Jaguar · 1948–1954

Jaguar XK120

The Jaguar XK120 is a sports car manufactured by Jaguar between 1948 and 1954. It was Jaguar's first sports car since SS 100 production ended in 1939. The XK120 was launched in open two-seater or (US) roadster form at the 1948 London Motor Show as a testbed and show car for the new Jaguar XK engine designed by Jaguar Chief Engineer William Heynes. The sports car caused a sensation, which persuaded Jaguar founder and Chairman William Lyons to put it into production. The fastest production car in the world in its time, it would go on to be developed into the XK140 and XK150 models.

Text from Wikipedia (CC BY-SA 4.0).

Predecessor: SS Jaguar 100 · Successor: Jaguar XK140

All Jaguar XK120 data: UK builds, safety, recalls, model years →

History

Beginning in 1948, the first 242 cars were wood-framed open 2-seater bodies with aluminium panels. Production switched to the 1cwt or 112 lb (51 kg) heavier all-steel in early 1950. The "120" in the name referred to the aluminium car's 120 miles per hour (190 km/h) top speed (faster with the windscreen removed), which made it the world's fastest production car at the time of its launch. In 1949, the first production car, chassis number 670003, was delivered to Clark Gable. The XK120 was ultimately available in three body styles, all two-seaters and available either as Left (LHD) or Right Hand Drive (RHD): an open 2-seater described in the US market as a roadster (OTS); a fixed head coupé (FHC) from 1951; and a drophead coupé (DHC) from 1953. Certain Special Equipment roadster and fixed-head coupé cars were produced and sold between 1948 and 1949 as an early production run for enthusiasts, denoted by an 'S' preceding the chassis number. A version with a smaller engine (2-litre 4-cylinder) designated the XK100 and intended for the UK market was cancelled prior to production. On 30 May 1949, on the empty Ostend-Jabbeke motorway in Belgium, a prototype XK120 timed by the officials of the Royal Automobile Club of Belgium achieved an average of runs in opposing directions of 132.6 mph (213.4 km/h) with the windscreen replaced by just one small aero screen and a catalogued alternative top gear ratio, and 135 mph (217 km/h) with a passenger-side tonneau cover in place. In 1950 and 1951, at Autodrome de Linas-Montlhéry, a banked oval track in France, open XK120s averaged over 100 mph (160 km/h) for 24 hours and over 130 mph (210 km/h) for an hour. In 1952 a fixed-head coupé took numerous world records for speed and distance when it averaged 100 mph for a week. XK120s were also

Construction

The first 242 production XK120s, hand-built with aluminium bodies on ash framing, were constructed between late 1948 and early 1950. To meet demand, and beginning with the 1950 model year, all subsequent XK120s were mass-produced with pressed-steel bodies. Aluminium doors, bonnet, and boot lid were retained. The DHC and FHC versions, more luxuriously appointed than the constantly exposed open cars, had wind-up windows and wood veneers on the dashboard and interior door caps. The XK120’s steel chassis was mostly copied from the Jaguar Mark V, using many of the same parts. The dual overhead-cam 3.4 L straight-6 XK engine was highly advanced for a mass-produced unit of the time, featuring a high-temperature, high-strength aluminum alloy cylinder head, hemispherical combustion chambers, inclined valves, and twin side-draft SU carburetors. Using 80 octane fuel a standard 8:1 compression ratio developed 160 bhp (119 kW). Most of the early cars were exported; a 7:1 low-compression version, with commensurately reduced performance, was reserved for the UK market, where the post-war austerity measures then in force restricted buyers to 70 octane "Pool petrol". The Jaguar factory's access to 80 octane fuel allowed it to provide cars with the higher compression ratio to the press, enabling journalists to test the model's optimum performance in Belgium, on a long, straight stretch of road between Jabbeke and Ostend. The XK engine's basic design by William Heynes, later modified into 3.8 and 4.2-litre versions, survived until 1992. All XK120s had independent Heynes designed torsion bar front suspension, semi-elliptic leaf springs at the rear, recirculating ball steering, telescopically adjustable steering column, and all-round 12-inch drum brakes which were prone to fade. Some cars

Engine specifications

== Performance == The Motor magazine road-tested an XK120 in November 1949. This pre-production car, chassis number 660001, road-registered as HKV 455, was the first prototype built. It was also the 1948 London Motor Show display model, and had been driven by Prince Bira in the 1949 Silverstone Production Car Race. When tested, it had the 8:1 compression ratio, was fitted with an aerodynamic undertray, and ran with hood and sidescreens in place. The magazine reported a top speed of 124.6 mph (200.5 km/h), acceleration from 0–60 mph (97 km/h) in 10.0 seconds and fuel consumption of 19.8 miles per imperial gallon (14.3 L/100 km; 16.5 mpg‑US). The car as tested cost £1263 including taxes. The XK120 M for US market accelerated from 0–60 mph (97 km/h) in 8.7 seconds, top speed was 132 mph (212 km/h) by the speedometer, but actual top speed was about 120 mph (193 km/h).

