1949-1961 Jaguar XK Sports Cars

The genesis of the Jaguar XK-120 can be seen in a 1938 experimental, a surprise exhibit that electrified visitors at that year's London Show. Designated "Jaguar 100," it was a strikingly streamlined closed coupe combining a rounded, two-place cockpit, sloped tail, and fulsome fender shapes with the SS roadster's long hood and fine-mesh vertical grille.

Many sports car buffs would have been happy with a postwar edition of this job, but there were many others who would have simply preferred a more powerful SS 100. As far as they were concerned, there wasn't a thing wrong with the "British traditional" sports car -- spartan interior, stiff ride, classic styling, minimal weather protection, and all -- especially for competition, where prewar MGs, Morgans, Singers, and HRGs again began dominating British hillclimbs and track events in the late Forties.

Significantly, SS 100s were also running again, and winning. When the ultramodern XK-120 arrived, many enthusiasts doubted whether the new streamlined beauty would be able to carry on its forebear's enviable racing record. Meanwhile, a number of the earlier cars had been purchased by cash-laden GIs, and the SS 100 quickly became part of the growing sports car phenomenon in America. No less a celebrity than the late Dave Garroway (the first host of TV's morning "Today" show) took to the SCCA circuits with a mildly customized roadster featuring alligator hides on seats and dash.

While sports car buffs debated the merits of classic traditionalism versus progressive modernity, buyers were quick to endorse the new XK-120. Initial sales were as strong as Lyons had anticipated, and a July 1948 production startup, well in advance of the new model's debut, ensured ample inventory and prompt customer delivery. Those customers found themselves in good company, for journalists on both sides of the Big Pond were quick to sing the praises of this sensational Jaguar. If not the ultimate in engineering sophistication, the XK-120 was unquestionably a state-of-the-art sports car -- and one that mere mortals could actually afford.

Built on an extraordinary strong box-section chassis, the XK-120 featured fully independent front suspension of modern geometry -- upper and lower wishbones and longitudinal torsion bars -- in contrast to the old prewar leaf-sprung solid axle. At the rear was a live axle carried on unusually long semi-elliptic leaf springs made of silico-manganese steel. Girling telescopic shocks were used in front; piston units served at the rear. Brakes were British-made Lockheed drums with twin leading shoes and ample 12 x 2.25-inch dimensions. Adding to driver comfort and handling ease was a vastly improved recirculating-ball steering system. The large 17-inch-diameter steering wheel was mounted on a steeply raked Burman-Douglas steering column with four inches of telescopic adjustment via a screw-type collar. The driver and one lucky passenger sat in shapely bucket seats upholstered in top-grain cowhide and offering up to six inches of fore/aft travel.

On the next page, learn about the engines that powered Jaguar's XK-120 sports cars.

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The heart of the Jaguar XK-120 -- and the main attraction for the technically minded -- was its engine: a lovely new inline six with dual overhead camshafts. The overall design concept for this advanced powerplant had been conceived during the war by Lyons -- later knighted by Queen Elizabeth II in partial recognition of this achievement -- along with chief engineer William Heynes. Both men recognized that fuel costs and car taxes would escalate once peace returned, so obtaining maximum power per unit of displacement became the main focus of their development effort.

To this end, engine designer Harry Weslake was called in near war's end to assist in the final engineering. The concern with efficiency and the precedent of several low-volume, high-performance European cars explains the decision to adopt the twincam configuration, even though dohc engines were hardly the norm in prewar British cars. It also explains Weslake's choice of large main bearings and hemispherical combustion chambers for the new six, which arrived with a displacement of 3,442cc (210 cubic inches).

While sports car buffs debated the merits of classic traditionalism versus progressive modernity, buyers were quick to endorse the new XK-120. Journalists on both sides of the Big Pond did too. If not the ultimate in engineering sophistication, this sensational Jaguar was unquestionably a state-of-the-art sports car -- and it was affordable.

Designated the XK-series in production form, the twincam six was one of 10 powerplants being considered for the new sports car by late 1947, all developed under the "XJ" project code. Actually, the most promising of the lot was a 1,996cc (121.8-cubic-inch) four of 80.5 x 98.0mm (3.17 x 3.86-in.) bore and stroke, and Weslake selected it as the basis for the eventual XK-120 engine. Though output was ample, some 145 horsepower at 6,000 rpm, the four would never be used in a production Jaguar. However, it did make history in an experimental MG.

