Jaguar XK6 engine
Encyclopedia
BMW 340
The BMW 340, subsequently rebadged as the EMW 340, was a large six cylinder four door passenger saloon produced at Eisenach initially in the name of BMW. Five door 340 station wagons were also manufactured...
and Mercedes engines, the original XK engine was relatively unstressed and produced high torque thanks to its more advanced valve and head configuration.
Early development
Prior to World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, SS Cars
SS Cars Ltd
SS Cars Ltd was a British car maker. It grew out of the Swallow Sidecar Company and was first registered under the new name in 1934. Some conjecture to the origins of the SS name exist, It was John Black who when asked the meaning of SS said it has always stood for Standard Swallow...
(as Jaguar was then known) used engines produced by the Standard Motor Company
Standard Motor Company
The Standard Motor Company was founded in Coventry, England in 1903 by Reginald Walter Maudslay . The Standard name was last used in Britain in 1963, and in India in 1987.-1903–1914:...
; a 1.5 litre 4-cylinder and two 6-cylinder engines of 2.5 and 3.5 litres. Sir William Lyons and his engine designers; William Heynes
William Heynes
William Munger Heynes , born in Leamington Spa, was a British automobile engineer.Heynes was educated at Warwick School from 1914 to 1921 before joining the Humber Car Company in Coventry in 1922 where he worked in the drawing office before becoming head of the technical department in 1930...
(Chief Engineer), Walter Hassan
Walter Hassan
Walter Hassan OBE, C.Eng., M.I. Mech.E. was a distinguished UK automotive engineer who took part in the design and development of three very successful engines: Jaguar XK, Coventry Climax and Jaguar V12 as well as the ERA racing car....
and Claude Baily, are widely reported to have discussed a new range of engines to replace the pre-war Standard based units whilst fire-watching on the roof of the Jaguar factory during World War II and to have developed prototype engines immediately after the war. In fact, Jeff Daniels has demonstrated that Jaguar’s wartime engine developments went far beyond mere discussion and design, extending to the construction and testing of several prototype engines from as early as 1943.
The initial aim was to produce a series of engines of higher than normal output that would be able to stay ahead of the competition without revision for many years and which Sir William insisted also had to "look good". In 1942-43, a range of configurations was considered and it was concluded that, for good breathing and high bmep, the new engines would need vee-opposed valves operating in hemispherical combustion chambers. Two configurations of this type were selected for comparison in 1943 and the prototypes named "XG" and "XF". The XG 4-cylinder of 1,776 cc, first tested in October 1943, was based on the 1.5 litre Standard block and used its single cam-in-block to operate the opposed valves via a complicated crossover pushrod arrangement, similar to that of the pre-war BMW 328
BMW 328
The BMW 328 is a sports car made by BMW between 1936 and 1940, with the body design credited to Peter Szymanowski, who became BMW chief of design after World War II ....
. The XF 4-cylinder of 1,360 cc used the now familiar dual overhead cam (DOHC) configuration and was first tested in November 1944. The XG was found to suffer from excessive pushrod and rocker noise and gas flow figures through its vertical valve ports did not equal those of the horizontal ports on the XF. Therefore, from these two options, the DOHC XF layout was selected and by October 1945 a larger DOHC 4-cylinder of 1,996 cc called the "XJ" began prototype testing and underwent many changes as its head, ports, valve gear and camshaft drives were perfected.
By September 1947 a 3.2 litre 6-cylinder version had been produced, called the "XJ 6-cylinder", which was intended to replace both Standard-based 6-cylinder units. Testing showed the need for higher torque at low speeds than this engine could produce and hence it was 'stroked' to form the "XK 6-cylinder" which, with its initial capacity of 3,442 cc, was settled upon for production in 1947-48. This engine first powered the Jaguar XK120
Jaguar XK120
The Jaguar XK120 is a sports car which was manufactured by Jaguar between 1948 and 1954. It was Jaguar's first sports car since the SS 100, which ceased production in 1940.-History:...
, followed by the Jaguar Mark VII
Jaguar Mark VII
The Jaguar Mark VII was a large four-door sports sedan launched by Jaguar Cars of Coventry at the 1950 London Motor Show. It replaced the Jaguar Mark V, but as there was a Bentley Mark VI already on the market, Jaguar decided to call the next model Mark VII...
and a number of other Jaguar models in subsequent years.
