Engines : A-Series

The A-series engine did service in a variety of cars for almost 50 years, during which time it was available in a bewildering variety of capacities and states of tune.

A hard act to follow

The 1275cc engine of the MkII Mini-Cooper S.

The 1275cc engine of the MkII Mini-Cooper S.

The A-Series engine was certainly a case of the ‘British Curate’s egg’ – good in places. In fact, that is not quite true: the A-Series was a fine engine. Of course, by the time of the launch of the Austin Metro in 1980, great play was made by the British press about the fact that here they had a new car, which truly competitive and (in the context of the small/medium BL range of cars), as good news as it was, it was still powered by an engine that first saw service in the Austin A30 some 30 years previously. Of course, to make this criticism was to miss the point entirely.

British Leyland had expended much time and effort on the task of replacing the A-Series engine, but the trouble was that it was capable of delivering fantastic fuel consumption figures thanks in no small part to its excellent torque characteristics and thermal efficiency. Because of this, the A-Series became a victim of its own success: why produce a replacement, when there was doubt that anything new that was produced would be any better to drive?

Discounting the remarkable 9X power unit, the first serious attempt to replace the A-Series engine was the anticipated motive power for the ADO74 programme, instigated in 1972. This engine, dubbed the K-Series engine was an OHC design, which had been designed to be canted backwards some 70 degrees in order to improve the packaging of the new car. The signs were promising – and although when bench tested, the power output was significantly higher than the standard A-Series could manage, it still did not produce the same impressive torque figures. Nevertheless, the engine was cancelled, not because it would have proven to be an unworthy successor to the A-Series engine, but simply because it was part of an ambitious development programme that BLMC could ill-afford.

The experimental K-series (left) and A-series (right) OHC engines, now preserved at the Heritage Motor Centre at Gaydon.

The experimental K-series (left) and A-series (right) OHC engines, now preserved at the Heritage Motor Centre at Gaydon.

Signs that the company were becoming keen on developing the (by-now) long in the tooth A-Series engine resurfaced in 1975, when a new OHC cylinder head was produced. The intention was for introduction in the ADO74’s replacement, the ADO88, but there emerged some problems. Like the K-Series before it, this engine produced more power than the older engine, yet did not offer a big enough advantage over it to warrant the expense of a full development programme. Not only that, but following the Ryder Report of 1975, the finances of the company were now controlled by the Government, and as a result, all non-essential spending was placed under minute scrutiny. The decision to call a halt to the A-OHC programme, therefore, was an easy one to make.

From the ashes of A-OHC did emerge the A-Plus programme, which involved a modest upgrading of the engine, which facilitated a small rise in maximum power output (without affecting its torque characteristics) and a lengthening of main service intervals.

As a result, the A-Series engine enjoyed something of an Indian Summer being, as it was, the power unit for the Austin Metro during the whole of the 1980s. It also saw service in the Austin Maestro/Montego and without the disadvantage of the somewhat flawed transmission-in-sump layout; it would prove to be a reliable and strong performer in these cars. Eventually, an engine called K-Series did replace the A-Plus, but it was not the same engine as that from 1972 – and it took a radical change in thinking to produce something significantly better – and this would not arrive until 1989. Had the A-Series not been so eminently suitable for the task in hand – reasonably powerful, economical and compact, the Mini would probably not been the success it was and the Metro would probably never have come into being in the form it did.

The Mini remained A-Series powered all through its life, starting out with just 34bhp in 1959, and ending its days with the 63bhp, twin-point injection unit developed in 1997 by Rover engineer Mike Theaker.