At the request of Lt. Col. "Goldie" Gardner, the four was turned over to the Abingdon people, who slotted it into the EX-135 streamliner being prepared for an assault on the Bonneville Salt Flats. In a sterling test of Jaguar's dohc concept and Weslake's engineering savvy, this amazingly tough little engine propelled the then 63-year-old Gardner to numerous speed marks in August 1952, including an impressive 148.7-mph average for the 100 kilometers. This feat immediately touched off rumors that Jaguar was about to field a 2.0-liter challenger to Triumph's then-new TR-2 and similarly sized sports cars from Britain and the Continent, but Lyons and company had no such intent. Even so, speculation that a "little cat" was in the offing persisted through 1953-1954.

As noted, the experimental four was Weslake's choice as the basis for the production XK-series six. The transition was straightforward enough. First, two more cylinders were added and bore was brought up to 83.0mm (3.27 in.), yielding displacement to 3.2 liters (195.2 cubic inches). However, low-rpm torque was judged insufficient, so stroke was stretched to 106mm (4.17 in.), resulting in the final 3,442cc. With dual SU H.6 carburetors, the twincam six initially delivered an honest 160 horsepower at 5,200 rpm as installed, which was sufficient to see XK-120 prototypes to a maximum 120 mph, hence the model designation.

On the next page, learn how the XK-120's engine performed on the road.

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A milestone car by almost any definition, the Jaguar XK-120 was greeted with high enthusiasm everywhere it appeared. Originally, only the open roadster was to be offered, but because buyers in several prime export markets, particularly the U.S., had shown a preference for more civilized accommodations, a drophead coupe (i.e. convertible) with proper glass side windows was announced shortly after introduction. A fixed-head (closed) coupe appeared at the Geneva Show in March 1951 to complete the line.

The first 242 roadsters, all early-1949 models built in late 1948, had light-alloy bodywork, after which pressed steel was used exclusively. Because of their obvious rarity, the "alloy" XKs command the highest prices on today's collector market, and are found with both right- and left-hand drive (serial numbers 660001-660058 and 67001-670184, respectively). This writer was privileged to examine a pair of alloy-body cars being restored, and found the coachbuilder's art evident in such details as the hardwood door frames, the latch surface bolsters, and the curved bows supporting the tonneau just ahead of the trunklid.

All XK-120s wore narrow, somewhat fragile bumpers that complemented the curvaceous body lines but didn't stand up well to America's rude and perilous parking habits.

Americans lulled into premature senility by the cushy, chrome-laden Detroit iron of the early postwar period quickly discovered that this sleek cat was everything many domestic dealers flatly declared a sports car could not be.

Before embarking on a solo run, it was helpful to read the owner's manual, grandly titled the "Operating, Maintenance and Service Handbook," to familiarize yourself with the controls. Seated behind the large steering wheel, you viewed a full set of no-nonsense, white-on-black Smith's instruments, which even then were obligatory for a British sports car. The Jaguar's complement included a "revolution counter" with inset manifold pressure gauge (early models) or clock at the bottom of the dial; an ammeter, oil pressure gauge, and water temperature gauge combined in a separate dial; a "petrol gauge" that doubled as a crankcase oil level indicator by pressing a button before starting the engine (capacities were 17.5 gallons and 12.5 quarts U.S., respectively), and a large speedometer with trip and total mileage recorders.

All were housed along with the ignition switch and separate press starter button in a leather-covered panel, mounted centrally and angled downward from the upper dash rail. The coupe's instrument board had a slightly different arrangement and was finished in burled walnut. A manual choke was customary in those days, but it was seldom needed in the XK-120 because, as the factory claimed, the "auxiliary starting carburetter is entirely automatic and controls the mixture strength without assistance from the driver." Other cockpit delights were a short gear lever with remote linkage, a gearbox dipstick (located well forward on the tunnel top), racing-style "fly-off" handbrake, and a small grab bar ahead of the passenger seat.

