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HAPPY 50th BIRTHDAY XK - in June, 1998 (CMM 111) we paid tribute to one of the greatest sportscars of all time. Peter Cahill tells the story of the Jaguar XK120.


1939 TO 1945 WAS ALTOGETHER a different period in the history of the British Motor Industry; many vehicle manufacturers were engaged in work totally divorced from their mainline bread and butter. Others had successfully negotiated contracts with the Ministry of Defence that would 'keep their foot in the door', producing tank engines, armoured cars, trucks, ambulances, staff cars, trailers, even sidecars. The trick was to get an MoD order large enough to justify a certain amount of development work.

One manufacturer introduced a passenger car range in 1947 using an engine never previously released before, but developed during the war, originally intended for a jeep that never saw the light of day. The Austin Sheerline and Devon saloons launched in Sept 1947 had first been sighted in the 'verboten' area at Longbridge, in full size model form, during 1943. With very few exceptions, most of the industry was engaged in similar actions, anticipating the cessation of hostilities and confident in an Allied victory. Jaguar were no exception.

The Company had discussed the possibility of designing and building their own engine during 1939 but temporarily shelved the project, with the outbreak of war. Long hours of fire watching duty, at Jaguar, during the continuous threat of enemy air raids on Coventry encouraged the 'night shift design team' of Jaguar boss William Lyons, chief engineer Bill Heynes, engine specialist Claude Baily andThe Jaguar XK120 - the cat's whiskers! later Wally Hassan to spend their time profitably forward planning for the better days to come. Engine development and a new engine in particular was a regular item on the agenda.

Walter Hassan's arrival at the Coventry factory, in 1944, following six years at the Bristol Aeroplane Company, was more than a coincidence. Whilst at Bristol, Hassan, a man with an established reputation as the 'hands on' designer and builder of many famous and successful pre '39 racing cars, had concentrated on carburettor and induction system design. As Jaguar's Chief Experimental Engineer his influence and application, based on his wide experience, would be considerable, not only in engine design and development, but also with chassis and chassis related systems. In years to come between his two terms of Jaguar service he would mark his presence at Coventry Climax as the linchpin in their success as 'formula' engine designers and manufacturers.


During 1946 the new engine project re-surfaced, with serious intent. With it surfaced the Jaguar 'X' prefix denoting an experimental project. XG represented a design for a twin cam based on an existing Standard Motor Co block, using the BMW cross-over pushrod design. To hell with patents, who were the war winners?

Williams Lyons had given the engineers his engine specification simply and direct - it was to have smooth power and be aesthetically acceptable - when the bonnet was lifted it should reveal an attractive looking engine. The required effect was achieved on both counts, in the latter - on first sight the impression was of a metallic piece of nouveau art, a base of solid dark cast iron topped by the angular beauty of the rectangular polished cam boxes. Whilst the principle and layout had been used in racing cars and in aviation this was the first time that a twin overhead camshaft hemispherical head engine had been put into normal series high volume production. XF, a 2 litre four cylinder unit was used for combustion chamber, valve and valve gear design and development. At this point in time, XJ, had nothing to do with a range of cars, it was the first six cylinder prototype unit, of just over 3 litre capacity. 3.4 litre(3,442cc) was eventually adopted as the capacity of the 160 bhp production six. Some said that at 3.4 it had a better low speed performance that its lower capacity cousin. Others said that the availability of inexpensive second hand cylinder block boring machines, ex Standard Motor Co - just across the city from Jaguar, which came complete with tooling for 83mm cylinder bores was also a contributory factor.

Some manufacturers post war would rely on up-dated models of their pre-40 ranges. Our quartet of eminent automotive firewatchers were well aware of the competition that would face them in a recovering market and they were aware of the need to maintain and increase their place in the saloon car sector worldwide -then the core sector of Jaguar's business. While priority was given to the design of a new saloon powered by the new engine, a revised pre war chassis with independent front suspension was introduced as an interim measure..

1948 and the Earls Court Motor Show would see Jaguar launch their new Mk V Saloon utilising a new torsionally stiffer chassis incorporating the Citroën inspired wishbone torsion bar suspension. William Lyons was 'Master of his own Manor', highly respected by his work force and when in the weeks immediately prior to the Motor Show he reasoned that Jaguar at Earls Court could do with an additional new attraction on the stand, to liven up the proceedings, no body questioned his decision.