Specifications & applications

Capacity Bore Stroke Max. Power Max. Torque Applications
803cc 58.0mm 76.2mm 28bhp @ 4400rpm 40lb ft @ 2200rpm 1952-56: Austin A30
30bhp @ 4800rpm 40lb ft @ 2400rpm 1952-56: Morris Minor Series II
848cc 62.9mm 68.26mm 33bhp @ 5300rpm 44lb ft @ 2900rpm 1969-80: Mini 850 / Mini City
34bhp @ 5500rpm 44lb ft @ 2900rpm 1959-69: Austin Seven / Austin/Morris Mini
1961-62: Riley Elf / Wolseley Hornet
1964-68: Austin Mini-Moke
948cc 62.9mm 76.2mm 34bhp @ 4750rpm 50lb ft @ 2000rpm 1956-62: Austin A35
1958-61: Austin A40 Farina
37bhp @ 4750rpm 50lb ft @ 2500rpm 1956-62: Morris Minor 1000
37bhp @ 5000rpm 50lb ft @ 2500rpm 1961-62: Austin A40 Farina MkII
43bhp @ 5200rpm 52lb ft @ 3300rpm 1958-61: Austin-Healey Sprite
46bhp @ 5500rpm 53lb ft @ 3000rpm 1961-64: Austin-Healey Sprite MkII
1961-64: MG Midget
970cc 70.6mm 61.91mm 65bhp @ 6500rpm 55lb ft @ 3500rpm 1964-67: Austin/Morris Mini Cooper S
997cc 62.43mm 81.28mm 55bhp @ 6000rpm 54lb ft @ 3600rpm 1961-64: Austin/Morris Mini Cooper
998cc 64.58mm 76.2mm 38bhp @ 5250rpm 52lb ft @ 2700rpm 1962-69: Riley Elf / Wolseley Hornet
1967-80: (Austin/Morris) Mini
1969-75: Mini Clubman
41bhp @ 4850rpm 52lb ft @ 2750rpm 1969-80: Mini Clubman (auto)
55bhp @ 5800rpm 57lb ft @ 3000rpm 1964-69: Austin/Morris Mini Cooper
A+ specification 39bhp @ 4750rpm 52lb ft @ 2000rpm 1980-82: Mini 1000 / City / HL
40bhp @ 5000rpm 50lb ft @ 2500rpm 1982-88: Mini HLE / City E / Mayfair
41bhp @ 5400rpm 51lb ft @ 2700rpm 1980-90: Austin Metro
42bhp @ 5250rpm 58lb ft @ 2600rpm 1988-92: Mini City / Mayfair
44bhp @ 5250rpm 52lb ft @ 3000rpm 1980-82: Austin Allegro
1071cc 70.6mm 68.26mm 70bhp @ 6000rpm 62lb ft @ 4500rpm 1963-64: Austin/Morris Mini Cooper S
1098cc 64.58mm 83.72mm 45bhp @ 5250rpm 55lb ft @ 2900rpm 1975-80: Austin Allegro
45bhp @ 5250rpm 56lb ft @ 2700rpm 1975-80: Mini Clubman
1979-80: Mini 1100 Special
48bhp @ 5100rpm 60lb ft @ 2500rpm 1962-71: Morris 1100 / Morris Minor 1000
1963-74: Austin 1100
49bhp @ 5250rpm 60lb ft @ 2450rpm 1973-75: Austin Allegro
55bhp @ 5500rpm 61lb ft @ 2500rpm 1962-68: MG 1100
1963-67: Vanden Plas Princess 1100
1965-68: Riley Kestrel / Wolseley 1100
56bhp @ 5500rpm 62lb ft @ 3250rpm 1962-64: Austin-Healey Sprite MkII
1962-64: MG Midget
59bhp @ 5750rpm 65lb ft @ 3500rpm 1964-66: Austin-Healey Sprite MkIII
1964-66: MG Midget MkII
1275cc 70.6mm 81.28mm 54bhp @ 5300rpm 65lb ft @ 2550rpm 1974-80: Mini 1275GT
58bhp @ 5250rpm 69lb ft @ 3500rpm 1967: MG 1275 / Riley 1275
1967: Wolseley 1275
1967: Vanden Plas Princess 1275
58bhp @ 5250rpm 69lb ft @ 3000rpm 1967-74: Austin 1300
1967-73: Morris 1300
1967-68: MG 1300 / Wolseley 1300
1967-68: Riley Kestrel 1300
1967-68: Vanden Plas Princess 1300
59bhp @ 5300rpm 65lb ft @ 2550rpm 1969-74: Mini 1275GT
59bhp @ 5300rpm 69lb ft @ 3000rpm 1973-80: Austin Allegro
60bhp @ 5250rpm 69lb ft @ 2500rpm 1968-71: Austin America (auto)
1971-80: Morris Marina
65bhp @ 5750rpm 71lb ft @ 3000rpm 1968: MG 1300 / Riley Kestrel 1300
1968-73: Wolseley 1300*
1968-74: Vanden Plas Princess 1300*
* Automatic models retained 58bhp unit (see above)
65bhp @ 6000rpm 72lb ft @ 3000rpm 1966-74: MG Midget MkIII
1966-70: Austin-Healey Sprite MkIV
1971: Austin Sprite
70bhp @ 6000rpm 74lb ft @ 3250rpm 1969-74: Austin 1300GT
1969-71: Morris 1300GT
70bhp @ 6000rpm 77lb ft @ 3000rpm 1968-73: MG 1300 MkII
1968-69: Riley Kestrel 1300 / Riley 1300
76bhp @ 5800rpm 79lb ft @ 3000rpm 1964-71: (Austin/Morris) Mini Cooper S
A+ specification 50bhp @ 5000rpm 66lb ft @ 2600rpm 1992-2000: Mini Sprite / Mayfair
61bhp @ 5550rpm 61lb ft @ 3000rpm 1990-91: Mini Cooper
61bhp @ 5300rpm 69lb ft @ 2950rpm 1980-84: Morris Ital
62bhp @ 5600rpm 72lb ft @ 3200rpm 1980-82: Austin Allegro
63bhp @ 5700rpm 70lb ft @ 3900rpm 1991-1996: Mini Cooper 1.3i / Cabriolet
63bhp @ 5500rpm 70lb ft @ 3000rpm 1997-2000: Mini Cooper 1.3i (TPi)
63bhp @ 5650rpm 72lb ft @ 3100rpm 1980-90: Austin Metro
64bhp @ 5500rpm 73lb ft @ 3500rpm 1983-85: Austin Maestro HLE
68bhp @ 5800rpm 75lb ft @ 3500rpm 1983-93: Austin Maestro
68bhp @ 5600rpm 75lb ft @ 3500rpm 1984-89: Austin Montego
72bhp @ 6000rpm 73lb ft @ 4000rpm 1982-89: MG Metro
73bhp @ 6000rpm 73lb ft @ 4000rpm 1989-90: Metro GTa
77bhp @ 5800rpm 80lb ft @ 3000rpm 1991-2000: Mini Cooper S 1.3i
78bhp @ 6000rpm 78lb ft @ 3250rpm 1990-91: Mini Cooper S
93bhp @ 6130rpm 85lb ft @ 2650rpm 1983-89: MG Metro Turbo
96bhp @ 6130rpm 1989-90: Mini ERA Turbo

