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{{Infobox Automobile engine
|image=[[Image:Jaguar XK6 engine.jpg|250px|Jaguar XK engine in an E-Type; the large polished aluminium rocker covers show this is a DOHC design]]
|name=Jaguar XK
|manufacturer=[[Jaguar Cars]]
|production=1949&ndash;1993
|class=[[DOHC]] [[Straight-6|I6]]
|successor=[[Jaguar AJ6 engine|Jaguar AJ6]]
}}
[[Image:1955 Jaguar XKD engine.jpg|right|thumb|250px|Jaguar XK engine in a 1955 [[Jaguar D-Type]]]]
[[Image:SC06 Jaguar XK150 engine.jpg|right|thumb|250px|XK6 engine in an [[Jaguar XK150|XK150]]]]

The famed [[Jaguar (car)|Jaguar]] '''XK''' engine was introduced in 1949 and produced until 1993.  It was a [[DOHC]] [[inline-6]] engine. The 4.2 variant was also used in some military vehicles with very few modifications.

==3.4==

The first use was in the 1949 [[Jaguar XK120]], where it was billed as the 3 1/2 litre. This was a 3.4 L (3442 cc) version with an 83 mm bore and 106 mm stroke. It had an iron block and an aluminum cylinder head which delivered {{Auto bhp|160|0}} at a compression ratio of 8:1, rising to {{Auto bhp|210|0}} with the C-Type head as raced at Le Mans. A 4-cylinder '''XK''' variant was never produced.

This engine was used in the following cars:
* [[Jaguar XK120]]
* [[Jaguar XK140]]
* [[Jaguar XK150]]
* [[Jaguar XKSS]]
* [[Jaguar Mark VII]]
* [[Jaguar Mark VIII]]
* [[Jaguar Mark 1]]
* [[Jaguar Mark 2]]
* [[Jaguar Mark 2|Jaguar 340]]
* [[Jaguar S-Type (1963)|Jaguar S-Type]] (original)
* [[Jaguar C-Type]]
* [[Jaguar XJ6]]

==3.8==

The larger 3.8 L version was released in 1958.  It was fitted with sleeves and bored to 87 mm and produced up to {{Convert|265|hp|kW|0|abbr=on}}.  

This engine was used in the following cars:
* [[Jaguar XK150]]
* [[Jaguar Mark 2]]
* [[Jaguar Mark IX]]
* [[Jaguar Mark X]]
* [[Jaguar E-Type]]
* [[Jaguar S-Type]] (original)
* [[Jaguar D-Type]]
* [[Panther J72]]

==4.2==
The 4.2 litre version was officially released in 1965, though racers had been boring the 3.8 out all the way to 4.2 litres for years.  The block was an all new Siamese sleeves design. The official bore was 93 mm, and the engine produced from 170 hp (DIN) with [[Zenith Carburetters|Zenith-Stromberg]] carburettors, to {{Convert|265|hp|kW|0|abbr=on}} hp (claimed) with the triple [[SU carburettor|SU]] HD8 carburettors. This form of the XK Engine has been praised by many and notably [[Gunnar Heinrich]]: "Big, noisy and inefficient; those engines were great.", although in contrast to BMW [http://en.wikipedia.org/wiki/BMW_340] and Mercedes [http://en.wikipedia.org/wiki/Mercedes-Benz_W186] engines of the same generation the XK engine was relatively unstressed and high torque with far more advanced camshaft configuration. In stark contrast, [[Jeremy Christian]] stated in 'The Allure of the Big Cats: Cougar, Jaguar, Panther ([[2006]])': "I commend Jaguar on the production of an engine with such musical qualities, but enough is enough! It's an engine: not a symphony. It's British: not Italian." He does, however, praise the improved 6.0L [[V12]]: "...cloaked in the bodywork of an XJ-S it [the 6.0 V12] forms a marriage between form and function akin to the bar set by the Germans but in a package that can be nothing other than what it is: A Jaguar. To quote from a 1980s TWR Jaguar brochure: 'the powerful roar of the engine states that you are not coming; you have arrived." In truth, the 4.2 XK engine was poorly finished from the factory with the heads not being flowed and the gaskets too small for the gap. Privately, these engines make excellent bases for some modifications achieving approx. 220bhp and much more torque just by flowing the head.

This engine was used in the following cars:
* [[Jaguar Mark X]]
* [[Jaguar 420]]
* [[Jaguar Mark X|Jaguar 420G]]
* [[Jaguar E-Type]]
* [[Jaguar XJ6]]
* [[Jaguar XJ6 Sovereign]]
* [[Daimler Sovereign|Daimler Sovereign]]
* [[Daimler DS420|Daimler DS420 Limousine]]
* [[Panther J72]]
* [[Panther De Ville]]

It was also used in the following military vehicles:
* [[FV101 Scorpion]], a British CVR(T)
* [[FV107 Scimitar]], a British Armoured car.

The 1987 [[Jaguar XJ6]] was the last [[Jaguar (car)|Jaguar]] car fitted with the XK6 engine. In 1992 the last [[Daimler Motor Company|Daimler]] DS420 Limousine was produced. Like all other DS420 limousines, it was equipped with a 4.2L XK6 engine.

The amount of time the 4.2 XK engine has remained in production means it has the rare accolade of having been in service in cars spanning 6 consecutive decades.

==2.4==

The 2.4 was a de-stroked (to 76.5 mm) version of the 3.4, and produced {{Convert|133|hp|kW|0|abbr=on}}. It featured Solex downdraft carburettors in the original Mark I and Mark II saloons.

This engine was used in the following cars:
* [[Jaguar Mark 1|Jaguar 2.4 Mark I]]
* [[Jaguar Mark 2|Jaguar 2.4 Mark II]]

The [[Jaguar Mark 2|Jaguar 240]] was fitted with an uprated version of that engine, incorporating the straight-port cylinder head and twin SU carburettors.

==2.8==

A 2.8 version was introduced for the entry-level XJ6 models in 1968 and remained available until replaced by the 3.4 in 1975. 

This engine was used in the following cars:
* [[Jaguar XJ6|XJ6 Series I]]
* [[Jaguar XJ6|XJ6 Series II]]
* [[Daimler Sovereign|Daimler Sovereign]]

==See also==
* [[Jaguar AJ-V6 engine]]
* [[Jaguar V12 engine]]
* [http://www.jagweb.com/aj6eng/xk_performance.html XK Performance]

[[Category:Jaguar engines|XK6]]
{{Jaguar}}