When the fist thoughts about what would eventually become the MGB began to germinate in the mid-fifties - in the wake of the successful debut of the MGA - common sense suggested that the engine which it would employ would be a development of the B series engine.
The B series , developed out of a 1947 Austin A40 engine, was still relatively new, and although it might not have been either exotic or truly state of art, it was nevertheless proving itself to be reliable, capable and adaptable unit, and as it was assuming a role as a mainstay of the whole BMC family, its future was assured.
As early as 1954 Gerald Palmer, designer of the ZA Magnette and Riley Pathfinder and architect of a series of exciting projects which never saw the light of day, had schemed out his own ideas for a twin cam version of the B series engine. Initially, he saw this primarily as a competition unit. Certainly his first drawings, which show a 90 degree angle between the cylinder heads, a 1489cc capacity and fuel injection are testament to this.
Knowing that an all-new engine challenge the growing European opposition would be unlikely to be sanctioned by BMC, Palmer opted to use the basic B series crankcase with as few alterations as possible. When this new engine was eventually sanctioned, it became slightly larger in capacity and the angle between the heads was reduced to 80 degrees, in the interest of making it more compact; even so, fitting it into the MGA necessitated some careful modifications, amongst them a special access panel schemed by new arrival at Abingdon, Don Hayter.
With the new twin cam engine in production in 1958 (the MGA Twin Cam was launched in July), just about the time that the MGB body-shape was approaching its definitive form, it was seen as most likely that the MGB would feature a 1600cc B series in standard and twin cam forms - at least at launch.
Meanwhile, up at BMC HQ in Longbridge, a flurry of activity was taking place in the engine design department, with much secrecy surrounding a planned range of V4 and V6 engines intended to replace most of the existing mainstream engine ranges with one fell swoop. MG was often employed as a test bed for new ideas, and so it wasn't long before a crate arrived from Longbridge with one of the prototype V4 engines in it.
Under Syd Enever's direction (but without very much enthusiasm on his part, it is said) this engine was shoehorned into an MGA for testing purposes. Immediately, the packaging of the V4 and its planned V6 off-shoot was schemed into the MGB engine bay, and it began to look quite likely that MG would be one of the first off the blocks with the new BMC engines at the start of the sixties.
Fascinating though they were, and in many ways well ahead of their time, the BMC V4 and V6 engines were eventually abandoned (ironically just as Ford's European off-shoots started to move to such units)and so this interesting distraction fell by the wayside.
With production of the big Austin-Healey added to Abingdon's responsibilities in 1957, and thoughts of a common successor to the MGA and Austin-Healey 100/6 taking shape, the men at MG looked at ways of creating a more potent MG, perhaps in the increasingly important two-litre class. Don Hayter recalls a four cylinder unit created by taking the big Austin six and chopping off two cylinders to create a 2-litre four. With growing production volumes, MG thought they might be able to persuade the paymaster at Birmingham to sanction this new engine, but to no avail; Longbridge had other priorities.
In the end, the MGA twin cam engine did not cover itself in glory, and with its discontinuation in 1960, the choice came back to the good ole B series, by now in 1588cc form for the MGA alone. In common with the medium-sized BMC saloons, the MGA in its last versions received a thoroughly reworked version of the B series, now with a 1622cc capacity, and it seemed likely that this would power the MGB as the new car would be called.
Early testing showed up potentially embarrassing problems with the MGB; the performance of the new car seemed likely to be at the best the same as that of the car it was intended to replace, and more probably would be worse. Fortunately plans to expand the B series yet again were already advanced, as the planned big front wheel drive Austin saloon, - ADO17 - would demand a larger capacity engine to provide the performance expected for such a roomy car.
Once again, MG was used as the guinea pig, since the new engine was going to be rejigged for ADO17 with five main bearings instead of three, and consequently the MGB would be the only BMC car to use a 3-bearing 1798cc unit between its launch in 1962 and 1964, when the new 5-bearing units were phased in.
With the MGB safely in production, thoughts of a new engine - other than for the planned MGC variant-were put on the back-burner. Having said that, from 1964 onwards, there were experiments with further stretching the B series to two-litres, and MGB prototypes were run with such engines. By the latter part of the sixties, MG was hoping that they would be allowed to develop a new generation of sports cars, and although the first of these, EX234, might have retained the B series engine, the second more dramatic offering, would have featured the new E series engine which BMC (latterly BL) had developed for the new ADO14 Maxi.
However mergers, cash-flow problems and the onslaught of U.S. legislation (the Clean Air Act of 1963 and the National Highway Safety Traffic Act of 1966) meant that BMC was kept busy coping with the new emissions and safety legislation which began falling into place. As management priorities shifted away from MG towards Triumph, it became necessary to carry out further work to keep the B series engine in production, whilst thinking seriously of a replacement for it.
By 1971, the 2-litre B series engine was resurrected, and before long it metamorphosed through an overhead valve version into the beginnings of what would become the O series. With the launch of the Marina into North America in 1973 (where it was sold as the Austin Marina-other markets having taken it since 1971 as a Morris) the need for the O series engine was seen as more pressing, for great things were expected of both MGB and Marina sales.
There then followed a stop-go period when the O series and the forward MGB program were on and then off again, as various factions within BL jostled for position, and although it had been thought that the O series could have been ready by 1974-75, in the end it would not appear in the home market Marina until 1978, by which time the North American Marina had been dropped ignominiously from Austin-MG dealerships.
By this time, the need for catalyst-equipped cars in California, coupled with the association unleaded fuel, meant that the old B series, well into its dotage, had had to be re-engineered yet again in order to keep the car on sale. This was accomplished not by hardened valve seat inserts but by modifying the composition of the cylinder head material and reducing the sizes of the valves-the latter only serving to weaken performance even more.
As the seventies wore on, work continued with adapting the O series into the MGB-not too difficult a task-and it was planned that eventually both the MGB and the TR7 would share the O series, possibly with higher performance versions being reserved for the Triumph. By the end of the decade, it was foreseen that the MGB would be dropped early in the following decade, and replaced by an MG version of the TR7.
In 1979, of course, BL really kicked the hive, and set the B's buzzing with its announcement that MGB production was to cease, and that the Abingdon factory would be turned over to other use (not closed but emasculated). Within a short space of time, a consortium headed by Alan Curtis of Aston Martin Lagonda pitched in to the battle to save the MGB, and negotiated a deal to continue where BL had effectively left off, building a mildly restyled MGB (basing its design on some of BL's own ideas for a planned 1980-81 facelift) and formulating plans for further developing the car into something new, possibly with a Toyota engine.
As is well known, however, the consortium's bid eventually foundered in 1980, as nervous backers dropped out, and the end of the story for the Abingdon MGB came in October of that year.