Jaguar V12 engine
| Jaguar V12 engine | |
|---|---|
 |
|
| Overview | |
| Manufacturer | Jaguar Cars |
| Production | 1971–1997 |
| Combustion chamber | |
| Configuration | 60° SOHC V12 |
| Chronology | |
| Successor | Jaguar AJ-V8 |
The Jaguar V12 piston engine was one of the premier powerplants of the 1970s and 1980s. It was first seen in the Series 3 Jaguar E-type of 1971 and was based loosely on an earlier design for an intended Le Mans car, the Jaguar XJ13. The V12 was only Jaguar's second engine design to go into production in the history of the company. The all-alloy block was fitted with removable wet liners and had a SOHC two-valve alloy head with flat block mating surface, and the combustion chamber in the piston crown carved in a shallow cup form.
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, which shared the same basic architecture of the XK cylinder head. After Jaguar withdrew from racing, the V12 designs lay forgotten until 1963 when Jaguar Cars purchased Coventry Climax and, as a result, Walter Hassan who designed the XK engine with William Haynes at SS Cars Ltd, rejoined the team together with Harry Mundy and Claude Baily.
The engine was re-examined as a possible powerplant for a return to Le Mans. After an extensive redesign by the team, the alloy block DOHC engine with fuel injection was born, and installed on the Jaguar XJ13 in 1966. After its racing aspirations were put on hold in 1967, the team 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 limousine, which was contemplated at the time.
The racing engine was extensively redesigned and the cylinder heads were replaced with a more conventional two-valve design, employing a SOHC acting directly on vertically inclined valves through bucket tappets, in a move that bore striking similarity to the cylinder head design of the contemporary Rover 2000, a similarity which is further noted in the use of a flat-cylinder head and dished 'heron' pistons of both engines. These changes greatly reduced complexity, weight, size and noise. The revised head design had restrictive and long 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 chain-driven 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 retired for a number of years before finally seeing production in the series III E-type in 1971.
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