Jaguar return to racing
Derek Bell and David Hobbs head a new Leyland Cars team of XJ5-3Cs.
It seems almost too good to be true. After years of mostly poppycock rumours a team of official works Jaguars has re-emerged to compete in European motor racing. In an ambitious and obviously costly project aimed at improving the corporate image in the European market-place, Leyland Cars have signed Derek Bell, ex-Jaguar apprentice David Hobbs, British Touring Car Champion Andy Rouse and Formula 5000 driver Steve Thompson to drive two Jaguar XJ 5.3Cs in the European Touring Car Championship. It’s a real “We’re Backing Britain” exercise, with British drivers and a car built exclusively from British parts.
Jaguar Cars Ltd. have had little to do with the exercise. These Leyland Cars-entered, V12 coupes are being developed and built to the latest Group 2 specification almost in their entirety by Ralph Broad’s Broadspeed Engineering Ltd., at Southam, near Leamington Spa. To date only one car has been completed; this has undergone some six hours’ testing at Silverstone and Goodwood, showing potential which had the seasoned Bell quite excited when we spoke to him. Even at this early stage in development he considers this red, white and blue Jaguar to be one of the best balanced cars he has driven. The same car was towed to Geneva for presentation to the CSI during the Geneva Show and homologation will be forthcoming on April 1st, interestingly, the first Jaguar to have been homologated in any form since the E-type.
The racing debut is planned for the Salzburgring 4-hour race, the second round of the European Touring Car Championship, on April 18th, when it seems likely that only one car, for Bell/Hobbs, will be fielded.
Ralph Broad refuses to divulge the power output of the racing V12, but we understand from other sources that the Mk. 1 development version fitted in the test car gives about 530 b.h.p., while 575 b.h.p. is expected from the Mk. 2 engines currently being constructed for racing. The latest Group 2 regulations include a minimum weight for each class, to which any make/model of car in that class may be lightened. In the Jaguar’s case this will he 1,280 kg., plus the weight of the full roll cage. Though the development car turns the scales at 1,400 kg., Broad reckons he’ll have this pared to the minimum before racing starts. It’s interesting to recall that the all-conquering BMW 3.0CSLs built to the old, and more permissive, Group 2 over the last two or three years, weighed 1,125 kg. and reached a maximum power of about 450 b.h.p.
The cylinder block, alloy head castings, the lightened and X-rayed forged-steel crankshaft, connecting rods and flywheel are all suitably improved standard items. Increasing the bore by the regulation 0.6 mm. allowance has given a capacity of 5,416 c.c. (90.6 mm. x 70 mm.) instead of 5,343 c.c. Current Group 2 regulations insist that the Jaguar retains its wet sump lubrication; Broad has overcome this handicap by developing a twin-sump system, one at the front, another at the rear, joined by four tubes. The steering rack passes through the gap between them. A crankshaft “windage tray” directs oil off the crankshaft and diverts it to the back of the sump. Oil pressure blowoff is diverted back to the inlet side of the standard 85 p.s.i. oil pump, avoiding any oil wastage. Broad says that tests so far indicate that his system is effectively preventing surge under this Jaguar’s high cornering forces.
Oil is cooled by a massive Serck cooler mounted behind the Jaguar’s main front grille. The full-width Serck radiator is mounted behind the horizontal lower grille to keep the weight of water well down. An integral water swirl pot, header tank and de-aeration system is mounted under the bonnet.
Broad describes the single overhead camshaft, two-valves-per-cylinder head design as “restrictive” and Group 2 regulations don’t allow the use of the twin-overhead-camshaft heads fitted to the experimental XJ 13 sports/ racing car. For increased efficiency he designed two-part combustion chambers: two-thirds of their capacities are machined into the tops of the Broadspeed-designed and machined, Cosworth-made, forged alloy pistons, the other third in the heads. The larger, alloy-steel valves are deeply inset into the heads to support Broad’s theory that contrary to popular thinking, recessed valves give a better gas flow by feeding the mixture directly down the bore instead of at the side of the bore. A 12:1 compression ratio is used. The heads carry hidural valve guides and inserts and Champion N57R, 14 mm. sparking plugs. Special springs are included, compatible with the racing camshafts, machined out of solid billets of EN 16T and designed with the help of a consultant engineer on dynamics. To withstand the lift, in excess of 0.5 in., larger diameter, inverted tappet buckets are required. The camshaft drives are standard, except for heat treatment of the gears.
