The XK140 replaced the XK120 in September 1954. After the immense popularity and success of its predecessor, the XK140 had a lot to live up to. Although the XK140 never recreated the motorsport success of the XK120 because Jaguar were now running the C-type and developing the D-type, the 140 was a commercial success. Don't be fooled by the XK140's less sporty image though; the 140 took everything great about the 120 and built on it.

Although the XK140 retained the same clean, flowing lines of the XK120 there were many improvements to the car hidden underneath. The engine was more powerful as standard, steering was improved by a new rack and pinion system, tighter handling and a smoother rider were achieved by the old leaver arm dampers being replaced by telescopic shock absorbers and the engine was moved forward. Another advantage of the engine moving forward was that more room was created in the cockpit allowing the taller driver far more legroom than in a 120. The roofline of the XK140 was also lengthened to allow room for two tiny rear seats and the screen was moved forward. Full bumpers were fitted and lashings of chrome gave the 140 a more executive look without overwhelming the simple lines of the car.

The XK140 was again available in three body styles; the Open Two Seater (OTS), the Drop Head Coupe (DHC) and the Fixed Head Coupe (FHC). In addition to this, there was a more comprehensive options list. The Special Equipment (SE) option remained with the added option of the 'C-type' head pushing the car's power output up to a claimed 210bhp. The 140 was also offered with an Overdrive and an Automatic gearbox giving the potential customer a full range of options to suit their needs. 

Exports still ruled the day in 1954 therefore, much like the XK120, most XK140s were built in left-hand drive and exported.

Jaguar XK140 production figures

Launched in 1957 the XK150 was the most radical step forward in the XK range since the launch of the revolutionary XK120. The XK150 was vastly different in both style and performance from the XK140 it replaced and was a much bigger step forward than had been taken from the XK120 to the XK140. The most striking change was the straighter wing line, widened bonnet and single wrap-around windscreen, which replaced the now-dated two-piece split screen. This gave the XK150 an altogether more modern look. More generous interior space was also achieved by putting the doors on a diet and the wooden interior was lost in favour of a leather-clad dashboard and door capping.

Although the most obvious changes were the styling the XK150 was also a radical step forward in terms of performance. Most notably disc brakes on all four corners of the car, which had been developed on the C-type with Dunlop, made the XK150 the first of the XK range able to stop as well as it could go. All-round disc brakes on a road car were revolutionary for the time and set the XK150 apart from its competitors. A new cylinder head, the B-type, was added to the 3.4-litre engine producing a claimed 210bhp.

Initially, the XK150 was offered in Drop Head Coupe (DHC) and Fixed Head Coupe (FHC) form however in late 1958 a "Roadster" or Open Two Seater (OTS) variant was introduced. This coincided with the "S" version of the car, initially available only on the OTS but available on the Coupe models from early 1959.

The "S" specification XK150 came with what Jaguar called a "straight port cylinder head"; although the ports aren't actually straight they are straighter and wider than the standard head allowing for better airflow. To keep pace with this increased potential for air/fuel flow triple 2in SU carburettors were added. According to Jaguar, this upped the power to 250bhp.

By this point the power race was truly on, especially in America, so to compete with large-capacity American V8s, Jaguar introduced a new 3.8-litre version of their straight six. In standard form, the new 3.8 was claimed to produce 220bhp and in the "S" specification the power was reported to be 265bhp.

By the end of its production run, there were a huge array of different XK150 models. It was available in DHC, FHC and OTS body styles, in standard specification, SE specification or S specification and with either a 3.4 or 3.8 engine. Although early standard cars were fitted with steel wheels, these are very uncommon now. There are also reports that some early, "standard" specification cars had drum brakes we are yet to see or hear of an XK150 running on drums or having ever run on drums.

In 1961 the XK150 was replaced by the E-type or XKE, a car that was as revolutionary and striking as the original XK120 was in its time. Over its 13-year production run the XK had revolutionised the sports car industry, put Jaguar on the map as a global player in the car market and helped lead the way in helping British industry recover after the war.

Jaguar XK150 production figures