The XG prototype soldiered on as a component testbed until 1948. There also existed an "XK 4-cylinder" of 1,790 cc, also first tested in October 1945 and remaining under development alongside the XJ and XK 6-cylinder units. At the time of William Heynes' paper presented to the IMechE in February 1953, the XK 4-cylinder was still referred to as being under development. It was only finally dropped as a possible production engine later in 1953, by which time it had been realised that Jaguar's image in the market had moved beyond the need for a replacement for the old 1.5-litre Standard 4-cylinder unit.
Because the 6-cylinder XK prototypes were found to be so much more refined than the 4-cylinder versions, in 1951 a 1,986 cc 6-cylinder version of the XK 6-cylinder was built to see if it would suffice as a smaller scale engine. By 1954 this had grown to 2,483 cc and it was this short-block version of the XK 6-cylinder that was fitted to the new compact Jaguar 2.4-litre (retrospectively known as the Mark 1) released in that year. None of the 4-cylinder prototypes ever advanced to production.
In his book, Jeff Daniels claims he could not find confirmation among the Jaguar archives that the 1,996 cc version of the 4-cylinder was called "XJ" but William Haynes' paper presented to the IMechE in 1953 makes it clear that this was indeed the name given to that prototype. The same paper does not mention the short-block XK 6-cylinder which by then was well into its development for the 2.4-litre of 1954. Instead, the paper refers somewhat misleadingly to both the 1,996 cc XJ 4-cylinder (clearly as an experimental engine) and the XK 4-cylinder, the latter being referred to in guarded terms, not declaring the engine's capacity and stating ″at the present full details cannot be given as the engine has not yet been released to the market″.
Thus were developed the two block sizes that formed the basis of all subsequent XK 6-cylinder engines; the shorter block being used for the 2.4 and 2.8-litre engines and the full sized block for both versions of the 3.4, the 3.8 and the 4.2-litre engines.
Valve train
Visually the most recognisable aspects of the XK engine are the dual cam covers atop the engine, which were polished alloy until a change to ribbed black and alloy finish soon after the arrival of the 4.2 litre versions in 1966. The unusual depth of the engine's cylinder head was dictated by the desire to make room for two generously sized valves whilst not excessively restricting the flow of gases into and out of the hemispherical combustion chambers. To satisfy these two conditions, a relatively wide angle between the valves was initially chosen, with quite long valve stems. To efficiently operate valves whose tops were such a long way apart, the dual overhead cam arrangement was found to be the most effective.The cam lobes act directly on bucket type tappets, which are adjusted by means of shims between the underside of the bucket and the top of the valves. Two duplex chains drive the camshafts, one from the crankshaft to a sprocket at the level of the combustion chambers and one from the sprocket to each camshaft. The original sprung slipper design of the lower cam chain tensioner proved to be too weak and after a couple of years was changed to hydraulic operation.
Cylinder head
The cylinder heads were made of RR50Hiduminium
The Hiduminium or R.R. alloys are a series of high-strength, high-temperature aluminium alloys, developed for aircraft use by Rolls-Royce before World War II. They were manufactured and later developed by High Duty Alloys Ltd....
aluminium alloy due to that material's high rate of heat conduction and light weight, the latter estimated by Bill Heynes to give a weight saving of some 70 lb (31.8 kg) compared with a similar head made of cast iron. Special attention was paid to the gas flow, with Harry Weslake
Weslake
Weslake Research and Development was founded by Harry Weslake, with premises in Rye, East Sussex, England. Weslake was a cylinder head specialist who had been instrumental in modifying the side valve standard engine used in the first SS sports car. He also worked on the larger SS engine: "The...
designing a curved inlet port to impart swirl to the air-fuel mixture for improved combustion. The same basic cylinder head layout was preserved throughout the production life of the engine but with many detail changes. Valve and port sizes and angles, camshaft lift, compression ratio and carburetion were frequently amended from model to model, depending upon whether power or torque was being emphasised. Very early XK engines fitted to the XK 120 sports car and Mark VII saloon lacked fixing studs at the front part of the cam covers, where they covered the timing chains, which leaked oil as a result. From 1951 onwards, all XK engines had studs around the full perimeter of the cam covers.