Racing and rallying

XK120s were active in racing and rallying: 1949. First race victory: In the Daily Express-sponsored One-Hour Production Car Race held on 30 August 1949 at Silverstone Circuit, England, Leslie Johnson drove the Jabbeke car to the XK120's first-ever race victory (despite an early collision with a spinning Jowett Javelin which dropped the Jaguar to fifth). The car, road-registered HKV 500, was converted to right-hand drive for Silverstone. Two other XK120s took part. One, driven by Peter Walker, finished second and the other, driven by Prince Bira, spun out of contention when a tyre punctured. 1950. First victory in America: In January 1950 Johnson also scored the model's first competition success in America, winning the production class in a race at Palm Beach Shores, Florida with the car that had finished second at Silverstone. The Jaguar lost its brakes but finished fourth overall. John Lea, Jaguar's Experimental Department mechanic who attended the race, reported: "The conditions at Palm Beach were wet, windy and sandy. Water and sand gained entry into the brake drums at the front, and the mixture had the effect of accelerating the wear very considerably. Our car finished with no linings and with the steel shoes bearing on the brake drums." Pebble Beach Cup: In May, XK120s driven by Phil Hill and Don Parkinson finished first and second in this event at the inaugural Pebble Beach Road Races in 1950. In 1950 Jaguar allocated six alloy-bodied XK120s to drivers Leslie Johnson, Peter Walker, Nick Haines, Clemente Biondetti, Ian Appleyard and Tommy Wisdom. Le Mans: Three of the allocated cars, mildly modified, entered the 1950 Le Mans 24 Hours race. Johnson, who spearheaded this factory-supported assault on the race with co-driver Bert Hadley, never ran lower than seventh p

High-speed runs and records

=== 1949 === 132.596 mph (213.393 km/h) through the flying mile: in May, Jaguar demonstrated an XK120 to the press on the high-speed autoroute between Jabbeke and Aalter in Belgium. The road was closed for the occasion. The white left-hand drive car, chassis number 670002, was the second XK120 built. Jaguar's development engineer Walter Hassan was to have driven but fell ill, so Jaguar test-driver Ron "Soapy" Sutton substituted. With hood and sidescreens erected, and the airflow under the car improved by the addition of a full-length aluminium undertray, the Jaguar was timed through the flying mile by the Royal Automobile Club of Belgium at 126.448 mph (203.498 km/h). With hood, sidescreens and windscreen removed, a metal airflow deflector fitted in front of the driver, and a tonneau cover fastened over the passenger side of the cockpit the speed improved to 132.596 mph (213.393 km/h). The Observer's Book of Automobiles said it was the fastest production car in the world. The Special Equipment 'S' series cars made in 1948-1949 had better compression ratios and were capable of top speeds of 128 mph. 1950. 107.46 mph (172.94 km/h) for 24 hours (including stops for fuel and tyres): Leslie Johnson sharing his XK120 JWK 651 with Stirling Moss at the Autodrome de Montlhéry, a steeply banked oval track near Paris. The first time a production car had averaged over 100 mph (160.93 km/h) for 24 hours. Changing drivers every three hours, the Jaguar covered 2579.16 miles, with a best lap of 126.2 mph (203.10 km/h). 1951. 131.83 mi (212.16 km) for one hour: Johnson solo in JWK 651 at Montlhéry. "No mean feat...driving at almost twice today's maximum (UK) speed limit into a steep turn, assaulted by the G-Force induced by 30 degree banking twice every minute, using Forties technology,

Production

== XK100 development == A 2-litre four-cylinder version of the twin cam XK engine was to have powered an XK100 variant of the XK120 for the UK market. Details of the model were included in an "Advance Particulars" brochure for the XK but Jaguar's managers were dissatisfied with the engine and the project was cancelled prior to production.

Sections adapted from Wikipedia (CC BY-SA 4.0); text is shortened. Read the full article for the complete history and citations.

Specifications

name: Jaguar XK120
Manufacturer: Jaguar Cars
Production: 1948–1954, 12,055 made
Class: Sports car
Predecessor: SS Jaguar 100
Successor: Jaguar XK140
Assembly: United Kingdom: Holbrook Lane, Coventry (1948–1951), United Kingdom: Browns Lane, Coventry (1951–1954)
Related: Jaguar C-Type
Layout: FR layout
Body style: open two-seater, 2-seat fixed head coupé, 2-seat drophead coupé
Engine: 3.4 L XK I6
Transmission: 4-speed manual
Wheelbase: 102 in
Length: 173 in
Width: 61.5 in
Height: 52.5 in

Specification summary from Wikipedia (CC BY-SA 4.0). Measured facts from Wikidata (CC0). Check the linked sources for citations.

More photos

Sources

Wikidata — https://www.wikidata.org/wiki/Q1422337CC0 1.0 · retrieved 2026-10-01
Wikipedia — https://en.wikipedia.org/wiki/Jaguar_XK120CC BY-SA 4.0 · Text © Wikipedia contributors; revision 1368146942 · retrieved 2026-10-01
Wikimedia Commons — https://commons.wikimedia.org/wiki/File:1950_Jaguar_XK120_34.jpgCC BY-SA 3.0 · Photo: Sfoskett · retrieved 2026-10-01
Car Model Index — https://models.autoculturesociety.com/Compiled record. Sources that do not permit reuse are not copied; this index is credited instead.