Jaguar XK-120 History (1948-1954)
Originally designed to showcase Jaguar's new twin-cam motor, the XK-120 was an immediate hit when it debuted in October of 1948.
Strong public reaction convinced company founder William Lyons to put the streamlined roadster into production, with the Jaguar XK-120 becoming a huge influence in the next few decades of sports car history.
The XK motor, described by many as jewel-like, was built under direction of William Heynes.
The under-square 3.4 litre size was derived by an 83 mm bore by 106 mm stroke.
Underneath the polished covers were a pair of chain-driven camshafts, which sat atop an aluminum-alloy head.
Hemispherical combustion chambers allowed use of larger valves, with domed cast-aluminum pistons boosting the compression ratio up to 8.0:1. With a pair of sidedraft carburetors, output was 160-horsepower and an equally impressive 195 lb/ft of torque.
Able to reach 120 miles-per-hour, the XK-120 was the fastest production car of its day.
With intentions of making just a few hundred cars, the first run of XK-120's were aluminum-bodied, but overwhelming demand quickly prompted the switch to pressed steel. Borrowed from Jaguar's big sedans, the modified frame was actually sturdier than needed, making the XK heavier than other sports cars of the day. Riding on 16" x 6" tires, the chassis featured torsion-bar independent front suspension with ball joints, and semi-elliptic leaf springs in the rear. The car was narrow, tracking 51 inches at the front and 50 inches in the rear. Though not as responsive as rack and pinion (as would come on the XK-140), most drivers felt the recirculating-ball steering system felt light and smooth. All-wheel drum brakes were marginal at best.
A closed version of the XK-120 joined the roadster in 1951. Deluxe accoutrements in the fixed-head coupe included wood-veneer dashboard and door tops, with both models getting leather seats. The nearly vertical steering column was telescopically adjustable to suit shorter or taller drivers.
A second roadster model, the drophead coupe, was offered in 1953, and featured a padded, folding top with roll-up side windows.
Jaguar XK-120 In Competition
A race-prepared XK-120 finished first in class at the 1951 French Le Mans race, Jaguar's first win there since 1935. One of the more impressive of its many records was the grueling "Seven Days and Seven Nights" competition of 1952. A fixed-head XK-120, near the end of the event, broke a spring, and was still able to finish and set a new record with an average speed of 100.31 mph.
In June of 1954, NASCAR staged their first road-course race. The event, held at Linden Airport, New Jersey, was open to both American stock cars and foreign sports cars.
Driver Al Keller drove his #4 XK-120 to victory, becoming the first and only driver in the history of NASCAR's premier series to win a race in a foreign-made car.
In the early Fifties, when Chevrolet engineers started work on their upcoming Corvette sports car, an XK-120 roadster was rolled into the design studio and studied. The long nose-short tail was copied, as well as its 102-inch wheelbase. After Ford Motor Company heard about their rival's eminent new sports car, they too used the Jag's dimensions for their forth-coming two-seat Thunderbird .
Orders for the XK-120 came from every continent, with nearly 60% of them being exported to America. This went a long way to help England, still recovering from five terrible years of war. The XK motor was a marvel of engineering, and would power Jaguars for another two decades, including the 1961-1969 Jaguar XKE (E-Type). Over 12,000 XK-120's were built in the seven years produced.
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