‘ Road cars powered by the XK were becoming known for their performance, smoothness and class’
Stately looking these days, but the Jaguar MkII powered by the 3.8-litre XK was a formidable and fast car. It was favoured by bank robbers, and consequently the police too
‘ Road cars powered by the XK were becoming known for their performance, smoothness and class’
Alongside the first‘ A-Type’ head of the early car came the‘ B-Type’ with a 35 ° angle for both sets of valves. Both of these heads featured a curved inlet port said to have been designed to improve swirl within the air going into the engine to aid fuel distribution and flame propagation. A straight port head was also developed and fitted to the 3.4. Along with the different heads came new carburettor setups: the original twin SUs, triple SUs and Weber side draughts.
These new cylinder heads and carb combos, and the variety of different performance figures they produced, helped differentiate the Jaguars they were fitted to, which included the sports cars – the XK 120 and 140 SE and M, and the 150 and 150S – and the big saloons, the MkVII and MkVIII.
In 1955 Jaguar’ s new small saloon was initially fitted with a smaller version of the XK straight-six. Its 76.5mm stroke allowed for a shorter, and therefore lighter, block. An 83mm bore gave it a capacity of 2483cc, but rather than round up, Jaguar named the engine, and the new car, the 2.4. With twin Solex carburettors, the 2.4 had 112hp. It wasn’ t long before Jaguar upped the power of its more compact saloon and, in 1957, it installed the 3.4 six under its bonnet. Jaguar also changed the name of this saloon to the MkII. Using the same short block, a 2.8 with an 86mm stroke was launched in 1968.
While these road cars were becoming known for their performance, smoothness and class, the 3.4 XK was to make a more rowdy impact in racing. Firstly, in the C-Type, it produced over 200hp and helped propel the Jaguar to win the 24 Hours of Le Mans in 1951 and 1963. The 3.4 was then employed in the D-Type, which also won Le Mans in 1955 and 1956. In 1957, a later 3.8-litre version not only finished first and second in the daylong French endurance race, but filled five of the six top spots.
It wasn’ t just an increase in capacity that helped these motors win races; wide-angle heads – often called the 35 / 40 head, where the numbers relate to valve angles – and dry sump lubrication systems pumped up power and, just as importantly, reduced the engine’ s dimensions to help create more slender aerodynamic bodies.
The success of the C-Type and D-Type in competition – plus the desirability of the latter’ s road-going spinoff, the XKSS – paved the way for Jaguar’ s most significant car. Its icon, the symbol of Sixties Britain, England’ s flagship motor: the E-Type. The new and achingly beautiful sports car was
As the Roadster or Fixed-Head Coupé, the E-Type was beautiful and fast – the fastest car in the world at launch
22 The Engine Rebuilder Issue 06