Just a Short Story - An Engine for the Masses

The A-Series engine under the microscope.

2y ago

The A-Series engine powered the majority of small British cars in its fascinating life and, with production spanning from 1951 to 2000, it was truly a brilliant piece of design.

The A-Series - 1951 to 1980


The original A-Series engines were of a tiny capacity, one of which being the 803cc. This engine produced a tiny 28bhp, whilst being fed by a small 'H2' S.U. carburettor. It wasn't powerful, but it marked the start of great things to come.


In 1956, the British Motor Corporation saw fit to increase the displacement of their baby engine to 948cc. The larger capacity was achieved by enlarging the bore of the old 803cc from 2.3 inches to 2.48 inches. Power output increased as a result with some engines producing up to 46bhp.


Now, we move on to one of the more commonly known A-Series engines; the 848cc or '850' that was developed, at least at first, for the famous Mini. It was essentially a 948cc with the piston stroke dropped from 3 inches to 2.687 inches in order to lower the capacity to 848cc. The reason for the change was simply that, in 1959, the Mini's designers felt the 948cc made the new car too sporty.


The 997cc deserves a high place on this list as it is, in all honesty, one of the rarest engines in the A-Series line up. It was released in 1961 and only ever fitted to 1 model of car; the very first Mini Cooper. Badged as the Austin Seven Cooper and the Morris Mini Cooper, the engine produced 55bhp. The new output owed its existence largely to a revised bore size and piston stroke. This was the first time an A-Series was fitted with twin HS2 S.U. carburettors as standard, with an improved cylinder head aiding gas flow.


The 998cc was released in 1962, originally developed for the Wolseley Hornet and Riley Elf due to the need for a slightly more powerful engine to propel the extra luxury crammed in the Mini frame. It eventually found its way in to a number of cars including the revised Mini Cooper in around 1963.


In 1962, a demand for a bigger engine for larger B.M.C. saloons was apparent; the result was the 1098cc. It was, in essence, a 998cc that was stroked to the larger capacity; from 3 inches to 3.296 inches. This was the engine that powered the famous B.M.C. '1100' vehicles in the '60s and '70s, with around 55bhp.


The 1071cc was another interesting powerhouse. It was developed solely for the very first Mini Cooper 'S' and was essentially a Cooper Formula Junior racing engine that was shoe-horned in to create a competitive race and rally car. The bore was 2.78 inches whilst the stroke was 2.687 inches; the same as the 848cc. This new engine was the most powerful A-Series yet designed, developing 70bhp.


Yet another one off engine, the 970cc was again developed for the Mini Cooper 'S'. This time it was purely to meet homologation for the 1 litre class in motorsport. The lower capacity was achieved by shortening the stroke of the 1071cc whilst keeping the bore size the same. There was a small issue, however; the power was now down 5bhp to 65bhp. The benefit was that this engine could rev quite phenomenally high, though and it was that which kept it competitive in motorsport.


This is arguably the most famous of all the A-Series engines and the most powerful as standard. It was fitted to endless British cars in the '60s and '70s until it went out of production in 1980 before being replaced. In the tiny frame of the Mini Cooper 'S', it produced 75bhp whilst being fed by twin HS2 S.U. carburettors.

The A-Plus - 1980 to 2000

1980 saw the majority of engine capacities in the lineup dropped; all that remained was the 998cc and 1275cc. The main changes to them being: stronger blocks and cranks, lighter pistons and upgraded piston rings, although some will tell you that the older versions are superior, including me!

998cc +

The 998cc + was fitted to several cars from 1980 to 1992, the last of which being the Mini City and Mini Mayfair in which it produced 42bhp.

1275cc +

Here is where things start to get interesting. It was in the lifetime of the 1275cc + engine that fuel injection and turbocharging began to get chucked into the old design. The ordinary version of this engine produced between 50bhp and 77bhp, depending on which model it was fitted to but, in 1983, it was fitted to the MG Metro Turbo. This was the first time an A-Series engine was turbocharged and was largely to keep up with the ever increasing 'hot-hatch' market emerging in the 1980s. It was fitted with a Garrett T3 turbocharger, a modified S.U. carburettor and weirdly, no intercooler, meaning that the power varied significantly dependant on weather. That said, they usually produced around 94bhp which was enough to give the majority of hot-hatches a shock in the '80s. The turbo was dropped in around 1990 but in 1991, fuel injection was added. Originally a single-point-injection system, it was upgraded in 1997 to multi-point-injection which ultimately allowed the engine to run smoother and more efficiently.

The end of an era

2000 saw the last Mini roll off the production line and with it, the last A-Series engine. It was a 1275cc A+ in a Rover Mini Cooper Sportspack, developing 63bhp from its multi-point-injection system. 49 years had come to a halt with the advent of new, more powerful and efficient engines and technologies that saw the A-Series as completely obsolete. I think it's a shame; I love the A-Series. What do you think?

Thanks for reading!

As always, thanks for reading and please let me know what you think in the comments. I love to hear back from you all!

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Comments (5)

  • Good old British engineering. Bet you didn't know the K series rover engine was still being used in the new MG 6

      2 years ago
    • I didn’t know that! I’m guessing it’s got a different name now?

        2 years ago
    • It was in the October edition of classic car buyer. I thought it had died when MG Rover went under. Plus the K series engine was used in other cars across the world not just Rovers.

        2 years ago
  • It had a good run. Well written mate.

      2 years ago
  • Proper good engine

      1 year ago