Each month ahead of the JCNA Championship Challenge this July in Franklin, TN, we take a look at the significance of each anniversary which makes 2001 and the Franklin event so significant. After looking at the 40th anniversary of what is probably the most recognized Jaguar of all time (see http://www.jcna.com/library/news/jcna0007.html), we focus this second part on the Jaguar V12 engine.

V12 … a badge which says a lot about the speed, the power and the performance of any motorcar... an engine configuration which is hard to top and considered the ultimate power plant in term of power and smoothness. While a few manufacturers have offered V12 power since WWII, two marques stand out when it comes to the ultimate engine. First is Ferrari, a V12 maestro for the large variety of V12 engine they designed, sometimes as small as 2 liters. Second, is Jaguar who in contrast only offered one V12 which would become the only mass production V12 since world war II and remaining in production for a quarter of century.

In the early 50s, as Jaguar was heavily involved in racing, engineers started work on a V12 racing engine designed to replace the XK engine and ensure Jaguar continued success at le Mans. At the time, the V12 project called for a 5 liter, dual overhead cam engine but it would end up being shelved when Jaguar announced its withdrawal from factory racing in 1956.

Ten years later, as Jaguar considered returning to Le Mans, work on a V12 race car started again and in 1964 a prototype 5 liter V12 ran for the first time. Still featuring dual overhead cam, which had become a Jaguar signature feature with the XK engine, and hemispherical heads, the engine produced just over 500 hp which was a little below the expectations of Jaguar engineers who were expecting close to 120 hp per liter or around 600 hp. Closely linked to the four cam V12, was the development of the race car which would receive the new engine, the XJ13, a mid engine, aluminum monocoque racer completed in 1966. Unfortunately, testing showed the car was not as competitive as it should be to represent Jaguar at Le Mans and the XJ 13 was never entered in the 24 hour classic.

In the meantime, Jaguar designers were working on an all new saloon, the XJ6, powered by the XK engine but which was to be available with a larger engine to match the needs of Jaguar’s primary market, North America. V12 powered luxury cars had been important before WWII and with V8 being the new norm in America, a V12 was seen as the next logical step, providing the performance and smoothness required by a luxury car. However, Jaguar was faced with the racing design of the V12 prototype which lacked low to mid range torque, a must in a luxury road car.

Enter Jaguar’s chief engineer Walter Hassan, who had been one the engineers involved in designing the XK engine right after the war. Hassan had returned to the company after 15 years at Coventry Climax where he designed numerous engines, including those powering Lotus and Copper race cars which won numerous races and world championships.

Hassan revised the V12 design by replacing the twin cam hemispherical heads by a single cam flat heads. This transformed the engine not only making it suitable for use in the new luxury road car but making it more simple and more economical both in production costs and tooling. For a while, Jaguar had even considered producing both versions of the V12 but then decided not to because of the cost involved and in 1968, after Sir Lyons himself test drove both versions fitted in existing test cars, a final decision was taken to produce the single cam engine.

In production form, the all aluminum V12 engine developed a gross 320 bhp from 5.3 liters (or about 280 hp net), fed by four Zenith Strombergs side drafts carburetors. Firing 12 plugs at the proper time is far more complex than it is on a 6 or even 8 cylinder engine and at high RPM, points wouldn’t be able to handle the task. To solve the problem, ignition was a new Lucas OPUS electronic system which had successfully been used on Formula One engine. Compression was initially set at 10:1, this would drop to 9:1 for European spec models and only 7.8:1 in US models.

History repeats itself, and it was also decided that the V12 engine would be first launched in a sports car before finding its way under the bonnet of the saloon it was intended for. Just as in 1948 when the XK engine was presented to the world in a new sports car only intended at the time for minimal production… At the same time, Jaguar’s sports car, the E-type, was starting to loose its punch with more stringent emission control requirements. The 150 mph super car of 1961 was now barely able to reach 130 mph, as the horsepower of it’s engine had dropped from 265 hp to barely 200 hp… Fitting the V12 to the E-type was seen as the logical choice and, just like with the XJ6, the original plan was to offer the V12 as an option. This idea was quickly dropped and in fact only three 6 cylinder series 3 E-types were ever produced in 1971.

The launch of the V12 powered E-type didn’t go as smoothly as planned. Originally, the car was to be unveiled at the Geneva motor show in March 71 with the help of the XJ13 race car acting in a supporting role to showcase the race roots of the V12. But a few weeks before, on January 20th, the XJ13 prototype was almost destroyed in a high speed crash while shooting a promotional film, luckily Jaguar’s test driver Norman Dewis walked away from the crash.