Twelve curved trumpets sprout from the Lucas mechanical injection system (Ferrari F1 type) of the prototype engine. The inlet stubs of the Mk. 2 engine will lack individual butterflies, their breathing controlled instead by two butterfly-controlled intakes at the front of an aluminium plenum chamber mounted atop them. The induction will gain a ram effect through these butterflies, mounted behind the front grille. Quadruple SI) low-pressure electric fuel pumps lift fuel from the mandatory 120 litres (26 gallons) Marston safety tank in the boot to a swirl pot mounted under the front off-side wing. A high-pressure Lucas electric pump lifts the fuel from the swirl pot to the metering unit for starting; once the engine has started, a high-pressure mechanical pump takes over, line pressure being some 160 p.s.i.
Maximum revs of this modified V12 are 8,500 r.p.m., with a rev-limiter to ensure that this mark isn’t overstepped. Maximum power occurs at 8,000 r.p.m. and maximum torque (again not divulged) at 5,750 r.p.m.
As the Mk. 1 engine had already completed some 50 hours’ running on the dynamometer and another six hours on the track, Broad was unperturbed when a bearing ran while Bell was demonstrating the car to the Press on the Silverstone Grand Prix Circuit. Before the calamity this Jaguar impressed by its flatness and precision of cornering on the very wet track and by the invigorating bellow from the four exhausts, two each side, leading from beautifully curved exhaust manifolding fabricated by Andy Rouse. Rouse, it should be remembered, is competition workshop manager for Broad as well as Leyland’s leading Dolomite Sprint driver and now Jaguar team member. He has been responsible for much of the racing Jaguar’s construction.
Leyland have managed to homologate the XJ5.3C with a manual gearbox for Group 2. We hope they will be persuaded to make this an optional fitment in production. In racing form the all-synchromesh, Jaguar four-speed gearbox is fitted with close-ratio gears. “Obviously we’d prefer five gears, but the torque of the engine is such that we can manage well enough with four,” says Broad. Both the gearbox and differential, within which lies a Salisbury Power-Lok differential, are fitted with pumps to circulate their lubricants to coolers mounted ahead of the production exhaust-pipe holes in the rear valence. The differential oil is driven by a crescent pump off the pinion flange. To overcome the physical difficulty of operating the 700-800 lb. pressure of the AP clutch’s diaphragm spring without using a servo, Broad has evolved a purely hydraulic operation in which the slave cylinder is concentric with the first motion shaft and acts hydraulically directly upon the pressure plate, obviating the need for a mechanical connection. Pedal pressure is brought down to 60 lb. by this means and Broad regards his system as a breakthrough which might well be of benefit to production cars. There is not a conventional clutch plate lining as such : eight sintered-metallic pads (four each side) are the friction medium.
One thing these racing Jaguars will not lack is a final drive ratio appropriate to the conditions: Broad has a choice of ten, ranging from a 3.07 : 1 ratio offering a theoretical 210 m.p.h. at 8,500 r.p.m. to 5.38 : I, gearing it down to 110 m.p.h. at 8,500 r.p.m.
