engine 73 x 106 x 4 1776 cc May to Nov 1944 XF 75 x 98 x 4 1732 cc Nov 1944 to Jun 1945 XK1 (first of Heynes’ 4 x XJs) 76.25 x 98 x 4 1790 cc Oct 1945 to Nov 1946 XK2 76.25 x 98 x 4 1790 cc Feb to Sep 1946 XK3 76.25 x 98 x 4 1790 cc Dec 1946 to Feb 1947 XK4 76.25 x 98 x 4 1790 cc Nov 1946 to Dec 1947 Gardner Engine (used in record-breaking MG car) 1970 cc 1948 XK Number 1 3-bearing crank 1970 cc 1949-1952 XK Number 2 3-bearing crank 1970 cc 1950-1952 XK 5-bearing crank 1970 cc 1953 By September 1947 a 3.2-litre 6-cylinder version had been produced, called the "XJ 6-cylinder", which was intended to replace both Standard-based 6-cylinder units. Testing showed the need for higher torque at low speeds than this engine could produce and hence it was 'stroked' to 3,442 cc to form the "XK 6-cylinder", which saw its debut in an open two-seat XK120 sports car at the 1948 London Motor Show. Following this the XK6 powered the Jaguar Mark VII and a number of other models in subsequent years. The XG prototype soldiered on as a component testbed until 1948. There also existed an "XK 4-cylinder" of 1,790 cc, also first tested in October 1945 and remaining under development alongside the XK 6-cylinder units. At the time of William Heynes' paper presented to the IMechE in February 1953, the XK 4-cylinder was still referred to as being under development. It was only finally dropped as a possible production engine later in 1953, by which time it had been realised that Jaguar's image in the market had moved beyond the need for a replacement for the old 1.5-litre Standard 4-cylinder unit. Because the 6-cylinder XK prototypes were found to be so much more refined than the 4-cylinder versions, in 1951 a 1,986 cc 6-cylinder version of the XK 6-cylinder was built to see if it would suffice as a smaller scale engine. By 1954 this had grown to 2,483 cc and it was this short-block version of the XK 6-cylinder that was fitted to the new compact Jaguar 2.4-litre (retrospectively known as the Mark 1) released in that year. None of the 4-cylinder prototypes ever advanced to production but Lt. Col. Goldie Gardner's speed record team did fit a 1970