A J B Flat–four

Power without glory

He didn’t have the resources of Coventry-Climax, but a former military engineer by the name of Archie Butterworth proved able to make a unit of such high specific output that it should have rivalled the best. Keith Howard tells a story of enterprise

The past is a foreign country, so LP Hartley famously observed. To appreciate just how foreign and how differently they do things there, you have only to reel back half a century to grand prix racing of the early 1950s. In stark contrast to today’s megabuck closed shop, it was still possible then for amateur racers to mix it with the professionals and for tiny companies to build cars in which those enthusiasts could compete. It was even feasible, if you had the skill and determination, to build almost single-handedly a racing engine fit for grand prix service.

One man who did exactly that was Archie Butterworth. A colourful character of the old school — who, among his other achievements, shot for England and was instrumental in founding the British Sporting Rifle Club — Archie had no formal training in engineering but displayed a natural aptitude for it. In 1940, as part of the British Expeditionary Force retreating to Dunkirk, he decided German machine-guns were far superior to the British Army’s and cobbled together the materials to begin drawing something superior. As a result he was given a post at Enfield following his evacuation and was later moved to Chobham to work on tank design.

At the end of hostilities, determined to be his own boss, he formed Butterworth Engineering Co, based in Grove Gardens, Frimley, near Farnborough. His first racing special, S1, had been a dirt-track car built before World War II. Now he set about assembling the astonishing four-wheel drive S2. Like Sidney Allard, Archie had seen the potential in the Steyr air-cooled V8 that had been widely used by the German Army to power everything from staff cars to half-tracks. As Archie recalls today “it was only a glorified truck engine”, but he managed to increase its output from the standard 85bhp to about 260.

This prodigious power and the traction advantage offered by its unique 4WD system made S2 a formidable competitor in straight-line sprints. Archie also hill-climbed it, but he was dearly better designing engines and transmissions than he was chassis, so it proved a handful around bends. It cornered better left than it did right, which may help explain a big accident at Shelsley Walsh in 1951 in which Archie was seriously injured. He was in Worcester Infirmary for three weeks as a result, at the outset of which it was uncertain he would survive.

Although he never formally retired from racing, Archie’s driving career ended there. S2 was bought by the Four Wheel Drive Corporation of America, shipped to the US and campaigned by Bill Milliken, one of the co-authors of Race Car Vehicle Dynamics, a modem classic on the subject. Perhaps driving the S2 helped inspire Milliken’s interest in vehicle handling.

Archie turned his attention instead to the development of a flat-four racing engine of his own design which would feature an invention he had patented in 1949 — the swing valve. Reasoning that a conventional poppet valve will always impede gas flow even when the tulip is lifted clear of the valve seat, Archie conceived an inlet valve which swung out of the way, almost like a opening door. The head of the valve was conventional but its stem was curved to meet a pivot point behind and to one side of the inlet port, giving it an overall shape reminiscent of a French horn. Splined to a bearing shaft at its upper end, the valve was closed by three thin torsion bars, disposed in an equilateral triangle around the axis of the bearing rod and joining its far end to a fixing in the cylinder head. Valve actuation was via a single camshaft per bank, operating rockers that engaged with the stem of the (conventional) exhaust valve and short pushrods that opened the swing valve. The arc of the latter’s movement was about 40 degrees, so that when fully open, its face was at right angles to the cylinder walls.

Ignition was by twin Lucas magnetos and fuelling by original pattern Amal motorcycle carburettors, one per cylinder, with integral slide throttles. Although the carburettor bodies are visible in the photograph, the top-exit throttle cables and the arms that operated them are missing.

Capacities of 1.5, 2 and 2.4 litres were envisaged, the engine initially being built in ‘interim’ form as a 1984cc unit (87.5mm bore, 82.5mm stroke) using conventional inlet valves, while the swing valve was still in development. This was the engine Bill Aston and Robin Montgomerie-Charrington raced in the Aston-Butterworths, without great success during 1952 and ’53, although the car was lying seventh at Spa in 1952 until it was replenished with the wrong fuel. Another interim engine was sold to Kieft, and one or two more to other privateers.

Greater success came in 1957 when, in 1.5-litre form and with the swing valves now incorporated, the engine was fitted to the Elva MkiII driven by Archie Scott-Brown. While it stayed together, the fully-fledged AJB was notably powerful — Butterworth measured 148bhp at 6200rpm, a specific output of almost 100bhp per litre, on the dynamometer given him by Bill Aston — but it had a propensity for dropping valves. It wasn’t the novel swing valve that caused problems but the sodium-filled exhausts, whose heads were wont to detach and fly out the tailpipe.

Despite repeated appeals from Elva’s founder Frank Nichols to change this aspect of the design, Archie refused. The inevitable result was that Sabrina’s AJB (the car was so nicknamed because its two very prominent bonnet bulges surrounding the inlet pipes gave it a passing resemblance to a well-endowed starlet) was eventually replaced with a Coventry-Climax.

Archie Butterworth wasn’t so concerned with the success of his engine by then because he hoped to make his fortune from another invention, the Sidler, which allowed a car to be swung sideways into a parking space little greater than its length. It was a forlorn hope. Apparently Alec Issigonis, among others, admired it but the investment was never forthcoming to put it into production.

Archie doesn’t recall exactly how many engines he made but it was probably fewer than a dozen. As his interest turned to target shooting, the AJB flat-four and its swing valve passed into obscurity.

Thanks to Roger Dunbar of Elva Racing Components