The origins of Jaguar’s most famous powerplant
THE XK engine and the glamorous XK in which it debuted may have first appeared in the optimism of the UK’s first postwar motor show in 1948, but its genesis lay in the dark days of the Blitz.
As engineer Walter Hassan described in his autobiography, by 1943 the Luftwaffe had done its worst for the city of Coventry and the compulsory fire-watching sessions which required Jaguar staff to spend one evening a week on unpaid lookout duty were far quieter than they had previously been.
Never one to waste an opportunity, William Lyons made sure that the potentially tedious fire-watching sessions on a Sunday night were turned into a profitable exercise by ensuring that the team comprised the top technical minds at the company: William Heynes, Claude Baily, Hassan and of course Lyons himself.
Hassan recalled that the team would sign on at 6pm, then settle down to be lectured by Lyons on his plans for the future. In spare moments between the wartime contracts, Lyons had even found time to work up several styling models for the sort of car he wanted the firm to make once hostilities were over and naturally, talk turned to how they would be powered.
At the time, the engines used in the firm’s cars were essentially bought-in designs from Standard, converted to overhead valve operation but Lyons was aware that they were ageing and close to their development ceiling. What was needed was a more modern engine of the company’s own design which would offer more power, improved refinement and potentially greater development potential.
Interestingly, initial development centred around a six-cylinder unit, but the first units to reach the running prototype stage were four-cylinder designs, since the team became concerned at the likely very high rates of taxation in postwar years.
Hassan recalls that in the light of this, consensus was that a 2.4-litre unit would be the largest in common usage, but that Lyons wanted a power output of around 120bhp and was very much taken with the twin camshaft arrangement used by foreign marques like Alfa Romeo.
Both Baily and Hassan countered with the issues of cost and noise generated by a twin cam arrangement and suggested a design using pushrods and overhead valves. As Hassan recalled though, this wouldn’t do: the autocratic Lyons didn’t like the idea and “if he wasn’t completely satisfied with anything he would never agree to it.”
Incredibly, despite the factory being devoted to military work at the time and raw materials very limited in supply, the team managed to build up the first prototypes during the war years, with the Jaguar ‘X’ for Experimental codes being started at this time.
The first f