AP Racing (Lockheed) have developed a totally new racing braking system specifically for this fast, heavy Jaguar. Eight-piston, fourpad calipers are fitted to the 11.97 in. diameter. 11 in. thick, ventilated front discs, and fourpiston, two-pad calipers to the inboard ventilated rear discs, of 11.75 in. diameter by 1.1 in. thickness. The swept area is the same as that of the standard car. Intriguingly, the final racing versions will have provision for cooling the discs by spraying water into the central vents: “But we’ll only use this in dire emergencies, otherwise we’ll run out of water,” comments Broad. A more usual type of cooling is effected at the front via ducts concealed behind the front grille to avoid cutting ducts in the very shallow front spoiler. The inboard rear brakes receive cooling air via NACAR ducts mounted ahead of the rear wheel arches. Hot air is exhausted from the brakes through massive-bore piping, within the boot, to duets in the corners of the rear valence.
The suspension follows conventional Jaguar practice, but with many detail modifications. At the front the forged wishbones are standard, but incorporate spherical bearings and special bushes. There are both inner and outer coil springs, adjustable for ride height by the insertion of spacers. Light alloy Armstrong dampers have been specially designed for the car: they have adjustable abutments and are cooled by air ducts from the grille. The front anti-roll bar is mounted on spherical bearings.
“Third generation” SKF bearings—a new ball-bearing system as used on the Citroen CX—means that there are no front stub axles as such.
At the rear the torque locating arms have been removed and wide-base bottom wishbones made up by taking back at 45 deg. to the chassis a link from the outboard end of the “H” section of the lower suspension arms. BRD have made up heavily-reinforced driveshafts, for the shafts form the top suspension links as well as transmitting the vast power; a broken driveshaft instantly means collapsed suspension. Again there are light alloy Armstrong shock-absorbers and a spherical-bearing-mounted anti-roll bar. Yet another novelty when the cars reach full race-trim will be the facility for driver adjustment of this rear roll bar; as the fuel load decreases it will be possible for the driver to vary the setting via a cable or hydraulic system. Seven front and rear spring rates and five front and rear roll-bar settings are available. Dunlop have undertaken considerable tyre development for this car, which is likely to represent their most interesting involvement In motor racing this season. These Dunlop tyres, whether of dry-weather slick or wet-weather type, are of 325/625 x 16 in. at the front and 325/650 x 16 in. rear. They are mounted on alloy wheels made specially by the Kent Auto Castings division of GKN, resembling as closely as possible the optional production Jaguar alloy wheels—but they’re of 13J section at the front and 13.5J rear.
Electric windows are not the only trappings of luxury retained in this racing jaguar: Messrs Bell & Co. have power steering to save forearm effort. Apparently, this is an absolute necessity in order to turn those fat front tyres at all! Not surprisingly, Ralph Broad has considerably doctored the Adwest rack and pinion, developing new valving and quillshafts, building in progressive assistance, though he admits that at the moment his system is a mite too sensitive.
The interior of this racing Jaguar is in the best wood-veneer luxury tradition—the full facia and Smiths instrumentation is retained apart from the substitution of a chronometric tachometer. A superb Moto-Lita driver’s seat is fitted, paired with a Moto-Lita wheel, and a Williams full-harness. A glass-fibre replica rear seat will be fitted for racing, “to give the right image”.
The emergence of the racing Jaguars is a triumph of hard work and perseverance by Broad, who has campaigned within Leyland for just such a programme for three years. Eventually he was commissioned to develop the cars on September 9th last. The first plans were drawn on October 1st and the first metal cut on November 1st. The result is a five-month engineering achievement of true magnificence.
Reading between the lines, Broad hopes success this season will lead to participation in the Group 5 World Championship of Makes series next year with XJ-Ss, a model which is dimensionally ineligible for Group 2. He talks of twin-cams, four-valves per cylinder, 6.4-litres and 900 b.h.p. in unturbocharged form and a potential 1,500 b.h.p. with a turbocharger per 6-cylinder bank—”but I don’t agree with turbocharging for long distance racing.”
What was patently obvious amidst the shambles of the Leyland organisation at the Silverstone press preview was that if these Jaguars are successful it will be because of Broad, his mechanics and drivers and in spite of Leyland administration. The hiring of a high-calibre team manager must now be Leyland’s first priority; it needs a man of Neerpasch status to take on the might of Europe. Would Brian Redman retire from driving ?—C.R.