John Cooper Garages

During the 1990s Mini Cooper revival, John Cooper Garages offered a number of factory-approved “Cooper S” and “Cooper Si” upgrades to the standard Coopers. The conversions came with a full Rover warranty, and could initially be fitted by any franchised Rover dealer.

Type Max. Power Type Max. Power
S pack (carb.) 77bhp 3rd Si pack (SPi) 86bhp
1st Si pack (SPi) 77bhp 1997 Si pack (TPi) 85bhp @ 5500rpm
2nd Si pack (SPi) 82bhp 1999 Si pack (TPi) 90bhp @ 6000rpm


Cutaway drawing of the 848cc A-series complete with transmission-in-sump, as it first appeared in the 1959 Mini.

Cutaway drawing of the 848cc A-series complete with transmission-in-sump, as it first appeared in the 1959 Mini.

The 998cc Mini-Cooper engine, in situ.

The 998cc Mini-Cooper engine, in situ.

The A-Plus version of the A-series engine laid bare. The revised engine represented an investment of £30m, and would see service in the Mini, Allegro, Ital, Maestro and Montego, as well as the Metro for which it was originally developed.

The A-Plus version of the A-series engine laid bare. The revised engine represented an investment of £30m, and would see service in the Mini, Allegro, Ital, Maestro and Montego, as well as the Metro for which it was originally developed.

Cutaway drawing of the A-series with end-on gearbox, as used in the Austin-Healey Sprite and MG Midget from 1961 until 1974.

Cutaway drawing of the A-series with end-on gearbox, as used in the Austin-Healey Sprite and MG Midget from 1961 until 1974.

The longitudinally-mounted, 948cc A-series, as fitted to the MkI MG Midget.

The longitudinally-mounted, 948cc A-series, as fitted to the MkI MG Midget.

The OHC A-Series engine, as produced by BL Technology: The engine is one of only four OHC A-series engines built by BL Technology during the 1970s, one of the others is in Gaydon (Pictured at the top of the page). The head is aluminium with 36.5mm inlet and 30mm exhaust valves.

The OHC A-Series engine, as produced by BL Technology: The engine is one of only four OHC A-series engines built by BL Technology during the 1970s, one of the others is in Gaydon (Pictured at the top of the page). The head is aluminium with 36.5mm inlet and 30mm exhaust valves.

A-OHC Picture supplied by Ian Nicholls – car owned by Jerry Evans

Keith Adams

About the Author:

Created www.austin-rover.co.uk in 2001 and watched it steadily grow into AROnline. Is the Editor of Classic Car Weekly, and has contributed to various motoring titles including Octane, Evo, Honest John, CAR magazine, Autocar, Diesel Car, Practical Performance Car, Performance French Car, Car Mechanics, Jaguar World Monthly, Classic Car Weekly, MG Enthusiast, Modern MINI, Practical Classics, Fifth Gear Website, and the the Motoring Independent... Likes 'conditionally challenged' motors and taking them on unfeasable adventures all across Europe.

44 Comments on "Engines : A-Series"

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  1. Models Blog | 4 July 2016
  1. Greg Botes says:

    hi guys I have a cooper and I live in South Africa, the car was also assenbled in SA
    my problem is I am tyring to fined out what the number off the engine wound of been. the chasse is of a Cooper so would it be posable to get the number for the motor that would have gone the car? its a long shot.

    Thaks guys any help would be great.
    Regards Greg

  2. Francois LaGrandeur says:

    We are currently restoring a 1977 Mini 1000 Saloon Canadian edition, with a 998 cc engine. What are the technical specifications, compression ratio, horsepower and torque?

  3. Nate says:

    Apparently in Mini: The Definitive History by Jon Pressnell, 475cc 2-cylinder (along with a seperate 500cc 2-cylinder two-stoke) prototype of the A-Series was also developed that was effectively half of a 948cc A-Series, running under the code ADO11 prior to its cancelation.

    The existence of a prototype 2-cylinder A-Series is quite fascinating and its a pity there was not enough money to develop the idea further.



  4. Zach says:

    Hi there, i have a 1984 classic austinmini mayfair with a 998 engine in it, i was wondering if it is possible to fit a turbocharge or a supercharge kit on it, any help or links would be much appreciated.