Plans for the unveiling of Jaguar’s first V12 powered car were revised and a North American launch took place in Palm Beach FL, on march 25 1971, in presence of Sir Lyons himself, his last visit to America before his retirement the following year. While the series 3 E-type would only remain in production for 3 years, its role in launching the V12 would indirectly last for a quarter of a century.

1972 would see the launch of the XJ12, an XJ6 saloon powered by the V12 engine which would be available in a longer wheelbase version and also as a 2 door coupe, a model which would be dropped within three years to make room for the all new XJS. With the XJ12, Jaguar had set new standards for luxury cars, especially in North America, and while the venerable Le Mans winning XK in line 6 engine would remain the most popular choice, the V12 helped building Jaguar reputation.

Despite the all new engine under it’s bonnet, the E-type started showing its age and by 1973 / 1974 luxury car buyers demanded more comfort and features which the E-type lacked. Once again Jaguar created the surprise in 1975 by unveiling a radically different Grand Tourer, the XJS, powered by the same V12 engine the E-type helped launch 4 years earlier. One major change in 1975 was the introduction of the Bosh D Jetronic Electronic Fuel Injection system. While Jaguar engineers has considered using fuel injection on the V12 E-type, the system at the time was not fully ready especially when it came to dealing with emission control, forcing them to adopt the 4 carbs setup and air injection in the exhaust ports.

While the 70s had started with performance and horsepower being the selling point, the oil crisis of 1973 reversed that trend and fuel economy became critical. As years went by, the V12 engine suffered from its own thirst to the point when in the early 80 sales of the XJS had reached critically low level which could barely justify keeping the car in production.

Fortunately, the V12 and the XJS were saved by the work of a Swiss engineer, Michael May, who had developed the Fireball combustion chamber. Other auto manufacturers had considered his approach but only Jaguar found significant advantages and applied it to its engine. The Fireball combustion chamber introduced a turbulent swirling action thru various changes in the air flow allowing better combustion. The pistons were changed to a flat design and compression went back up to as high as 12:1. The main benefit from the changes was fuel economy with mileage going up by as much as 20% and Jaguar appropriately named it XJS HE, for High Efficiency, starting with 1981 when the new model was launched.

Little changes would take place over the rest of the 80s except for updated ignition and fuel injection systems with Lucas Digital EFI and Marelli ignition.

On track, the Jaguar V12 engine would turn out to be a success in various forms of racing. Early on in the US, Bob Tulius and his Group 44 team raced the V12 E-type to various victories and the 1975 championship in SCCA. After switching to the XJS, Tulius won many races in the Trans Am series and won the championship in 1977 and 1978.

In Europe, after a V12 powered XJ12C effort struggled with reliability problems, Tom Walkinshaw’s TWR Racing challenged the dominant BMWs in the European Touring Car championship, winning the title in 1984 and 1985. Tom Walkinshaw would also become the main architect of Jaguar’s World Sports Car Championship title in 1987, winning Le Mans in 1988 and 1990, and the Daytona 24 hours in 1988. All powered by racing version of the V12 engine, up to 7 liters.

The latest and most potent road going version of the V12 also came out of a TWR / Jaguar partnership with the XJR-S special series launched in 1989 to celebrate and capitalize on the 1988 win at le Mans. In the XJR-S, the V12 had been enlarged to 6 liters and developed 318 hp. In addition to continuing service in the Sports / GT Jaguar cars, the V12 remained the top of the line engine in the saloon line up to as late as 1996 in all the various body styles offered by Jaguar. From the original series 1 XJ12 to the latest X300 body style, the V12 engine powered Jaguar’s finest luxury cars for 25 years.

Open the bonnet of a 1996 XJ12 next to a 1971 E-type and it first seems that they have nothing in common. Look deeper though and the architecture looks similar, and soon you will find the (almost) same block.  For the general public, with limited knowledge of Jaguar offerings, the V12 engine is what they often remember the most. How many time when someone approaches you about your car do they ask : “is that a V12 under the hood ?”

See you in Franklin !

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About the author - Pascal Gademer is the webmaster and newsletter editor of the South Florida Jaguar Club. Owner of a restored and upgraded (for reliability and performance) 1972 series 3 E-type 2+2, he doesn't miss an opportunity to drive his E-type to various events (concours, rallies,..) often regardless of distances. His daily driver his another Silver Coupe, a 2000 XKR.

Posted: 4/2001