Appropriately for a sports car, the XK-120 was blessed with high-geared steering giving just 23/4 turns lock-to-lock and a compact 31-foot turning diameter, though steering effort was predictably heavy. Braking from speed brought out surprisingly little nosedive, a benefit of the slight rear-end weight bias that also enabled rapid getaways without undue wheelspin. And make no mistake: the XK-120 was quick even by today's standards. With the optional 3.54:1 final drive (the middle ratio of three available), a well-broken-in example could reach corrected maxima of 30, 61, and 88 mph in the lower three gears, and sail on to that magic 120 mph in fourth.

A roadster tested new by the author sprinted from 0 to 60 mph in 9.7 seconds, flew through the standing-start quarter-mile in 18.0 seconds at 86 mph, and could run at precisely 100 mph on the flat at a relatively relaxed 4,390 rpm. At $3,600 POE in 1952, the XK-120 was indeed quite pricey, but nowhere else could you get this unrivaled combination of "grace and pace" for less. For those with the wherewithal to indulge their motoring fantasies, this cat was one whale of a buy.

Go to the next page to learn about a variation on the XK-120, the Jaguar XK-120MC.

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Jaguar obliged drivers who wanted even more speed with the XK-120MC. Priced at $800 above the standard offering, this "special equipment" model boasted a high-lift camshaft and dual exhausts that raised rated output to 190 horsepower at 5,500 rpm. Though about 50 pounds heavier than the normal XK-120, the MC could breeze through the 0-60 mph dash in 8.6 seconds, and its quarter-mile acceleration came down to 16.8 seconds. The MC was supplied without the distinctive rear wheel spats usually found on 120s, but this allowed you to show off the standard wire wheels with Rudge-Whitworth knock-off hubs. Stiffer front torsion bars completed the package.

If the brilliant twincam six delivered the goods on the road, how would it fare in the heat of international competition? Given its long-time interest in racing, it was only natural that Jaguar would want to find out, and in early 1950 it decided to field a special car built around XK-120 components for the famed 24 Hours of Le Mans. The result was the legendary C-type, one of the most memorable competition sports cars in history. Built around a lightweight tubular steel chassis on a shortened 96-inch wheel-base, it was powered by what was a mildly modified version of the production engine. Changes comprised special cylinder head with straight inlet ports, high-contour camshaft profile, big horizontal carburetors, special free-flow exhaust system, and lightened flywheel. Rated power jumped to 210 horsepower at 5,800 rpm, and maximum torque soared to 220 lbs/ft at 4,000 rpm.

Running on a beefed-up stock suspension, the C-type was clothed in smooth aluminum-alloy bodywork that held its race-ready weight to around 2,175 pounds. Naturally the car was competitive, and it had the necessary staying power. Jaguar won Le Mans 1951 outright, and went on to score firsts at Silverstone, Spa, and other circuits in 1952. The following year, C-types came home first and fourth in the Rheims 12-hour contest; placed first, second, and fourth at Le Mans; and finished 1-2 at the Nürburgring (where XK-120s took fourth and fifth overall). In 1954, the C-types and a gaggle of production Jaguars again won at Spa, at Zandvoort in the Dutch Grand Prix, and at Le Mans, where the new D-type was overall runner-up.

In all, 11 factory-sponsored C-types were completed, along with another 43 units built for sale on the "open market" at a nominal price of $6,000 each. Today, you can multiply that figure by a factor of at least seven for even a barely restorable example of this rare and ferocious feline.

Go to the next page to read about the follow-up models to the XK-120, the Jaguar XK-140 and XK-150.

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Introduced in late 1954, the new Jaguar XK-140 incorporated several of the engine mods developed for the racing program, which made the standard version quite similar in output and performance to the now-superseded XK-120MC. Competition experience has a way of showing up later on a manufacturer's roadgoing models, and so it was with the C-type engine and the next generation of Jaguar sports cars.

The same three body styles returned, and appearance was unchanged apart from heftier bumpers (a concession to the American market) and a longitudinal chrome hood strip running from the nose to the center of the split windshield. Other alterations included a switch to more precise rack-and-pinion steering, better brakes, higher rates for both the front torsion bars and the rear leaf springs, and adoption of the previous MC's special equipment as standard. Laycock de Normanville overdrive, controlled by a faciamounted toggle switch, appeared as a new option, and Borg-Warner automatic transmission was offered at extra cost late in the model run, which ended in early 1957.