  5. francis brett francis brett says:

    @4 you can put the cylinder head from a I4 BMW motorbike on if you wanted to push the boat out,direct fit,16 valve ohc.Allyou would need to do is convert to belt drive -kits available.Supercharging is popular,and the book “Tuning BL’sA series” by David Vizard will prove invaluable.

  6. Chris Baglin says:

    @5 Francis Brett,

    Are they reliable, and how much power can you extract from a BMWised A Series?

    Isn’t a limiting factor of an A Series the fact that it has only 3 main bearings?

  7. Will M says:

    What could a Mini clutch handle, in terms of BHP?
    (I assume it could be upgraded to one from a 114GTa)

  8. francis brett francis brett says:

    @6 Of course this isnt a off the shelf option,attention to the bottom end is required-balancing,lightening etc,well over 100 BHP on a 1300+ can be obtained,but you have to build in the reliability,just look at the Triumph 1300-1500 engines-three bearing crank very strong although it does have a desaxe crank configuration.

  9. Ian Nicholls says:

    I have a 1293 cc Mini that pokes out 103 bhp at 5800 rpm.
    It has a stage 3 head , Swiftune SW5 cam , high lift rockers , twin SU 1.5 carbs , Maniflow exhaust and is lightened and balanced . It is so reliable it went to Switzerland and back in 2011. I had it built by TMW engineering who build engines for the Mini Seven and Miglia series.
    My own view is to stick with traditional tuning.
    BMW K heads have rubber belts. If they snap in the middle of nowhere , you are in trouble.
    7 and 8 port heads are only worthwhile above 6000 rpm and only work properly with fuel injection which adds about a grand. Front mounted carbs would probably result in icing.
    Supercharging – avoid at all costs !
    I went for the carb set up and suffered from chronic carb icing.It produced 140 bhp , but was very unstable and kept blowing head gaskets .

  10. Zach says:

    any useful links for kits and/or somewhere i could buy a motorbike engine?

  11. Tom says:

    @zach have a look over at http://www.turbominis.co.uk/
    plenty of them have turbocharged 998cc a-series blocks. some/most of the parts can be sourced from the metro turbo or era turbo and most small turbo can be used from different cars. Im using a saab 93 turbo.

  12. John Ruffle says:

    “Isn’t a limiting factor of an A Series the fact that it has only 3 main bearings?” It’s still good for 8000 rpm with a Cooper “S” or similar steel crankshaft and flywheel. The engine is amazingly durable set-up right. Ford used the 5-bearing crankshaft as its USP when the Cortina was head to head with the BMC 1100. Interesting that Ford (and others)have reverted to cart axles on the rear of their small cars. I do wonder how a trusty “A” series compares with a new-fangled 3-cylinder beast… strip off all the electronic engine management and what have you got left??? BMC “A” Series…. loved if for no other reason than she was my “first love” lol!

  13. Chris says:

    Just wondering if you have any more information on the a-ohc engine and the mini owned by jerry evans. I know the cars current owner and am very intrested in knowing more about the engines history.



  14. jerry evans says:

    What do you need to know about the ohc engine? I built it.


  15. Fausto Maia says:

    please inform if you have used angines reconditioned or not
    for classic MINIS 1300 cc or 1400 cc.
    Please send pictures and prices

  16. Franklin Woodcock says:

    I have got a 1275cc Marina engine and box in my Marlin Roadster. If I wanted to prepare a replacement engine I would want the “youngest” A+ I could find. This would appear to be from a late Maestro, say 1996. My query is this – the Maestro had a VW gearbox, would it be possible to take the engine backplate off the A+ and put my Marina plate on so I could keep the original box?

  17. Rodney Duggua says:

    My Austin 1300 GT has been fitted with an A+ engine by a previous owner, I’m guessing this is either the 62/63 bhp version? Other than buy David Vizard’s book is there an available source for tuning data? With thanks.

  18. Keith Adams Keith Adams says:

    Do you already have Vizard’s book and need more information?

  19. John Sneddon says:

    Does any one have a complete lsiting of the A series engine identification codes. I am trying to identify the following “2nd Group Gearbox & Ancilliaries” codes:
    As well trying to establish the meaning of “Z” when applied to the “3rd Group” as defined in various BMC Parts Lists.
    Any assistance would be very much appreciated.

  20. Andy Smith says:

    hi i have a 1275cc a series no 12H908AA 123229 any one know what year it is thanks

  21. I was one of the three engineers who designed the H and K-Series engines mentioned above at Longbridge in 1971. The other two were John Rowe (who designed the crankcases and auxiliaries) and Dick Spray who mainly designed the crankshaft, conn-rods and pistons. I designed the cylinder head and valve gear and top-end auxiliaries (distributor and fuel pump drives etc) and also the pressed steel sump and stubby little plastic dip-stick.

    The photo of the ‘K-Series’ is incorrectly titled. It is a 1,000cc H-Series. How can I tell? The cylinders are perpendicular to the sump face. On the K-Series, the cylinders were canted back by 15 degrees.

    The photo also has a banner title reading “1972 K-Series OHC Engine”. That too is incorrect, It shows a 1972 H-Series OHC Engine.

