Initially, the Jaguar XK-150 was offered only as a coupe and convertible, almost as if Jaguar were testing reaction to this obviously fatter cat. When it arrived some nine months later, the roadster was bereft of its cut-away doors, and purists complained. The roadster proved the least popular of the three XK-150 models, accounting for less than a fifth of the total number built.
Besides disc brakes, the XK-150 was notable in being the first postwar Jaguar sports car available with a choice of engine sizes. It was announced with the 210-horsepower version of the 3.4-liter twincam six as used in the XK-140MC. Beginning in the fall of 1959, a bored-out 3,781cc (231-cubic-inch) unit with 20 extra horses was offered as an option, usually teamed with Borg-Warner automatic for the U.S. market.
Following past practice, Jaguar also listed "Special Equipment" 150s powered by "S" versions of each engine, with three huge SU HD.8 carburetors, straight-port head, 9.0:1 compression, and wilder cam timing. The tuned 3.4-liter spun out 250 horsepower at 5,500 rpm, while the 3.8S delivered fully 265 horsepower at 6,000 rpm.
Neither S model was available with automatic, and only discreet badges identified them externally. But just put your foot to the floor and you knew instantly that you were in charge of a special breed of cat. The 3.8S could see the far side of 135 mph with ease, and 0-60 mph was a matter of 7.0 seconds or so with two aboard. Fuel economy, all things considered, was excellent: 18-20 mpg on American highways at the then-legal 70-mph limit. In fact, any of the XK litter would return this kind of mileage given a driver skilled with a manual gearbox.
Even landmark automotive designs must eventually bow to the march of progress (though the Porsche 911 may be an exception), and by 1961 the XK sports car was clearly in need of replacement. Jaguar was ready with the E-type, a machine as stunningly advanced and exciting in its day as the original XK-120 was in the late Forties.
But the E-type would not have been possible had the XK models not succeeded. And succeed they did beyond all expectations. Jaguar built more than 12,000 of the XK-120s, nearly 8,900 of the XK-140s, and a bit more than 7,900 of the XK-150s. Commercial considerations aside, this line is significant because it ushered in one of the most adaptable and long-lived engines in postwar history. It's still going strong more than 35 years later, and even Jaguar's own lovely V-12 and the advent of American emissions standards haven't been able to kill it. That the sports cars it first powered were possessed of a timeless grace and that elegant charm so peculiarly British only adds to their allure. Long counted among the greats, these Jaguars are still captivating enthusiasts, and seem destined to endure far beyond a lesser cat's nine lives.