There was also an MC version, announced in 1955, packing the same horsepower as the racing C-type. This car could spring from 0-60 mph in about 8 seconds and was some 5 mph faster flat out than its 120 predecessor. However, under pressure from American law enforcement authorities, Jaguar was forced to muzzle the lovely exhaust note on its tuned engine from a roar to a relative purr.

A changing market hastened the XK-140's replacement, which debuted in mid-1957 as the XK-150. This final variation on Sir William's stunning original design theme was Jaguar's direct reply to cars like the BMW 507 and the Mercedes-Benz 300SL, which offered similar performance and roadability while better catering to the growing American demand for more refinement and comfort.

Accordingly, the 150 was plusher and more civilized than any previous XK. The basic bodyshell was substantially restyled with higher front fenders, a wider grille, and a curved one-piece windshield. Critics bemoaned the heavier. more "matronly" appearance, especially since it was matched by a gain in curb weight, but fortunately the extra heft didn't spoil the good overall handling balance. Aside from a slightly larger 33-foot turning diameter, the familiar XK chassis was retained intact. However, Jaguar scored a production first by replacing the old fade-prone drum brakes with servo-assisted Dunlop disc brakes at each wheel, which easily compensated for the weight gain. It was another example of how racing can improve the breed, as discs had been used successfully on the competition D-type.

Continue to the next page to learn about the features found on the sporty and speedy Jaguar XK-150.

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Initially, the Jaguar XK-150 was offered only as a coupe and convertible, almost as if Jaguar were testing reaction to this obviously fatter cat. When it arrived some nine months later, the roadster was bereft of its cut-away doors, and purists complained. The roadster proved the least popular of the three XK-150 models, accounting for less than a fifth of the total number built.

Besides disc brakes, the XK-150 was notable in being the first postwar Jaguar sports car available with a choice of engine sizes. It was announced with the 210-horsepower version of the 3.4-liter twincam six as used in the XK-140MC. Beginning in the fall of 1959, a bored-out 3,781cc (231-cubic-inch) unit with 20 extra horses was offered as an option, usually teamed with Borg-Warner automatic for the U.S. market.

Following past practice, Jaguar also listed "Special Equipment" 150s powered by "S" versions of each engine, with three huge SU HD.8 carburetors, straight-port head, 9.0:1 compression, and wilder cam timing. The tuned 3.4-liter spun out 250 horsepower at 5,500 rpm, while the 3.8S delivered fully 265 horsepower at 6,000 rpm.

Neither S model was available with automatic, and only discreet badges identified them externally. But just put your foot to the floor and you knew instantly that you were in charge of a special breed of cat. The 3.8S could see the far side of 135 mph with ease, and 0-60 mph was a matter of 7.0 seconds or so with two aboard. Fuel economy, all things considered, was excellent: 18-20 mpg on American highways at the then-legal 70-mph limit. In fact, any of the XK litter would return this kind of mileage given a driver skilled with a manual gearbox.

Even landmark automotive designs must eventually bow to the march of progress (though the Porsche 911 may be an exception), and by 1961 the XK sports car was clearly in need of replacement. Jaguar was ready with the E-type, a machine as stunningly advanced and exciting in its day as the original XK-120 was in the late Forties.

But the E-type would not have been possible had the XK models not succeeded. And succeed they did beyond all expectations. Jaguar built more than 12,000 of the XK-120s, nearly 8,900 of the XK-140s, and a bit more than 7,900 of the XK-150s. Commercial considerations aside, this line is significant because it ushered in one of the most adaptable and long-lived engines in postwar history. It's still going strong more than 35 years later, and even Jaguar's own lovely V-12 and the advent of American emissions standards haven't been able to kill it. That the sports cars it first powered were possessed of a timeless grace and that elegant charm so peculiarly British only adds to their allure. Long counted among the greats, these Jaguars are still captivating enthusiasts, and seem destined to endure far beyond a lesser cat's nine lives.

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