MODIFIED XJ12 6.0
Power struggle
It might look largely standard but this Series 3 XJ12 has a startling pace thanks to a 6.0-litre TWR engine
IT’S NOT often that I giggle when testing a classic car – it’s crucial and important work, I take my job seriously. But when I give the throttle of this XJ12 Series 3 the beans, causing the car to rush forward with a forcefulness I wasn’t expecting, I can’t help but give an involuntary laugh at the absurdity of the experience.
The reason behind this mirth-creating acceleration is the TWR-developed 6.0- litre V12 under the bonnet of this largely standard-looking car. Over 30bhp more power than its original 5.3 version has given the car an unexpected performance, one that I find both addictive and also hilarious. Other than being built in 1990, making it a reasonably late example of the Jaguar XJ12 Series 3, little is known about the car’s early years. Sometime In the mid-’90s it was sent by the then owner to the still burgeoning Jaguar specialist, JD Classics in Maldon, Essex, for an engine swap. Out came the original 5.3 V12 and in went a 6.0-litre of the sort that had been independently produced and developed by Jaguar’s former competition and tuning partner, Tom Walkinshaw Racing.
In 1984 and as a way to cash in on its successes competing in the European Touring Car Championship with the XJ-S, TWR began offering a series of factoryapproved modifications for the standard road car plus the XJ Series 3 and later the XJ40 through its JaguarSport brand. The styling updates included handsome 15in Speedline alloys, a discreet body kit and a replacement TWR-designed steering wheel. Mechanically, there were stiffer front springs, specially valved Bilstein dampers all round, rear radius arm front bushes that were 20 percent less compliant than standard, stiffer steering rack mountings and revised power steering offering more feel. There was also a ‘Quick Shift’ version of the three-speed automatic or a close ratio five-speed manual gearbox conversion.
The ultimate modification, though, was TWR’s own 6.0-litre version of Jaguar’s venerable 5.3-litre V12 engine, the extra 648cc obtained courtesy of a longer-stroke crankshaft (78.5mm instead of 70mm). Aided by Zytek sequential injection, a digital ignition system and modified cold air intakes, power was lifted from the standard unit’s 285bhp to 318bhp.
Admittedly at £6745 in 1985, TWR’s 6.0-litre was an expensive way to gain just 33bhp, costing over £500 more than a new Ford Fiesta XR2. But due to its responsiveness and improved torque, the critics were still impressed by the unit. “Hit the open stretch of clear road and nail the throttle,” said Road & Track magazine in its August 1985 issue when it tested a JaguarSport-modified XJ-S, “and the Jag takes off like a scalded cat, cove