Bill Heynes, Wally Hassan and the team, took just three weeks to construct the new Jaguar 120 Aluminium Super Sports (its original designation) prototype on a shortened MkV derived chassis - out of the limelight, in Fred Gardner's (Saw Mill Superintendent) woodshop, a part of the factory known and recognised as a totally independent principality and kingdom. William Lyons played his traditional role as body designer the now famous 120 line finally interpreted by the ash body frame panelled in aluminium. Oddly, neither Lyons nor his management anticipated any real demand for the car such that his design for the body was free and without commercial restraint, without reference to the car becoming a series volume produced model. This prototype in turn spawned a further six hand built pre-production cars, with panels supplied by local Foleshill specialists Abbey Panels. Just over two hundred and forty cars t were similarly clothed in aluminium bodies. The steel shelled cars that followed were built on the same line interspersed with MkV saloons, in the 'Manchester' shop, a reference to the factory area used to produce wartime aircraft fuselage and wing assemblies, a part of the old White and Poppe factory in Swallow Lane Holbrooks. Prophetically, management of the day little realised that the large pieces of Whitley bomber built here, flown from a city airfield site in the Coventry district of Whitley would in later years be the site and home of Jaguar's current Engineering, Research and Development Centre.

The first issue of the 120 sales brochure referred to the availability of the XK 100, the four cylinder option originally intended as the fuel economy conscious home market car. William Lyons had road tested a '100' engined car just prior to the Show. Labelling the engine as rough and obviously unimpressed he killed the engine at that point, in spite of the considerable factory stock of components awaiting assembly.

The 120 took Earls Court and the World, by storm, priced at £998, or the then equivalent of $4000, it was unbelievable value for money. It maintained William Lyons's practice, throughout, of having a low volume sporting car in the range - closely priced to the saloons.

To counter early scepticism evident in some quarters, not least the media, about the achievable 120 mph claim, Jaguar works test driver Ron 'Soapy' Sutton, hammered the new car down a closed section of the Belgium Jabbeke Highway at the officially timed speed of 126.8 mph with a production windscreen, hood and sidescreens erected and 132mph with an aero screen and tonneau cover, returning past the assembled journalist at 10mph , in top gear, to demonstrate the car's flexibility. The 3,4 double overhead cam six was producing as much power as the 5.4 litre V8 of the day, built by Cadillac. All of this prior to the car going into regular production served only to wet the appetites of the motoring public still more.

Many of the early aluminium bodied cars found their way, not unnaturally, in to competitions no doubt encouraged by six examples that were, for publicity purposes, works-prepared and 'allocated' to well known competition drivers of the day Leslie Johnson, Nick Haines, Peter Walker, Clemente Biondetti, Tommy Wisdom and Ian Appleyard. The latter of course was William Lyons's son-in-law who amongst many wins, won the Tulip Rally in 1951 and was outright winner of the Alpine Rally in 1950,1951 and 1952. The equally attractive fixed coupe version of the 120 was announced in March 1951 and in August 1952 a works-prepared car pounded the Paris circuit of Linas-Montlhery for seven days and nights, driven by Moss, Fairman, Johnson and Hadley. Averaging 100mph for the 168On the track - the big cat at play hours the team substantially breaking 8 world records and covering over 16,800 miles (27,000kms)

The range was eventually completed with the introduction of a very attractive drop-head coupé combining creature comforts of the fixed head with the fresh air appeal of the original roadster

12,000 cars and five years later, when XK120 production ceased, the car had broken more world records, and had wiped the board in international, national and club racing, rallying and hillclimbing - worldwide. In its C type form it had convincingly conquered the World's most prestigious endurance race - the 1951 Les Vingt Quatre Heures du Mans.

The XK 120 was significant not only because of its sporting elegance, its high standards of refinement and comfort, but also because it introduced into the history of the automobile one of the most successful engines ever. A design and engineering concept developed and still evident in the Jaguar production engine last fitted in a Series 3 XJ6 as late as 1986 and supplied in the last of the prestigious D420 Daimler Limousines in 1992.

Records show that the car was most popular in its purist, original roadster form as the XK120, from 1948 to 1954. Of the three variants totaling 12,078 cars, the open version accounted for 7,631 units 2,678 fixed head coupes and drop heads 1,769. Diminishing numbers were recorded for the XK140 (total 8,884), XK150 (total 7,929), XK150S from 1958 to 1960 (total 1,466). From 7,631 XK120 Open units, not including drophead coupes, the follow- on 140 open version accounted for less than 50% of its 120 forerunner at 3347. The XK140 and the XK150 were never intended or developed for competition although close examination of Jaguar competition records show that both the 140 and 150s, to their credit, were winning races plus class wins in rallying in 1960, both in Europe and North America.

At the Earls Court Show back in 1948, the first post-war motor show, it was intended that the new MKV saloon would be Jaguars 'star of the show', but that was not to be. The sports car, the XK120, so quickly conceived in Fred Gardner's wood shop confounded the experts and proved to be the makings of yet another of the many Jaguar legends. The car's popularity has never waned, to the contrary, the public still view it in total awe whenever it appears.

Peter Cahill

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Most recent revision 12 August 1999 13:52:18 GMT - Copyright © 1996-2003 CMM Publications. Illustrations by ©Dave Iddon. All Rights Reserved.