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The Jaguar V12 - Part One - Origins

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

For 25 years, between 1971 and 1996, Jaguar’s smooth and  refined V12 power unit powered the Series 3 E-Type as well as a range of luxury saloons. Right from the outset the engine was designed with enormous tuning potential reserves and, in racing form, powered cars such as the Le Mans winning TWR prototype racers. Its tuning potential was taken to extremes in the world of offshore powerboat racing as well as drag racing.

 

Of course, the production V12 engine was not a new idea – the first production use of a V12 was as early as 1915 in Packard’s “Twin Six”.

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

Other manufacturers such as Fiat (7 litre V12) and Daimler (“Double Six) followed. V12-equipped cars soon proliferated and offerings were available in America from Auburn, Cadillac, Lincoln, Packard and Pierce-Arrow. The Germans followed suit with the Horch and Maybach. In 1930 Tatra of Czechoslovakia offered a 6 litre side-valve V12.

 Packard’s 1915 “Twin Six”

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

Tatra's T80 V12 of 1931
(65 degree; 5.99 litres)

One thing all these cars shared was the association with “refinement” and “luxury” that a V12 configuration offers. This reputation was further enhanced by Hispano-Suiza’s use of a 11.1 litre V12 and Rolls-Royce’s 7.3 litre Phantom III. Early engines tended to have push-rod actuated valves although, just before hostilities commenced in 1939, W.O. Bentley designed a high-revving 4.4 litre for Lagonda with valve-gear very similar to the later Jaguar’s. Since 1945, the V12 became associated with quality Ferraris, Lamborghinis and Maseratis – especially in racing applications.

 

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

Jaguar’s Walter Hassan (Chief Engineer – left) and Harry Mundy (right)

Jaguar’s V12 does have the distinction of being the first British manufacturer to emerge from WW2 with the first British V12. But why did Jaguar choose the V12 configuration? According to Walter Hassan, OBE and Harry Mundy, both credited with Jaguar’s V12, said the V12 layout gives perfect balance which allows high-speed running and the power potential which accompanies this.

At the time, this was an important step for Jaguar. They invested over £3 million in tooling for mainstream manufacture of their engine – without an “economy” model to fall back on if the world decided that large capacity V12 engines were not the way forward. It is no coincidence that, early on in the V12 prototype project, alternate configurations such as a V8, slant-6 and straight-4 designs were trialled.

Jaguar had first considered a V12 as early as the 1940s. Claude Baily realised that a replacement for the 6-cylinder XK engine would eventually be needed – particularly if Jaguar were to continue their racing successes in the face of fierce competition from Ferrari and Ford.

In 1964, a first formal “Instruction To Proceed” was issued giving the go-ahead to build a number of V12 prototype engines. A second instruction was given in April of 1965 by Claud Baily for this engine to be installed in the planned prototype Le Mans racecar – the XJ13. In June of 1965 a further “Instruction To Proceed” was issued for construction of the XJ13 itself. The plan was to develop and install this engine in the XJ13 with the aim of repeating their successes at Le Mans in the 1950s. The emphasis of this V12 engine project was very much on racing from the outset – with the possibility of a production engine arising from this experience.

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

“Instruction To Proceed” © Jaguar Heritage

The first of these engines (engine “number one”) was assembled in July 1964. In common with all previous Jaguar projects, the prototype V12 project was given an internal code. The code for this project was “XJ6” – not to be confused with the later car of the same name!

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

 

XJ6 Project - Engine Log

Conducted in great secrecy, Jaguar’s Competitions Department and Engine Development Department kept meticulous records for each of the engines built, developed and tested. Thanks largely to the efforts of Jaguar Heritage, many of these records have been preserved and safely archived. The detailed log books for all but one of these “XJ6” engines survive (although the “missing” log book may, in fact, be for an engine that never existed as a complete engine). The first prototype V12 was assembled in July of 1964 (engine number one).

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkXXJ6 Project - Engine Log © Jaguar Heritage

In total, it is believed that six complete engines were assembled as part of the XJ6 project. One of the six was assembled using a cast iron block (engine number four – not believed to have survived testing) although the remainder were cast alloy. It was common practice within Jaguar in the 1960s to scrap engines and components when no longer needed and, of this original six, it is believed that only four survive today. Two of these engines (numbers one and seven) remained with the XJ13, one had a privileged existence following extended development (number two) and one was built up from a collection of new and used spare parts long after the project had ceased (number eight).

In summary, the four surviving engines’ histories are as follows:

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkXJaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkXJaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

All these engines were initially assembled with dry sumps and duplex chain drive to the camshafts. The only exception was engine number one that had a gear-driven camshaft arrangement fitted after the XJ13 development had pretty much ceased – this modified engine was fitted to the XJ13 as late as 1978 by which time the car was only wheeled out for demonstration runs etc. For all of its active development life, the XJ13 was powered by engines with duplex chain drive. 

Jaguar, Mk10, 420G, tera, V12, quadcam, Building The Legend, Jaguar Mk10, MkX

The engine blocks themselves were cast by the West Yorkshire Foundry. The foundry on Clarence Road Leeds started production in the 1930's; its closure was announced in September 2003.

The blocks were machined by Coventry Climax and returned to Jaguar for assembly. The Coventry Climax company has its roots in 1903. In 1950 Walter Hassan joined them and designed the FWA, a feather weight engine for automobiles. The first Coventry Climax racing engine appeared at the 1954 Le Mans 24 Hours in the back of a Kieft. The engine became popular in sportscar racing and it quickly became the engine to have in F2. Coventry Climax was purchased by Jaguar only one year before the quad-cam V12 project – bringing Walter Hassan to Jaguar where his talents were further exploited.

The engine logs give information on exactly how each engine was assembled as well as their detailed development history on both the test bed and when fitted to cars. The logs also refer to a number of technical reports – many of which survive in the Jaguar Heritage archive. Practically every engine component was individually coded and it is possible to trace their movements from one engine to another during development.

To be continued …..

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