The Jaguar XJ13 is one of the most visually appealing cars of all time. It carried a nameplate of one of the most successful marque's at LeMans during the 1950's, Jaguar, with five wins in just seven years. The engine that conjured up the wins for the British marque was a direct descendent of the famed XK six-cylinder that could be found in their successful and stunning line of road going vehicles. Jaguar's reign at LeMans was brought to an end when their D-Type was made obsolete due to new racing regulations which limited engine displacement to just three liters. Jaguar returned to LeMans a few years later with a racing version of their E-Type but it was no match for the potent Ferrari's.
Jaguar's racing program was officially over, but designs continued on a new engine and chassis that cold carry the Jaguar name across the LeMans finish line faster than its competition. As racing regulations became relaxed during the early 1960s, Jaguar saw their chance to return with a V12 engine. The car was drastically different to the prior racing C and D Type cars. It had a mid-engine rear drive layout and a design meant to take advantage of the fast-passed course and sweeping curves of LeMans.
Claude Bailey was given the task of developing a new engine. There were seven prototype engines created with two built to racing specifications and fitted with twin overhead camshafts. The engine was created from aluminum with the six cylinder banks mounted at a 60-degree angle. Experiments were done with carburetion, such as the six twin choke setup, but later replaced in favor of the more advanced Lucas fuel injection system. The carbureted versions produced 445 horsepower in comparison to 500 horsepower with fuel injection. The engine had a displacement size of nearly five liters and could be further tuned to gain a couple hundred more horsepower.
The design duties were given to Malcolm Sayer who had been responsible for designing the C and D-Type race cars of the fifties and sixties. This was another big task, as accomplishments on the racing circuit usually translate into sales for the production based cars. Poor performance usually does the opposite. The crew began with a new monocoque chassis with the layout and engine bay similar to the Lotus 25. Just as with the engine, the chassis was formed from aluminum which eliminated the need for steel subframes to carry the suspension. The engine was used as a fully stressed member and the engine and transmission carried the rear suspension. The Sayer designed body was created from aluminum and was finished near the close of 1966. With all the use of aluminum and other weight-saving techniques, the car weighed in at just under 1000 kg.
This was the Experimental Jaguar Number 13, which served as the basis for the vehicles name, the XJ13. It was brought the track for its inaugural outing in early 1967. This clandestine outing was to test the vehicles capabilities and discover its shortcomings. David Hobbs drove the car on the MIRA track and easily broke the track record. It was now ready for LeMans.
The entire project had been done in secret, as the Board of Directors felt it may have a negative effect on the sale of their six cylinder sports cars. As the XJ13 was being finalized and prepared for serious competition, rule changes were made and immediately the car was obsolete. 1968 regulations for prototype racing cars were set at a maximum of three liters. The Jaguar XJ13 was retired before it ever circled the track in formal competition. Work continued on perfecting the V12 engine for use in production vehicles. By 1971 the engine would enter into production in the third generation of the E-Type. The XJ13 was used in a publicity video. During the taping, a tire blew on the MIRA track and the vehicle was nearly destroyed. This was its first public outing. Jaguar later had the car rebuilt and upon completion was shown at events as both a static display and in driving form. One of the engines, the better of the two, was destroyed due to over-revving. The other engine was fitted but the car could now only be driven at slow speeds. This engine used a welded piston which hindered the car from its true potential. The vehicles sad history does not end there; in recent years it fell off a curb and its sump was punctured. After this, the straw that broke the camels back as it were, the car was retired to the museum. Since then, the 'good' engine has been rebuilt, the body repainted, and the chassis repaired as needed.
The car now resides in the Jaguar Daimler Heritage Museum in the U.K. It is brought out only for special appearances. by Daniel Vaughan | Dec 2007The Jaguar XJ13 was designed to compete in the Le Mans 24-hour race in the mid-1960s. The first, and what would turn out to be the only, example of the ill-fated car was completed in 1966. Before the XJ13 had even left the secret back room in Coventry where it was assembled, its potential was eclipsed by a new all-conquering Ford. Teamed up with Carroll Shelby, Ken Miles and other serious contenders with a few races under their respective belts, the American car giant produced the lighter, more powerful 427ci Ford GT40 in the same year and for the next four Le Mans races it proved unbeatable. In light of this, Jaguar didn't even bother to compete and XJ13 was left to gather dust.
Jaguar had considered the manufacture of a V12 engine as far back as 1955, initially for racing purposes, and then developing a road-going version, unlike the original XK which was designed as a production engine and later pressed into racing service. The engine design was essentially two XK 6-cylinder engines on a common crankshaft with an aluminum cylinder block, although there were naturally differences in the inlet porting, valve angles and combustion chamber shape. The first V12 engine ran in 1964; this still-impressive 502bhp 5 liter mill would probably have won the 1964 Le Mans if the car it was intended for had been ready at the same time as its powerplant.