    As a matter of interest, the entire H series engine was installed with the sump mating face canted backwards by 20 degrees.

    For this reason, when installed in the vehicle, the H-Series cylinders were canted back 20 degrees and the K-Series cylinders were canted back a total of 35 degrees.

    This brings me to correct the text above the ‘K’ Series photo at the top of the article. It incorrectly says the cylinders of the K-Series were canted back 70 degrees. Er….I don’t think so. They’d be close to horizontal if that was the case.

    The K Series was the result of Harry Webster moving the H-Series’ goalposts. The H-Series was to be a ‘dedicated’ engine of 1,000cc only with no future-proof features built in to allow later engineers to increase its capacity.

    Then Webster decreed that he wanted an engine that would provide a 900cc and an 1,100cc capacity. This was for ADO74 and was the engine with the cylinders canted back 35 degrees as installed.

    I have never read anywhere of a second K-Series engine version. This was again the result of a Harry Webster directive. Now he wanted the K-Series to be of just one capacity; 1,300 cc. This engine was certainly designed and may even have been prototype built and tested. I cannot recall this because by then I’d joined Stan Johnson’s Advanced Engine Design section in the Roundhouse.

    Another feature of all these engine designs was their ‘inside-out’ clutches with the plate mounted between the flywheel and the cylinder block. Unlike the A and B-Series transverse engines, whose aluminium flywheel/clutch covers were stressed by the forces exerted by the clutch slave cylinder, those on this new family didn’t even need a clutch cover. In fact, John designed a thin plastic cover held with three plastic turnbuckle fixings (as on the ADO 16’s front engine water shield). And this cover was only needed to stop a mechanic’s tie getting caught in the clutch!

    As a lifelong motorcyclist, I can tell you that the inspiration for the overall engine concept was a typical Japanese four cylinder motorcycle engine (such as the Honda 750-4) where removal of the lower crankcase reveals the crankshaft and all the gear-shafts laid out across the bottom of the engine for easy servicing.

  22. I omitted to say for the record that the A-Series OHC cylinder head conversion shown above was designed by my colleague Mike Ward and was a sister design to the H/K Series top end. I also recall that Mike had a beautiful wife and drove a beautiful MGB GT.

    The L-Series (never heard of that one?) was a B-Series OHC design very similar to the A-Series OHC. It was designed by Mike Mills.

    Another mystery Longbridge engine. How about the F-Series? A chain-driven SOHC 1,500cc engine with off-set slanted valves operated by a camshaft with slipper followers. The F-Series designer was Charles Maries.

    And of course, many of the O-Series cylinder head features came from the H/K Series engines.

    All of these engines were being designed and tested while I worked in Petrol Engine Designs in the early 1970s. What a pity that the company’s dire management meant there was never enough money to mass-produce more than just the O-Series in that time.

    And by the way, the original O-Series was a modern 2 litre design that was stymied by Harry Webster’s insistence that it should use the B-Series crankshaft. The crankshaft is the heart of any engine design. It dictates the cylinder pitch (bore centres) whether there is enough room to have coolant passages between the bores and the maximum rpm of the engine (determined by its stroke). And using the B-Series crank meant dumping the O-Series’ original five bearing crankshaft too.

    The reason for the B-Series crank was that the company had just paid for a brand new transfer machine in East Works to machine B-Series cranks. So Harry Webster’s edict was that any new engine of 1500-2000 litre capacity MUST use a B-Series crankshaft! How did the production engineers sign off a new expensive machine for such an obsolete crankshaft knowing that a new engine (the O-Series) was on the stocks?

    Again, for the record, the O-Series was designed mainly by Clive Repton, Dick Spray, Trevor Hadley and Terry Gottlieb. Others, such as myself and Jeff Bishop were seconded for weekend overtime to hit its crazy deadlines.

  23. Richard16378 says:

    Thanks for the information about the BMC / BL engines Ray.

    It’s interesting that the B-series had some important tooling renewed so late on, when some B-series patterns were being padded out with cigarette papers to keep them in shape.

  24. Spyder says:

    Reading this article made me wonder what were the greatest British car engines-not necessarily those with the best design or greatest output but the ones that made the biggest overall impact in British cars.

    1- BMC A-Series
    2- Ford Kent
    3- Rover/Buick V8
    4- Ford Essex V6
    5- Ford Pinto
    6- BMC B-Series
    7- Jaguar XK
    8- Rolls Royce V8
    9- GM Family I
    10=Rover K-Series
    10= GM Family II

    Whilst I realise that some of these engines were not designed or even built in the UK they all had a huge influence on British built cars

  25. christopher storey says:

    Well, the impact of the RR V8 was that it demonstrated that a large capacity engine could be made of alloy and be light . In that sense it is a forerunner of the Buick/Rover, which of course was only half the capacity . As far as the rest of the list is concerned, I would hardly say that the Pinto was of any consequence, nor the GM family engines , and I am a bit pushed to think what the impact of the Essex V6 was , other than being used in a series of kit cars : it was nothing like as good an engine as its straight 6 predecessor, and most certainly was not one of Ford’s best efforts

  26. MGBmarvel MGBmarvel says:

    If anyone is still reading this thread and wants to identify and A or A+ series engine Guessworks has an engine decoder on his website

  27. Clive Horridge says:

    We had a 1071 engine in a mini we prepared for small 12-car club rallies and with the stage II head and cam, it was an amazing engine! One thing that I thought I remembered was that it was a 5 bearing crank for the cooper S and the MG midget, but none of the write ups mention a 5 bearing crank. Have I dreamed this bit? If it wasn’t a 5 bearing crank, were the main journals wider than the standard A series?
    Thanks in anticipation of responses.

