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Jaguar XK—Straight-Six

One of the most iconic power plants in automotive history, Jaguar’s XK straight-six was light, powerful, reliable-and essentially unchanged for almost 40 years. As well as featuring in the original XK120, the unit was used in XK140, XK150, and E-type sports cars, C- and D-type racers, and several sedan ranges.


Before World War II, when Jaguar was known as SS Cars, engines had been bought in from rival company Standard. The idea that Jaguar should produce its own engine was born during the war. Led by company founder William Lyons, an engineering team including William Heynes, Walter Hassan, and Claude Baily planned the engine in minute detail while on fire-watch duty on the roof of Jaguar’s Coventry factory. Harry Weslake was brought in to create the crucial aluminum cylinder-head design. The XK engine finally freed the renamed Jaguar Cars from dependence on outside suppliers.



Dates produced1949-1986
ConfigurationFront-mounted, longitudinal
Engine capacities2.4 liter, 2.8 liter, 3.4 liter, 3.8 liter, and 4.2 liter
Power output133 bhp (2.4) to 265 bhp (3.8 and 4.2)
TypeConventional four-stroke, water-cooled, gas engine with reciprocating pistons, distributor ignition, and a wet or dry sump
Headdohc actuated by pushrod and rocker; two valves per cylinder
Fuel SystemTriple HD.8 SU carburetors
Bore and Stroke3.42 in x 4.17 in (87 mm x 106 mm)
Power260 bhp @ 4,000 rpm
CompressionRatio 9.0:1

Greater depth, more power

The cylinder head on Jaguar’s straight-six is especially deep to accommodate two large valves per cylinder. Larger valves allow more fuel-air mixture to be drawn into the cylinder, and make it easier for exhaust gases to be expelled. This improves the efficiency of the combustion process.


It is a quote. The Definitive Visual History Of The Automobile 2011

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