The A Series
Despite the success of the Austin 7 before the war in a large number of markets, Leonard Lord felt that a ‘baby’ car was not as desirable after the war. “He had concluded, he said, that although there should be a new ‘baby’ Austin one day, it could not figure in his top priority”, Robson explains. “This was because he could not guarantee to sell a high enough proportion of such new cars on the export market.”
The big hope in this segment of the market was to be the A40 Devon, powered by a new 1.2lt engine based on but significantly different from that of the A90, alongside the A70 and A90 Atlantic – Lord’s own “Americanised” sports car.
The abject failure of the A90 and the immediate success of the Morris Minor from rival Nuffield were a double blow to Lord, and must have convinced him that he had read the market completely incorrectly.
While Lord’s temper and brashness, to the point of rudeness and beyond, are legendary, one thing to be said in his favour is that he was decisive and once he had elected a path to follow he forced it through with his iron will.
As mentioned in last issue, Lord felt that the future of Austin lay in the company at least doubling in size and after considering all merger possibilities decided that a merger with Nuffield was the most logical and offered the greatest likelihood of success. Talks with William Morris began in 1948 about the sharing of information, if not a complete merge, but when these talks broke down in mid-1949, Lord told Morris that Austin’s would begin work on a direct rival to the Morris Minor.
He then instructed Bill Appleby, head of Austin’s engine design team, to start work on a new engine for an all-new ‘baby’ car to compete with the Morris Minor, that for the time being would be known as the New Austin 7 – with the car to be tackled by Austin’s Chief Designer Johnnie Rix.
The engine design was handled mostly by Appleby’s deputy, and eventual successor, Eric Bareham. The engine was designated AS3 and would eventually, when BMC was formed, be re-designated A-series. However, as this change lay in the future, I will refer to it for its Austin development as the more accurate AS3.
Work on the engine continued a-pace with the design of the new car, with the first prototypes running before the end of 1950 – a remarkably short timeframe, that would be mirrored ten years later with the Mini.
Having the engine ready so quickly is due partly to the fact that Bareham had actually begun design work on paper for a small overhead-valve engine as early as 1942.
The other major contributing factor was that the team involved was the same as that which had already delivered the overhead-valve engines for the A90 and the A40 and that the AS3 engine would be based around already well-established principles.
Britain’s unique RAC Horsepower Rating (see Issue 2) provided a formula for calculating the tax paid on the rated horsepower of engines. This was found to be significantly less effected by changes in the engine stroke, and led to most English engines having narrow bores and long strokes.
Even though the RAC HP Rating had been abandoned at the end of the war, in favour of a flat tax rate, the AS3 followed this line with the same stroke:bore ratio as the A40 engine, at 1.314:1. With a stroke of 76.2mm, or exactly three inches, and a bore of 58mm, this gave a capacity of 803cc.
As Bill Appleby explained in a paper read to the Institution of Mechanical Engineers in 1963; “The engine designed prior to the proposed new one was the 1200cc four-cylinder engine, which had (stroke to bore) ratio of 1.3:1. This engine had been a great success…We could see no point, therefore, in changing this ratio, which was maintained on the new engine.”
Another similarity between the three engines is having the spark plugs and all the electrical ancillaries – distributor, generator, and starter motor – on the opposite side of the engine from the carburettor and exhaust – to avoid any problems that might arise from dripping fuel. It also provided a hot-spot around the manifolds which was considered advantageous to quick warming up. This was found to be somewhat disadvantageous in hotter climates, such as Australia, particularly when used in the later front-wheel-drive cars, and could generate vapour locks in the fuel system.
All three also had the push-rods for the overhead rockers on the opposite side from the spark plugs, which eliminated the need for the push-rods to run inside tubes that could be prone to oil leaks.
This meant there was less space available for porting of the cylinder head, which necessitated siamesed ports – the inlets for cylinders 1 with 2 and 3 with 4, while the exhaust ports for cylinders 2 and 3 were joined. While this was not considered the most desirable for producing power, it was believed, correctly, that it would be sufficient for the use the engine would be put to with the new car.
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