issue.

    The siamesed bores and narrow width between bores was mostly an issue for exapnding capacity, and for colling, but given adequate radiator and fan that doesn’t seem to be an issue either – certainly not for our 1750 Maxi when heavily laden up hills 😉

    But even if 1750cc was the largest E4 capacity realistic for factory production, the family of 1.3, 1.5 and 1.75 E4, with 2 and 2.6L E6 and a 3.5L E8 would have radically reduced stock the BL factory and global dealers had to stock, while using the spare E4 capacity at Cofton Hackett from lower than expected Maxi sales, and freeing other factory space from A, B, O, C engines.

    Crucially, narrowing the engine range to 1 family cuts stock holding costs, machine tooling costs (at a time when many engines required expensive retooling), and would have freed up R&D staff to improve the E range and boxes, fuel injection, etc.

    Fascinating stuff to ponder. Thanks for the extra info! 🙂

    • Am not really convinced a 2-litre E6 could have adequately replaced a 2.0-litre B/O-Series/etc, let alone whether a 1.3-litre E3 could replace the A-Series. Also see there being large gaps in displacement had the existing E-Series capacities been used as a template.

      A properly developed E-Series family could have definitely replaced the B/C-Series and taken on a similar role to the O/M/T/L-Series had the 4-cylinder grown to 2-litres, like the Volkswagen EA827 it could have also formed the basis of inline-5 (in place of Td5 aka Project Storm) as well as (likely) 90-degree V6 and V8 engines (the latter making up for the Rover V8’s production capacity limitations). It also seems the E-Series was developed with dieselization in mind based on Issigonis’s notes, together with tales of experimental E6 diesels/turbodiesels as well as the 1.6 S-Series diesel / turbodiesel considered for the later Rover AR6 project.

      Had the money been available and the company been inclined, it is also possible such an engine family could have developed a related V10 (akin to a doubled-up EA827 inline-5 and was previously considered by Volkswagen for the Porsche 928 before being revived many years later) as well as an E-Series derived transversely mounted narrow angle V4/V6 engine plus W8 in place of BMC’s earlier attempt at a narrow-angle V4/V6 (the Volkswagen VR5/VR6 reputedly being derived from the EA827 with the W8 being another related engine).

      At best the company could have ideally had two engine families (technically 2 and a half engine families with the A-Series playing a similar economy focused role as the Renault B-Type or Fiat 100 Series units). One a fully developed E-Series family that encompasses inline-4, 6-cylinder and V8, etc engines with displacements beginning from 1500cc+.

      The other a small 970-1600cc inline-4 based on A-Series principles (possibly even forming the basis of an 730-1200cc inline-3 in place of the sub-998cc A-Series) appearing ideally in the early/mid-1960s featuring a bore range of 70.6mm-76mm and a stroke range of roughly 62mm-88mm that indirectly replaces the A-Series. Being in essence a British version of the Austin-derived Nissan A OHV* / Nissan E OHC with elements of the Renault C-Type (plus petrol/ethanol “Ford CHT” engine) and later Renault E-Type engines, prior to being superseded by a distantly related engine akin to the present day petrol / diesel Renault K-Type (appears the latter was also capable of spawning LPG and possible ethanol / flex-fuel variants).

      *- Basically the indirect slightly upscaled A-Series successor would adopt a similar evolutionary approach reminiscent of how the B-Series became the O/M/T/L-Series/Td5/etc (or even Volkswagen with their own range of EA111 and EA827 descended engines), as opposed to more costly clean sheet approaches that the company could ill afford at the time.

  37. Zebo i cannot remember the specs.
    , the E6 marina used a Borg Warner gearbox, it was the original Healey that had first gear blanked off.
    The gearbox in the 4 cylinder Marina was a Truimph unit.

    • OK, too bad, but thanks for responding. I like to think that E-series could have become much better with a different head, modified by Tirumph and/or Rover engineers (plus an end-on gearbox).
      Must admit I don’t know if later R- and/or S-series had the original E-series engine head in different size, does anybody know that? I suppose so as those were equally coarse, but not sure. Nate, perhaps?

      • Sorry, additionally: according to Wikipedia, S-series had a competely redesigned engine head. E-series had Weslake-designed kidney-shaped combustion chambers, so how about S-series? I think I can see cross -flow design on some drawings on the interent, but not sure…
        Also, Wikipedia says R-series, “like the E-series” had an aluminium head; I thought the original E-series head was cast iorn, wasn’t it? Perhaps the aluminium came with the S-series redesign?

