During World War II, engineers at the company which would soon change its name from SS to Jaguar worked on the design of a new engine. Known as the XK, this six-cylinder unit would for a long time be the only one Jaguar used, and even after others had been introduced it would remain in production for four decades. Here is its story.
Before the XK
In the SS days, the company used engines of between 1.5 and 3.5 litres provided by Standard, a then successful manufacturer which fizzled out in the 1960s. The SS100 pictured above was one example. Other Standard-engined models designed in the 1930s continued to be sold as Jaguars after the war.
The first production Jaguar to use the engine was the sensational XK120 sports car. It was greeted with amazement at the 1948 Earls Court motor show and went into full-scale production in 1950 with a steel body rather than the aluminium one used for the prototypes.
The Mark VII
At this stage Jaguar wasn’t really interest in sports cars. The XK120 was a showcase for the engine, which was intended for the Mark VII saloon launched in 1951. This luxury car was remarkably inexpensive, handled very well and could exceed 100mph. It was also surprisingly successful in motorsport, and won the Monte Carlo Rally in 1956.
The competition version of the XK120, with a completely new body and chassis, was officially called the XK120C and became known as the C-Type. It won the Le Mans 24 Hour race at its first attempt in 1951, and repeated the feat two years later.
Jaguar redesigned the XK120 and put the new version, called the XK140 (pictured), on sale in 1954. It was replaced three years later by the XK150, which remained in production until it was superseded by the E-Type in 1961.
The next racing sports car after the C-Type was, logically enough, called the D-Type. Jaguar won Le Mans with it in 1955 and then temporarily retired from competition, leaving the Edinburgh-based Ecurie Ecosse team to take victory in 1956 and 1957. In early cars the XK engine was used in the original 3.4-litre form, but its capacity was increased to 3.8 litres and then, due to a rule change, reduced to 3.0.
The XKSS was the road-going version of the D-Type intended mostly for the US market. Jaguar planned to sell 25 examples, but only 16 left the factory before a disastrous fire in 1957. Forty years later, Jaguar completed the production run, putting nine brand new cars on sale at over £1 million each, well over the original price of $6,900.
Several companies used the XK engine to power their own sports racing cars. One of the most successful was Cambridge-based Lister. Lister-Jaguars won many races, often in the hands of the severely disabled but exceptionally talented Archie Scott-Brown. The new Lister company built started building replica models, including a Sir Stirling Moss Special Edition, in 2014.
Portuguese-born John Tojeiro was another British constructor of racing cars. Four of these, all exceptionally good-looking, used Jaguar engines. In a 1985 interview published in Motor Sport magazine, Tojeiro said, “The Lister was clearly the best of the Jaguar-engined specials, but I like to think my cars were the best of the rest.”
The Mark 2
Built between 1959 and 1967, this was the most successful Jaguar of its time. Like its predecessor, retrospectively known as the Mark 1, it used the XK engine not only in its usual 3.4-litre form but also as a 2.4-litre. Mark 2s were also available as 3.8s.
The E-Type has been regarded as one of the most beautiful cars ever made since the day it was launched in 1961. Most examples had 3.8- or 4.2-litre XK engines. From 1971 it was offered with a 5.3-litre V12, originally intended for racing and only the second Jaguar engine ever designed.
From 1964, 4.2 litres became the most common size for the XK engine. One Jaguar to use it was the 420G, originally called the Mark X and, confusingly, not the same car as the smaller 420 of that period. The 420G was discontinued in 1970, by which time a far more popular Jaguar had arrived on the scene.
The XJ6 was launched in 1968 and at first used only the XK engine, though the V12 was added in 1972. The 1987 XJ6 was the last Jaguar-badged production car to use the XK unit.
From 1972 until 1981, Surrey-based Panther built a car called the J72. Similar in appearance to the pre-War SS100, it used Jaguar mechanicals. 3.8- and 4.2-litre XK engines were available, along with the V12. Both engines were also fitted to the extravagant Panther De Ville.
The end of the XK
Apart from very low-volume ‘continuation’ models such as the 2017 XKSS mentioned earlier, the last production car to use the XK engine was the Daimler DS420 limousine, manufactured from 1968 to 1992. Based on an extended 420G platform, it had a very large eight-seater body and the 4.2-litre version of the XK. Although not practical for everyday use, it was bought by wedding companies, governments and several royal families including the British one. With special bodywork, it was also used a hearse.