• Manufacturer Jaguar Cars
  • Production 1948–1954
    12,055 made
  • Body style(s) 2-seat roadster (OTS)
    2-seat coupé
    2-seat Drop Head Coupé
  • Class Sports car
  • Successor Jaguar XK140
  • Engine(s) 3.4L XK I6
  • Height 52.5 in (1334 mm)
  • Length 173 in (4394 mm)
  • Width 61.5 in (1562 mm)
  • Wheelbase 102 in (2591 mm)
  • Layout FR layout
  • Predecessor "Jaguar" SS 100
  • Related Jaguar C-Type

The history of the Jaguar XK120


The Jaguar XK120 is a sports car which was manufactured by Jaguar between 1948 and 1954. Jaguar's first post-war sports car, it succeeded the SS 100, which ceased production in 1940.
The XK120 was launched in roadster form at the 1948 London Motor Show as a testbed and show car for the new Jaguar XK engine. It caused a sensation, which persuaded William Lyons to put it into production.
The "120" in its name referred to its 120 mph (193 km/h) top speed (faster with the windscreen removed), which made the XK120 the world's fastest standard production car at the time of its launch.
It was available in two convertible versions first as the roadster (designated OTS, for open two-seater, in America), then also as a drophead coupé, or DHC, from 1953 and as a closed, or "fixed-head" coupé (FHC) from 1951. The DHC was a more deluxe model, featuring a beautiful wood dashboard and wood features on the door interiors.
The roadster version was successful in racing.
The first 242 cars, all roadsters hand-built between late 1948 and early 1950, had aluminium bodies on ash frames. To meet demand it was necessary for the mass-production versions, beginning with the 1950 model year, to have pressed-steel bodies. They retained aluminium doors, bonnet, and boot lid.
With alloy cylinder head and twin side draft SU carburetors, the dual overhead-cam 3.4 L straight-6 XK engine was comparatively advanced for a mass-produced unit of the time. With standard 8:1 compression ratio it developed 160 bhp (119 kW).  A 7:1 low compression version was also available to cope with low quality fuel. This same basic design of the XK engine, later modified into 3.8L and 4.2L versions, survived into the late 1980s.
All XK120s had independent torsion bar front suspension, semi-elliptic leaf springs at the rear, recirculating-ball steering, telescopically adjustable steering column, and all-round drum brakes that were prone to fade. Some cars were fitted with Alfin brake drums to help overcome this brake fade.
The roadster's lightweight canvas top and detachable sidescreens stowed out of sight behind the seats, and its barchetta-style doors had no external handles; instead there was an interior pull-cord which was accessible through a flap in the sidescreens when the weather equipment was in place. The windscreen could be removed for aeroscreens to be fitted.
The drophead coupé had a padded canvas top, which folded onto the rear deck behind the seats when not in use, and roll-up windows. The windscreen was fixed. Dashboards and door caps in both the FHC and DHC were wood-veneered, whereas the roadster's were leather-trimmed. All models had removable spats covering the rear wheel arches, which enhanced the streamlined look. On cars fitted with optional centre-lock wire wheels (available from 1951), the spats were omitted as they gave insufficient clearance for the two-eared Rudge-Whitworth knockoff hubs.
In addition to wire wheels, upgrades on the Special Equipment, or SE, version (called the M version in the United States) included increased power, stiffer suspension and dual exhaust system.
XK 120 Engines: Model / Years / Displacement / Configuration / Bore-Stroke / Carburettor / Power
XK 120 3.4 / 1948-1954 / 3442 cc / DOHC Straight-6 / 83 mm-106 mm / Double SU H6 / 160 bhp (119 kW; 162 PS) @ 5000 rpm
XK 120 3.4 SE  / 1951-1954 / 3442 cc / DOHC Straight-6 / 83 mm-106 mm / Double SU H6 / 180 bhp (134 kW; 182 PS) @ 5300 rpm
XK 120 3.4 SE (C-Type Head) / 1951-1954 / 3442 cc / DOHC Straight-6 / 83 mm-106 mm / Double SU H8 / 210 bhp (157 kW; 213 PS) @ 5750 rpm
The Motor magazine road-tested an XK120 roadster in 1949. With hood and sidescreens in place, it achieved a top speed of 124.6 mph (200.5 km/h), accelerated from 0-60 mph (97 km/h) in 10.0 seconds and consumed fuel at the rate of 19.8 miles per imperial gallon (14.3 L/100 km; 16.5 mpg-US). The car as tested cost £1263 including taxes.
In May 1949, Jaguar demonstrated an XK120 roadster to the press on the high-speed autoroute between Jabbeke and Aeltre 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 for him. 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 136.596 mph (219.830 km/h), making the XK120 the world's fastest production car.
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 however management dissatisfaction with the engine resulted in the project being cancelled prior to production.

Type 1940s 1950s 1960s 1970s
5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
Sports   XK120 XK140 XK150 E-type S1 E S2 E-type S3 XJ-S
Saloon     Mark 1 Mark 2, 240, 340    
      S-Type     XJ-C  
      420 XJ6 S1 XJ6 S2
Mk IV Mk V Mk VII Mk VIII Mk IX Mk X 420G   XJ12 S1 XJ12 S2
Supercar     XKSS    
Racing     C-Type D-Type     E-Type   XJ13     XJ-C XJ41 / XJ42
Corporate ownership Independent BMH British Leyland

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