The idea of a mid-engined prototype was first considered in 1960; however, it was not until 1965 that construction began on XJ13 with the first and only example running by March of 1966. The aluminum body was designed by Malcolm Sayer, the aerodynamicist responsible for the Jaguar C-type, D-type, E-type and the later XJ-S, who used his Bristol Aircraft Company background to build it using techniques borrowed from the aircraft industry. XJ13's intended engine found itself mounted behind the driver, used as a stressed chassis member together with the five-speed manual ZF Transaxle that drove the rear wheels. Up front, the suspension wishbones were similar to that of the E-Type, but where the E-Type used longitudinal torsion bars, XJ13 had more conventional coil-over spring and damper units. At the rear there again remained similarities with the E-Type's subframe concept and components, largely the use of driveshafts as upper transverse links, yet the rest was quite different, with two long radius arms per side angling back from the central body tub together with lower links.
The development of XJ13, although treated seriously by the designers, was never a priority for company management (despite Jaguar's Assistant Managing Director Lofty England's Le Mans success in the 1950s), and became less so following the 1966 merger with British Motor Corporation and later British Leyland. By that time, Ford and Shelby's continuous development of the 7 liter GT40 rendered XJ13 obsolete by the time the prototype was complete. Testing at MIRA and even Silverstone confirmed that the car still required considerable development to make it competitive and thus was put into storage and with no further examples ever planned or made.
XJ13 found itself in a sticky situation a few years later. In 1971, the Series 3 E-type was about to be launched with Jaguar's first production V12 engine, a 5.3 liter unit derived from the development of XJ13. Naturally, British Leyland's publicity team wanted a shot of XJ13 at speed for the opening sequence of the film launching the V12 E-Type. On the 21st of January, XJ13 was taken to MIRA for the filming with Jaguar test driver Norman Dewis at the wheel. Unfortunately, the prototype magnesium wheels had suffered from internal corrosion and one disintegrated at speed, the result being that car rolled heavily and was nearly destroyed although Dewis was fortunately unharmed. The wreck of the car was put back into storage. Some years later, the car was rebuilt, to a specification similar to the original, using the body jigs made for its original construction. The car is now displayed in the Jaguar Daimler Heritage Trust collection.
About ten years ago, the Trust turned down a $7,000,000 offer for the unique prototype of Jaguar's first V12-powered car. While its racing pedigree was never allowed to take off, the significance of this very special car ranks high in the annals of British supercars let alone the history of post-war prototypes on the grand circuit. Having had the unique opportunity to inspect the sole example of XJ13 myself while touring the British Motor Heritage Trust, this author completely understands and applauds the efforts of the dedicated enthusiast that built and cares for the example on offer here. As a replica of XJ13, the 'Green Machine' is a representative of the original car, yet certain liberties have been taken in the basic structure, powertrain and ancillary equipment to make the vehicle not only more civilized for street use but also more potent and enjoyable for the end user. Where the original vehicle was an all aluminum monocoque structure, the Green Machine utilizes a modern space frame with FRP and aluminum body panels affixed to it. Naturally, the original car was also a strictly racing machine with no thought given to the usual creature comforts of street legal vehicles nor was any effort considered to comply with the legal requirements of public road usage. These items have been addressed in this car, from its conversion to left-hand drive to the removable top clearly not fitted to the original.
As mentioned earlier, XJ13 was powered be an experimental 5 liter V12 engine that predated the production 5.3 found in late E-Types and as such would be an engine that would be extremely costly to reproduce. As a result, a more practical powerplant was built based on the relatively-common and available Jaguar V12 engine. Bored and stroked to 7 liters from the original production displacement, incidentally, within a couple cubic inches from the displacement of the GT40 that put the XJ13 out of contention before it even emerged - the engine was heavily tuned with extensive port work performed to the cylinder heads and a custom set of camshafts from solid blanks were fabricated. New enlarged throttle bodies were then produced and fitted to the similarly port-matched Jaguar intake manifolds and cool ambient air is fed via rear fender scoops to a large low restriction air filter system. On the exhaust side the engine is fitted with free flowing stainless steel headers and low-restriction silencers. Advanced engine management is by a TECH 2 fully programmable electronic system with the added control parameters utilizing two systems which control each bank as separate 6 cylinder engines. Where the original engine developed 502 horsepower and 386 lb/ft of torque, the 'Green Machine's' mill puts out 500bhp and an amazing 518 foot-pounds of grunt. Relative to its kerb weight of just 2460 pounds it is anticipated that performance of the Green Machine will be quite spirited indeed. Like the original, the transaxle is a ZF 5 speed with a Centerforce single plate dual friction clutch bolted to a lightweight flywheel. Adding additional braking surfaces, the Green Machine utilizes 17-inch wheels wrapped in Pirelli P-Zero tires (up from XJ13's 15-inch magnesium rims) which permits ventilated and cross-drilled disc brake rotor diameters of 13- with 4-piston staggered bore calipers.
As the most unique replica of Jaguar's most advanced racing prototype in its day, this tribute to the XJ13 would make a captivating addition to any enthusiast's stable of fine automobiles.Source - Russo & Steele
This 1966 Jaguar XJ 13 is a recreation created by Predator Performance in Tampa, Florida. It is a left-hand drive example created from as much road car production Jaguar parts as possible. Its dimensions are true to the original shape and size with....[continue reading]
Built as a potential Le Mans contender, it never competed in any race. Its development inevitably had to take second place to that of the much more important new salon car which became the XJ6, launched in 1968. By the time XJ13 was completed, its de....[continue reading]