  28. Nate says:

    Probably opening a can of worms here though curious to know why (aside from the usual financial problems, shelved replacements, etc) road-going production versions of the 1293-1380cc A-Series were never considered?

    Some bring up concerns about reliability, drivability and engine life whereas others say that the 1293-1380cc A-Series will be no less reliable, drivable or compromised in terms of engine life then any other A-Series unit.

  29. Talk of the Rover 3.5 V8 reminds me of a couple of Marina (ADO28) projects I undertook. The development engineer involved with both these projects was ‘young’ Jeff Johnson (not to be confused with the ex-BRM ‘old’ Geoff D Johnson, the Chief Petrol Engine Engineer at the same time).

    There was an idea circulating to rally the Marina and we looked (on paper) at various ways of boosting its performance. One was to turbocharge the B-Series 1.8 engine. Such an engine was built using a Holset H1 turbo which at that time was the smallest turbo in production (although it was really too big and would only ever give a ‘high match’). Holset were based in Huddersfield I seem to recall and they were quite excited by the prospect when we first went up to meet them. Then I discovered that the Rover V8 was actually LIGHTER and produced double the power of the B-Series 1.8. That was a big surprise. I have a feint memory of young Jeff Johnson building a V-8 Marina in the development shop. I wasn’t involved with this.
    The second project I recall was the design and building of a dry-sump B-Series engine for use in the Marina. I cannot recall the prompt for such an idea (it wasn’t my own idea) – probably some sporting use I guess. Rather than reduce power by fitting a huge oil pump, I designed a system using inlet manifold depression (vacuum if your like) to suck the oil out of the sump into a remote metal oil tank which in turn, fed oil to the regular pump. I took a steel pickup pipe (about 50mm dia) from the bottom of the regular tin sump up through the side of the sump at an oblique angle and thence into the space alongside the engine where it was brazed into the bottom of a metal radiator header tank. A rubber pipe from the inlet manifold connected onto the normal overflow outlet pipe in the tank’s filler neck which was capped by an non-pressure cap (as you’d expect).
    With a theoretical 14.7 lb/in2 pressure availbe to move the oil out of the sump, this system worked really well but I don’t recall it ever being used in anger. Maybe on the test bed.
    And before I drop off my perch, is there space here to recall the ‘3 litre’ Maxi?
    This had two Maxi engines – the regular manual transmission engine up front and an automatic unit at the rear. Mini experience of double-engines (its capacity was 2,550cc altogether) taught the lesson that the driver couldn’t manage two gearboxes so he used the front gearbox and the rear engine just sorted itself out regarding gear selection.
    These projects were again handled by the boys downstairs (relative to we designers in the Engineering block next to the Kremlin) in the development department overlooking the Lickey Road.
    There’s still more. Around 1973 I designed a simple device to convert the E-6 engine into a variable capacity design. A 1.1 litre 3 cylinder unit for speeds up to 50mph (and sipping fuel at an incredible 50mpg) with the full 2.2 litre 6 cylinders available automatically for better acceleration and speeds over 50mph. Anybody could make this device in the garden shed today and it worked so well that nobody knew when it went from 3 to 6 cylinders. In fact I had to fit a dash-panel lamp to indicate when it was on 6 cylinders.

  30. Nate says:

    In retrospect, what would have been the most effective way for BMC to both update the A-Series engine as well as potentially reduce costs had the capital been available to realise such a project?

    Without any direct A-Series replacements entering the equation, would say a die-cast all-alloy version of the Second Generation South African 970-1275cc A-series engine sharing the same 70.6 mm bore with OHC, 5-bearing crankshaft and 8-port head have been a useful update?

    Such an engine would inevitably entail discontinuing the 848cc A-Series OHV used in the Mini 850 / City with the 970cc A-Series OHC serving as the entry-level unit or instead be potentially replaced by a production 9X Mini engine of around 750-900cc (up to if necessary 1000cc) for Mini/Metro-sized cars.

    • Ray Battersby says:


      To answer your question about the South African engine being used to replace the A-Series, it will help if you first understand the political/financial climate in which engines were designed at Longbridge in the early 1970s.

      In the early 1970s, we were told that the tooling costs for a brand new engine was of the order of £45m – far more than BL could afford at that time. By comparison, the A and B Series were produced on a shoestring budget using knackered old tooling that was replaced at relatively low cost, piece-meal as and when required…

      The company’s paucity explains why we fiddled around designing modern OHC cylinder heads to fit to these old engines. Once a ‘cheap’ modern OHC design had been found, it was sound logic to try to extend the life of the old engines by given them a scintilla of modernity.