  38. !500 and 1750 both had the same bore, the e6 manual transmission was the one used by Chrysler in the Valiant,t the other 3 speed unit was in the Freeway/ Wolseley 24-80 using the 6 cylinder B series “blue streak” engine.

  39. With proper planning, by the end of the 1960s BMC/BL could have dropped all their old rwd models, and updated and expanded their fwd model range.

    If they had utilized the variants that were productionised overseas, then the range could have been :-
    ADO22 “Marina”, in 3-box booted saloon, 5-door hatch and 3-door estate, using 1300 and 1600 e-series, with 4 or 5 speeds. This would have taken on the mk2 Cortina. Riley and Wolseley versions could have had upmarket nose with quad headlights.
    Maxi, but sized halfway between ADO22
    Marina and Tasman, with 1600 or 2000.
    Tasman 2000 to replace the 1800.
    Wolseley 6/125, 2400 Kimberley based to replace Wolseley 18/80 and 6/110.

  40. The E6 was an engine designed for very relaxed cruising rather than high performance. It was ideally suited to the Princess, where it made the relaxed nature of the Princess even better by offering almost silent cruising at the motorway speed limit. The E6 could be thirsty, with urban fuel consumption in the low twenties, but it was the best engine in the British Leyland range below the V8s and Jaguar engines for quiet long distance driving.
    Also, why was the Ambassador denied the E6 as it would be suited to such a large car, whose four cylinder engines were lethargic and not as refined? Mind you, the Amby was an exercise in cost cutting from the detailing to the low rent interior.

    • Yes the E6 was refined, but it was thirsty and therefore sold poorly. It was also no more powerful than the 2L O series. Now I love six pots and and given the choice would have one over a four, but it was somewhat inadequate as an engine. Maybe better as a 2.6 but too weedy as a 2.2.

      • @ Standhill, maybe the E6 would have been more economical if it was used in conjunction with a five speed transmission and given a hike in power. Remember, when this engine was launched in 1972, it nearest Austin Morris rival was the 1.8 B, and it offered a considerable improvement in power and refinement, particularly in the ADO17 and the early Princess. I suppose when the Princess received the 2 litre O, the difference in performance was only 3 mph, and arguments for keeping the thirstier E6 were becoming more difficult. Yet if it was upgraded and mated to a five speeder, the engine would have been given more justification.

        • Although the e6 was extremely smooth, it didn’t really cut the mustard in the performance stakes because of its long stroke under square design. By the time the Ambassador was coming out we had the Cavalier with smooth punchy and economical 4s with smaller capacities. In fact the O series was behind the rest of the pack….

        • Maybe so. After I posted that comment I got to thinking about other contemporaneous engines and I don’t suppose 104bhp was particularly feeble really. Triumph’s 2000 only had 90bhp to play with. Vauxhall’s 2.3 slant four was rated at 108, and the 2 litre Pinto was under 100bhp I think. So maybe not weedy after all. It did like a drink though.

          • The pinto was dependent on the model. In standard form it was 99bhp, while mild tune by Ford was built with 109. However, it was hugely tuneable with its crossflow head, and in the 80s with Electronic Fuel injection it could do 114bhp in standard tune, while Cosworth took it, gave it a new DOHC aluminium head which powered the infamous Sierra and Escort in their name. My old man had a twin carb 2.0 in his Cortina Mk3. Over 200,000 miles, mild tune for 109 bhp, which kept on going fir a few more thousand miles in a lot higher state of tune in Stock car racing. It was a rough old dog, but tough as old boots.

      • The twin carb 2l O-series in the Ambassador had 100bhp and 120lb/ft, less than the 110bhp and 124lb/ft of the 2200. Road tests show the 2200 was quicker above 50mph, but significantly thirstier.

        E-series production ended when the Maxi was killed and was replaced with the R-series 1600 for the Maestro. While the South Africans did an R6 2600 for their Rover SDX, there was no need for an R6 in the UK.

    • The Six could have been effective as a 2.4-2.6-litre, if not quite reaching 2.7-litres had the 1797cc 4-cylinder been productionised during development and not considered a potential non-US emissions compliant duplication of the 1.8 B-Series.

      However would it have been worthwhile had a 6-cylinder also been spun-off of the O-Series with a wider capacity range (especially if it appeared earlier on)? Could BMC or BL have justified having two somewhat overlapping sixes based on its two 4-cylinder engines, using a similar rationale to Ford in the US where they created the 2.3 HSC engine because production of the 2.3 Lima was commmited to other models?

