Jaguar V12 Engine - Development

Development

Initial designs for the V12 were produced as early as 1954, with a view to using it in a Le Mans car. The engine was to be a 5.0-litre, quad-cam engine with a high redline. After Jaguar withdrew from racing, the V12 designs lay forgotten until the early 1960s when they were re-examined as a possible powerplant for a return to Le Mans with the Jaguar XJ13. After its racing aspirations were put on hold in 1967, Jaguar considered the use of this quad-cam configuration for road use but it was judged to be too complex, large and heavy, as well as unacceptably noisy for a luxury car. The engine was extensively redesigned by Walter Hassan and Claude Baily and the cylinder heads were replaced with more conventional two-valve SOHC designs, reducing complexity, weight and noise. The revised head design had restrictive inlet ports which sacrificed top-end power but which, along with an increase in displacement to 5.3 litres, greatly improved performance at low-mid engine speeds, which was desirable in what was planned to be a heavy luxury car. The SOHC heads and the soft valve springs fitted to reduce valvetrain noise resulted in the redline being lowered to 6,500 rpm from the 8,000 rpm of the original quad-cam design. When the limousine project was cancelled the engine was again left for a number of years before finally seeing production in the series III E-type in 1971.