      Lack of cash also explains why completely new designs (O-Series for example) were invariably crippled from conception by dictating their use of an existing major component to save the tooling costs of a new item.

      A case in point was the stipulation that the O-Series must use the B-Series crankshaft.

      Modern engines have much shorter strokes (thereby larger pistons) than equivalent engines designed in the 1940s. They use bigger pistons (which increases the distance between each cylinder bore) and they invariably use five main bearings instead of the old-fashioned three bearing designs.

      Incorporating the B-Series crank in the O-Series meant that within a millimetre or so, the bore and stroke of the new engine would be the same as the B-Series, the engine being cast aside in favour of a more modern design! Moreover, continuing to use an expensive forged steel crankshaft (as used in A and B-Series) added unnecessary costs to the new engine that would have been perfectly happy to perform using a cheaper cast iron crankshaft.

      The original 2 litre O-Series design, unfettered by such strictures, was a ‘square’ engine of 86mm bore and stroke. Each cylinder was fully surrounded by cooling water (no ‘siamesed’ bores); it used a cast iron five bearing crankshaft. This crankshaft provided the shorter stroke to revolve at a higher speed (and speed means power) whilst providing the space within its larger bore to accommodate the bigger valves that would support such higher speeds. This short-stroke block was longer (due to bigger pistons) but less tall than the B-Series allowing it to fit beneath the fashionably low-bonnet-lines of the Design Studio’s latest concepts.

      But the O-Series was stymied the day that Harry Webster ruled that it must incorporate the B-Series crankshaft. This instruction was based on the fact that BL didn’t want to scrap the new tooling they had just purchased for this crankshaft. From that moment, the O-Series became little more than a B-Series OHC conversion.

      But who had signed off the new expensive tooling knowing the B-Series was being replaced by the O-Series? As stupid a decision as replacing the roof of a house scheduled to be demolished.

      So to answer your question regarding the South African engine; I don’t think BL would have been interested in copying this engine because of the new tooling costs required. And this is regardless of how well the design performed in the areas of size, weight, manufacturing costs and the usual measures of engine performance (power, fuel consumption and emissions).

      Personally, I don’t recall this engine design (though I remember the ‘South African Mini’ that was sometimes mentioned when A-Series modifications were made). What exactly were its features and design specification?

      • Nate says:

        Ray Battersby

        Thanks for answering my questions and providing context.

        From what I have been able to read on the Second Generation South African A-series engine, it featured an oil filter mounted high on the block, new internal oil galleries and an integral block casting that did away with the removable tappet covers.

        Engines were produced in two sizes, 1098cc (or more accurately 1097cc) and 1275cc. However, unlike the engines produced in the UK, the South African engines shared a common bore, of 70.64mm, and the displacement was altered by the stroke, meaning only the crankshaft and pistons would not be interchangeable between the two yet the same connecting rods were retained – 1098cc was achieved with a stroke of 69.85mm (compared to the long-stroke 1098cc engine found elsewhere), while 1275cc came courtesy of an 81.28mm stroke.

        It caught my interest mainly because the A-OHC project on the surface at least appears to feature similar displacements and elements to the Second Generation South African A-Series including a common 70.6 mm bore.

        By the way curious to know whether Eddie Maher’s improvements to the A-Series was simply limited to an All-Alloy Head (or whether it was a Crossflow, 8 Port head and something more) as well as whether any connection exists between Eddie Maher’s tuned A-Series and the MG-badged Victoria prototype with a tuned, twin-carb (83 bhp) version of the 1275cc engine?


  31. Ray Battersby says:


    Whilst writing, may I respond to your earlier question about the 1293/1380 A-Series?

    Reliability of these engines would most certainly be reduced (all other things being equal).

    Let’s talk crankshaft. If you envisage looking along the length of a crankshaft you can possibly imagine the circular outlines of the main and big-end bearings. A modern, short-stroke crankshaft will use larger bearing diameters than the A-Series and looking along its length, the bearings actually overlap each other. This adds tremendous strength and durability to the crankshaft and also reduces its tendency to bend (and ultimately break) when it is supported by only three main bearings. An old style crank (such as the A-Series), with its smaller bearings and longer stroke is the opposite with no overlap whatsoever.

    So when the A-Series is ‘stroked’, it exacerbates this issue by reducing the overlap of the main and big-end bearings. This is not a good move to make for any engine, especially when the crank is already made of forged steel!

    Turning to the cylinder bores. From memory, the A-Series was originally designed as an 803cc capacity. In this mode, I am sure that the water passages within the cylinder block extended completely around all four cylinders. As its bore was increased over the following decades, water flow was reduced and I seem to recall that nota single cylinder of the 1275cc block had water flow completely around any of the cylinders. I have read people who say that siamesed bores are good for strength. Quite possibly but how do humans warm their hands on a cold winter’s day? We rub our hands vigorously together to create frictional heat that is absorbed by the hands.

