A seminal sports car for both Jaguar and Britain was the XK 120. It used a sedan chassis and a torquey new twincam six that proved an instant classic.

Jaguar XK 120

It’s no exaggeration to say the Jaguar XK 120 helped rejuvenate a nation’s belief in itself. Its seductive shape and magnificent engine brought acclaim -- and orders -- from all continents, reassuring Britons that their beleaguered island still could produce something of international value after World War II’s devastation.

They had William Lyons to thank. Untrained as an engineer or designer, he had what proved an unerring instinct for automotive style and value. A motorcycle enthusiast as a young man, Lyons cofounded the Swallow Sidecar Company in 1921, then moved into automobiles by designing sporty bodies for other maker’s chassis. His breakthrough was the splendid SS 100 (SS for Swallow Sidecar) sports car of 1936.

It wasn’t until after the war that his cars got their own engine, however: a 3.4-liter inline-six with an exotic-for-the-day twincam head and hemispherical combustion chambers. The work of Lyons’s chief engineer, William Heynes, this engine would be Jaguar’s soul into the 1980s. The six was strong and durable because it was intended for use in a sedan due in 1950. But Lyons knew there was greater publicity value in putting it in a new sports car.

Lyons always said he drew the XK 120 with a few quick strokes of the pen, although its basic shape could be seen in an experimental streamlined body he had done for the SS 100 in 1938. Regardless, the XK 120 was a masterwork, a low-slung roadster with pouncing-cat fender lines of disarming grace. Its underpinnings were less exciting: a shortened version of the heavy sedan chassis, independent torsion-bar front suspension, live rear axle, recirculating-ball steering, and drum brakes. No matter. Unveiled late in 1948, the car was an immediate sensation, especially at a price of around $3000.

The Jaguar XK 120's performance rivaled cars costing much more, and though not designed for competition, the XK 120 was a race winner.

Brakes, handling, and engine cooling could have been better, but the XK 120 was comfortable, tractable, and fast -- top speed of 120 mph (hence the car’s name). Early roadster bodies were aluminum, the convertible and coupe that followed were steel, while optional pistons and cams could boost horsepower to 190. In any form, the XK 120 had character and sex appeal and a significance rarely associated with automobiles.

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