These were mostly roadsters built up on specially made aluminum monocoques and clad with aluminum body panels. Even the hardtop, fiberglass on the standard car, was of aluminum.
The front space-frame remained steel, as on later Jaguar D-Types, and for the same reason: For this application, steel was effectively as light as magnesium and much easier to fabricate. But just about everything else was redone to save weight.
The engines even revived the aluminum-block idea of the late 1950s, for a reduction of 84 pounds. Total weight-saving over the standard roadster was on the order of 500 pounds -- some 20 percent. About 80 pounds of that was later put back on by installing a very stoutly constructed five-speed ZF gearbox from Germany.
While the Lightweights' suspension looked standard, it was, in fact, heavily modified, with different chassis pickup points for altered geometry, and certain parts adopted from contemporary Jaguar sedans because they were stronger.
Torsion bars, springs, shocks, and sway bars were all stiffer, of course, as were the rear subframe mounting rubbers (the car's own designers evidently feeling some small amount of compliance was necessary).
Front brakes were beefier, again thanks in part to some sedan pieces, while the rear binders were basically stock but newly fed with cooling air through special ducts. Instead of the normal wire wheels, the Lightweights had lightweight pierced discs that looked like the old D-Type's but were 15 inches in diameter instead of 16.
Though all-aluminum, the engine also strongly resembled the old D-Type's, having the wide-angle 35/40 cylinder head, fuel injection, and dry-sump oiling. Compression ratios ranged up to 10.0:1 and, during the engine's development life, horsepower reached as high as 344 at 6,500 rpm.
That ultimate engine was installed in the ultimate XKE bodyshell, one of a series of super-streamlined fastback coupes wind-tunnel designed by Malcolm Sayer, Jaguar's astute, always active aerodynamicist.
As entered at LeMans 1964, this version was reported to whistle up as much as 6300 rpm in top gear down the Mulsanne Straight, which gearing charts showed to be 176 mph. By this time, though, LeMans was being dominated by a different class of purpose-built racers capable of another 25 mph or more. Anyway, neither of the Lightweights that started that year's 24-Hours lasted to the finish.
To Jaguar enthusiasts who are also racing fans, the Lightweights were the high-water mark of the factory's competition activities in the 1960s. But as modified road cars, they simply had built-in limitations and were soon outclassed in top-line international racing. Ferrari kept making faster coupes, and also stayed abreast of advancing technology in racing as a whole. Jaguar did not, or rather, did not seem to.
We know now that, in deepest secrecy, chief engineer William Heynes and his staff built and tested a state-of-the-art mid-engine racing sports car with a new 5.0-liter, quadruple-camshaft V-12 of enormous power (reportedly over 500 horsepower).
Completed around 1966, this XJ13 could have carried the British colors at LeMans against the Italian Ferrari "Prototypes" and the Anglo-American Ford GT40. But Jaguar management decided against the venture, considering it more important to concentrate limited resources on improving production cars.
For more on Jaguar and other great cars, see:
- Jaguar Cars: Check out more information on the great sporting cats.
- How Sports Cars Work: Get the lowdown on hundreds of fantastic sports cars from the 1940s to today.
- Classic Cars: Learn about the world's most coveted automobiles in these illustrated profiles.
- Ferrari: Learn about every significant Ferrari road car and racing car.
- New Jaguars: Reviews, ratings, prices, and specifications on the current Jaguar lineup from the auto editors of Consumer Guide.
- Used Jaguars: Reviews, recalls, trouble spots, and more on pre-owned Jaguars starting with the 1990 model year. From the auto editors of Consumer Guide