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

Gallery

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:

AROnlineholic between 2001 and 2014 - editor of Classic Car Weekly, and all round car nut...

20 Comments on "Engines : A-Series"

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  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.

    http://i555.photobucket.com/albums/jj470/mab01uk/2-cylinder-a-series.jpg

    http://i555.photobucket.com/albums/jj470/mab01uk/2-cyl.jpg

  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.

    Thanks,

    Chris

  14. jerry evans says:

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

    Jerry

  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:
    860
    883
    889
    902
    905
    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

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