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From The Production Line
by Nairn Hindhaugh.
Nairn worked for BMC in the days when the mini was being built and more than likely saw most of our minis come off the production line.
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To get a good idea of the background of the company behind the Mini, there follows some potted histories of BMC and the men who were responsible for this brilliant car. This will be followed at a later date by a story on John Cooper. Here is a brief history of the development of the A-Series engine.
Most of the credit for the birth of the A-Series engine can go to three men, Bill Appleby who was later chief designer of engines and gearboxes at Longbridge, his deputy Eric Bareham, and the original chief designer, Johnnie Rix. In 1942, when the war was still in full swing, Eric laid the preliminary design for a side valve 7hp and this was followed for quite a while until Leonard Lord stipulated that Austin's engines should all employ overhead valves. After all, the 6-cylinder 4-litre truck engine introduced in 1939 used this method, as did the first post war Austin, the Sixteen with its 4 cylinder 2.2 litre unit. The Austin A40, introduced in 1947, used a new ohv 1200 cc engine, (this was later to be modified to become the B-Series), so the new smaller engine was based on the A40's principles.
By July 1949, the dimensions had been worked out for fits and limits, to be about 800 cc, which meant that it would be conventional, in line, and flexible. They wanted an engine which would pull well at low revs, and so a comparatively heavy fly-wheel, large valves and well-researched timing achieved the results they were looking for.
It was decided to use the same stroke/bore ratio as the A40 which is 1.3:1, and the new engine was designed to have 76mm stroke and a bore of 58mm. The head design was carried out by Harry Weslake, using a heart shaped combustion chamber which directed the incoming gas toward the spark plug. This gave improved fuel consumption and more efficient burning compared to the systems used at the time.
As per Austin practice, the camshaft and pushrods were on the same side of the engine as the inlet and exhaust ports. All the electrical equipment including distributor, plugs, starter motor and generator. With both manifolds on the same side, an inlet manifold 'hot-spot' was produced giving good warm-up characteristics. The oil pump was driven from the end of the camshaft, and four rings were used per piston, three compression rings and a lower oil-control ring.
The first engine was assembled in 1950 and when a few had been made, were subjected to rigorous testing. At first it was thought they could use an aluminium head, but resorted to cast-iron to eliminate any problems involved with fitting valve-seat inserts. The crankshaft webs were stiffened in 1951 and the bearing size was increased as well.
In production form, the 803cc engine developed 30 bhp at 4800, so it was clear there was plenty of scope for further development. At its launch, it churned out 75% of the A40's unit, yet it was 33% lighter. The car it was announced in of course, was the Austin A30 in late 1951, and being an ohv unit was in its favour, as Ford would still use side valves for another 8 years in their small cars, and the Morris Minor was also so equipped.
Few would have guessed in 1951 that this engine would be used in so many guises for the next 40 or so years. After the BMC merger, the Minor received this motor and then through a series of improvements and enlargements it would power the Austin A35, A40 Farina, Austin-Healey Sprite, MG Midget, all Minis, 1100s, 1300s, Allegro, Marina (UK) and then in A-Plus form in the Maestro and Montego, Metro and today's Mini and Cooper. Bill Appleby commented years later that perhaps he and his team 'had just about got it right'......
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