    A siamesed cylinder is no different except that we don’t want to warm up the pistons of adjacent cylinders! That leads to piston and cylinder distortion, oil passing the ring pack into the combustion chamber and potential seizures. siamesed bores also leave little room for the cylinder head gasket to completely seal adjacent cylinders. In the 1970s, 6mm of metal between adjacent cylinders was the absolute minimum for a gasket to seal. A leaking head gasket (between cylinders) completely ruins the performance of both cylinders – 50% of the total engine.

    So unless a cylinder block has been designed to be bored out, the end result can only reduce reliability.

    When Harry Webster first announced the H-Series engine specification to the drawing office in 1970-71, he named it the ‘dedicated’ engine. Why?

    He recognised that most of the costs of solving A-Series problems had resulted from repeatedly increasing the 803’s bore and stroke over the years. He wanted the new H-Series to be dedicated to 1,000cc and we thus ensured that it could neither be bored nor stroked without manufacturing a completely new engine. We allowed just a 3mm clearance between the conn-rods and the crankcase as they swept around inside. There was simply no room to increase the cylinder bores because, much against our better judgement, all the bores were already siamesed with just 6mm between them.

    • Nate says:

      Ray Battersby

      So a 1293/1380cc A-Series would not be worth developing compared to the existing 1275cc A-Series, let alone a theoretical 1390cc E4.

      How did the dedicated H-Series perform in Mini-sized prototypes compared with the 1275 A-Series beyond the goal for the H-Series to produce 60 BHP per litre?

      • Ray Battersby says:


        Stresses in rotating/reciprocating parts tend to increase as the cube of their speed. Doubling their speed results in 2^3 (2 x 2 x 2) = 8 times the stress. Add 10% to the speed and stress increases by 1.1 x 1.1 x 1.1 = 33% stress increase. You can do anything as long as you don’t over-stress the materials you are using at their normal working temperature so your 1390cc E4(for example) MAY be perfectly OK if you use better quality materials and/or reduce engine speed. For example reducing engine speed alone by 10% would reduce the component stress by 27%.

        The two SA ‘A’ Series engines are unusual in using identical cylinder block and conn-rods. The more usual methodology would use identical crankshafts and con-rods whilst the blocks would be identical overall apart from the cylinder diameters. Thus the major difference is the two piston diameters. The method you describe will also create a top-heavy piston for the small-capacity unit that could create excessive piston canting.

        Concerning the predicted road performance of the H-Series, I do not posses any actual road test figures from a Mini but believe that I have the computer predictions of acceleration and maximum speed though I expect this would have been based on the weight and aerodynamics of the ADO72 not the Mini. These predictions are not to hand but I will try to look them up and publish the performance data.

        • Nate says:


          Look forward to seeing the computer prediction figures from the H-Series (and related K-Series) engine for ADO74, would be interesting to see how it compares with the A-Series and other A-Series replacements / updates.

          The 1390cc E4 in this case would feature both a bore and stroke of 76.2 mm.

  32. Nate,
    Since there appears to be no PM facilities, could I ask you to contact me via my website (www.teamsuzuki.co.uk)?

  33. Ian Baker says:

    Hi there, usual stupid talk about cars in the pub Monday evening led to subject of frogeye sprites. my friend had one bought for his then girlfriend in late 1960s. I had one in 1972 until ’74, which was bought as a non runner with seized clutch and totally I rebuilt it during the summer, fitted with, I think a 1098cc engine. the next one I bought in 1976 needed much work, and was fitted with twin webers, and the engine was worn. I rebuilt the car, much welding needed, done by a friend, and put it back to original spec with 950cc engine. this blew up quite spectacularly one night, and the workshop that built the engine agreed to replace it. this is where my memory fails me. I am certain the engine capacity was an odd one, and rather think it was that used for a mini cooper, but I remember it ran to 6,000rpm, and redlined at 6,500. never did take it above 6,000 though. I retained the twin webers-are they 40DCOE ?-and it was very loud indeed with much intake noise. I sold it for 3 times what I paid in 1980 when I went to the USA. Now the point of discussion in the pub was exactly what size engine it had, and was it 3 bearing or 5 bearing crankshaft. As far as I know they were all 3 bearing, so I assume my friend was talking b*ll*cks as per usual!
    Any ideas on what spec engine the frogeye would have fitted with would be gratefully received if only to get my friend Colin to keep quiet until his brain is working.
    Enjoyed the discussion very much, and reminiscences of engineers gave much insight into BMC/British Leyland management philosophy.
    I used to deliver parts to factories near Oxford at one time and remember the utterly shambolic organization at the plants.
    Ian Baker

  34. Graham Hill says:

    Interesting to see that OHC again. I found 3 of these in a warehouse in 1989 ish, two of which I think went to Japan, and the third I built up, made the dcoe manifold and had running in an ordinary 78 mini which we showed at some mini show in the Midlands that year. I remember a chap walking past and casually telling his mate it was a Maxi engine! I can’t remember the name of the guy who bought it from me, but I think he had a Patrick Motors clubman that he was going to put it in. More news would be good!

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