      • That was just Ford’s bad management. Why develop a new engine with same capacity and not a lot difference in performance, instead if just increasing capacity in production of the Lima.

        The E series was a missed opportunity. It should have been ready to be lower in emission, and designed to have better performance to replace the whole of BMCs engine range, using Downton to assist in making it powerful. Unfortunately we got Issigonis sticking his bizarre requirements into the mix and it ended up being a bit of a failure, until it became the S series.

        • Would agree to an extent on the basis of its initial sophisticated experimental design (minus Issigonis’s meddlesome requirements and conservative reworking by Bareham/Appleby), potential Downton involvement and the S-Series like features (including 16-valve and diesel schemes).

          It was a missed opportunity in the sense the E-Series could have eventually spawned scaled up (with larger bore pitch plus modular five/six units) and scaled down engines to replace to the entire engine range (ideally by the end of the 70s at the earliest), rather than be a one-size-fits-all replacement out of the box from the late 60s after starting out as a small block 4-cylinder engine design.

          Never knew the HSC was developed due to bad management by Ford. Speaking of the Blue Oval, the CVH despite its bad reputation was an engine that displaced 1.1-2.0-litres (whereas other rivals typically displaced 1.3-2.0-litres if not 1.6-2.0-litres) though find it difficult to imagine Ford considering applying an Opel CiH-like modular approach in creating a larger six to replace their existing sixes. Was it within Ford’s ability to butterfly away the entire CVH episode with an earlier ZVH (maybe 16-valve capable via Schrick?) at minimum or suitable alternative rather than an outright early-80s Zeta in terms of realistic template?

          • The CVH was another disaster! Thr kater Zeta engines were from work that Yamaha did for Ford on multi valves, with the brilliant 1.7 Zetec lump from the Puma showing what could have been done if penny pinching at the blue oval had not been the order of the day on the zeta. By the mid Nineties, Dunton got an influx of new staff to replace what had been tired, who ran with a lot of ideas that never saw the light of day. Did you know they designed a high performance 1.8 turbo diesel than so much torque that it ripped apart the MT575 gearbox from the Cosworth!

          • In addition to being a collaboration between Ford, Yamaha and Mazda did the 1995 Sigma (Zetec-S/SE)’s roots in any way originate from the Zeta as a smaller block replacement for both the Kent and lower-end CVH? Albeit possibly influenced by the K-Series whose secrets Rover were allegedly made to share with Ford during the 1986 negotiations, even if the K-Series was in development at the time and it took Ford years to introduce the Sigma?


      • Ironically BMC Australia developed a 2.4l 6-cylinder B-series in the 60s, so there was a precedent for a 6-cylinder O-series. Component sharing would have given a 2.5 with 124bhp and 145lb/ft, and a 3l with 138-150bhp and 171-180lb/ft.

        Could have made a sensible engine family if they’d chosen 1600/1800/2000cc and 2400/2700/3000cc. But it probably made more sense to reuse the existing Triumph engine manufacturing line, rather than increase production in the Austin/Morris engine plant.

  41. I get the impression that the E6 was overlapping with the smaller Rover SD1s too much & the bonnet could be re-profiled on the Ambassador to just fit the O-series engines.

  42. The 1750 E was a decent enough engine when mated to a five speed transmission. It made the Allegro into a rapid small family car and gave the Maxi the refinement and performance it deserved( the 1500 was too underpowered for the Maxi and was dropped in 1979).

    • Why was the 1500 considered underpowered? After all the replacement Maestro, which was the same size as Maxi, used the 1300 A series for many of its models, which seemed to give acceptable performance.

      • The 1500 didn’t really have much performance – 69bhp with 83 lb of torque at 3200rpm. The 1300 A plus in the Maestro had 68bhp with 75 lb at 3500 rpm from 200c more. I believed the E was slightly heavier. But the E Series was not a performance engine, so it felt slow because of its long stroke and under square design, with the A plus being a very flexible unit with great stronger acceleration. Also the Maxi weighed more than the Maestro, 978kg against 875kg.

      • Originally the weight for what became the Maxi in 99.8 in wheelbase form was anticipated to be about 1004kg, somehow engineers were able reduce the weight of the production Maxi with its 104.8 in wheelbase (via those doors) by some 30kg or so to around 970-978kg.

        In theory a production Maxi with its original 99.8 in wheelbase could have weighed as low as 924kg and that was with a 1.5 E-Series rather than the later Maestro’s 1.3 A-Plus, weight figures for the Maestro 1.6 meanwhile range from 945-975kg depending on the source (and if the unit was an R or S Series).

        • Obviously the 1500 Maxi wasn’t a fast car, but then people didn’t buy them for performance. And I assume it was much faster than the Cambridge/Oxford it partially replaced – 61hp for a car weighing 1,118kg according to Wikipedia!

  43. The Maxi had a heavy body and an early criticism of the car was it was underpowered and needed a bigger engine. My parents had a 1500 Maxi and it was sluggish and not very economical, even with the five speed transmission. The 1500 E was more suited to the Allegro, where the lighter body and five speed transmission gave it decent performance and economy.

  44. My Boss had a Maxi 1750HL company car in the early 70s. I got to drive it a few times and though it wasn’t a car I would aspire to own, it was pretty nippy on the dual carriageway roads out of Newcastle.

  45. I still can’t understand why the E series was developed in the first place. Neither the A nor B series engines were old fashioned or uncompetitive at the time, the 1300 A series was being developed into a competitive production engine while the B series came in 1.6 form which would have been perfect for a car to fit in between ADO16 and ADO17.

    Indeed the money saved on a new engine and factory could have paid for bespoke doors for the Maxi several times over…

    • Not sure about that. A more modern (ohc) was required. I mean, the A and B were both superannuated and couldn’t be expected to serve in perpetuity. Thing is the E wasn’t up to scratch and really shouldn’t have been accepted as originally presented. I’ll admit the A+ was an excellent development of an engine that should have been drawing its pension.

      • The E was compromised by Issigonis, with his strange beliefs and ideas (just look at the DX engine that he came up with. Don’t increase bore size just add more cylinders!). As many have pointed out though, is the original ideas for the E before Issigonis stuck his nose in were more likely to have benefited BMC. And the E series is actually not far off a certain VW engine that powered the company through it’s transition from air cool. In addition the S series which was developed from the E was a good engine, so it had promise. However I still believe the B was capable (a developed Twin Cam anyone?), and as the A+ proved it could cut the mustard in the early 80s, so maybe as Maestrowolf said, those doors could have not been compromised. Though do we think the Maxi would have looked any better!

      • This was the mid 60s though, and most of BMC’s rivals still used OHV engines. Including the Renault 16 which was the Maxi’s nearest rival when launched. Neither the A nor B were old fashioned, if the E had been dropped, the 1.6 and 1.8 B could happily have been used in the Maxi and later Allegro, until a new range of engines was introduced as the O was in the late 70s. Maybe with an end on gearbox.

        The farcical situation developed where a fortune was spent on the E series engine and a new factory, but then the Maxi was saddled with the Landcrab’s doors. And this was compounded by then saddling the Marina with reusing the Morris Minor’s suspension…

    • Both the A and B-Series could have benefited from enough development from the mid/late-1960s to buy the company time to develop suitable replacements for around the late 1970s to early 1980s. That is in contrast to the politicking and differing over how to replace them (all-new vs redesign/upgrade) or to maintain the status quo until the bitter end.

      Would be inclined to agree if the 1.6 was more along the times of the O-Series that shaved some 20kg off the B-Series (if not even lighter to make the E/S-Series 4-cylinder redundant), making it suitable for installation in a midway car between ADO16 and ADO17 if not maybe even ADO16 itself. Could the costs involved in bringing the E-Series into production have been used to update both the A-Series and B-Series on top of providing the Maxi with new doors (if not use ADO16 or the upcoming ADO22)?

      Although there is value in having a midway engine of the original sophisticated E-Series experimental prototype unit that can eventually act as the basis to eventually replace both the A-Series and B-Series, similar to how the Nissan E OHC on top of evolving into the GA was also upscaled into the CA/CD and scaled down into the MA.

      At the same time it was likely the wrong engine to be made into an upward expanding modular design (like using EA111 to create a 5/6-cylinder instead of EA827), when an engine that size would be expanding downwards (e.g. EA111, Suzuki G, ). Especially considering the B-Series descended Project Storm aka 2.5-litre Td5 was envisaged as a 2-litre four and 3-litre six, suggesting it if not an earlier O-Series should have been a modular design.

  46. Issigonis was treated like a tin god by BMC and because he developed the Morris Minor and Mini everything he did was bound to be brilliant. The ADO17 was controversial looking and was an austere car priced closer to Rover territory than the Ford Cortina it was created to challenge, while the Maxi was equally controversial and again lacked the range of trim options fleet markets were demanding by 1969.

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