The earliest cylinder heads are known as "Standard" or "A type" heads and are identifiable by their differing valve angles of 30 degrees inlet and 45 degrees exhaust, as well as by their unpainted aluminium finish. Around 1954, the "B type" head appeared, with equal valve angles of 45 degrees on inlet and exhaust. The "B type" heads are painted light "duck egg" blue (early cars) to light green (later cars) in the 2.4 and 3.4-litre models and metallic dark blue in 3.8-litre models. A very few XK 120s and XK 140s were supplied to customers with the "C type" cylinder head, which was painted red and carried a plaque on each cam cover stating "Jaguar Type C".
A supposedly more efficient "straight port" cylinder head was introduced later in the 1950s and this was painted pumpkin orange on the XK-150S. The cylinder heads in the Series 1 E-type and Mark X were painted gold whether the engine was a 3.8-litre or 4.2-litre. With the advent of the Series 2 E-Type and 420G, around the same time as the arrival of the ribbed cam covers, the practice of painting the cylinder heads ceased. Many sources still describe the subsequent unpainted aluminium finish as "silver".
The logic behind Jaguar's colour coding of its cylinder heads of the late 1950s and early 1960s can be difficult to fathom and sources often get it wrong. It can be determined from Heiner Stertkamp’s reference that the colour-coding follows the pattern listed below. The only real anomaly is that the earliest 3.8-litre E-Types had an orange painted head (because they had 3 carburettors) but later changed to gold (because they had straight-port heads). Gold paint signified a straight port triple-carburettor setup from then until the demise of the Mark X.
- Red => 3.4-litre with C-type head and 2 carburettors (XK 120 C and XK 140SE/M only)
- Light duck egg blue and later light green => 3.4-litre with B-type head and 2 carburettors (may appear as light blue, light green or light blue-green)
- Dark blue metallic => 3.8-litre with B-type head and 2 carburettors
- Orange => 3.4 and 3.8-litre with B-type head and 3 carburettors AND earliest 3.8-litre with straight-port head and 3 carburettors
- Gold => later 3.8-litre and all 4.2-litre (until 420G and Series 2 E-Type) with straight-port head and 3 carburettors
Cars with the straight-port head and only two carburettors did not have painted heads. See the complete table of XK cylinder head types as they relate to Jaguar and Daimler models at the end of this article.
Engine block
The block was made of cast iron (with the exception of some made of aluminium alloy for racing engines), with the crankcase split on the centreline of the seven-bearing crankshaft. The crankshaft was made of EN16 steel, heat treated prior to machining. A new innovation was the fitting of a proprietary Metalastik vibration damper on the nose of the crankshaft to eliminate damaging crankshaft resonances. The design and materials of the bottom end of the engine hardly changed throughout its life, apart from the changes dictated by the respaced cylinders of the 4.2 litre version (also used by the 'new 3.4' litre version). The oil pump was changed after a couple of years from a relatively inefficient gear-type pump to a Hobourn-Eaton eccentric-lobe unit.Fuel system
The pre-injection cars had either two or three SUSU Carburetter
SU Carburetters were a brand of carburetter usually of the sidedraught type but downdraught variants were used on some pre-war cars....
, Weber
Weber carburetor
Weber is an Italian company producing carburetors, currently owned by Magneti Marelli Powertrain S.p.A., in turn part of the Fiat Group.The company was established as...
, Zenith or Zenith-Stromberg carburettors
Zenith Carburetters
Zenith Carburetters was a British company making carburettors. In 1955 they joined with their major pre-war rival Solex Carburettors and over time the Zenith brand name fell into disuse...
of various sizes depending upon the model and market. The first engines to receive fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....
were some D-Type sports racing cars but fuel injection did not become available on the road cars until 1978. The US market was the first to receive fuel injection on certain models, with the switch away from carburettors eventually extending across the range and to all markets.
Power rating
Readers should note that during the 1950s and 60s Jaguar used the SAE gross horsepower measurement system used by US manufacturers, as otherwise Jaguar cars would have appeared under-powered in comparison with US cars which always quoted their horsepowerHorsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
using the SAE gross system. Gross horsepower was flattering since non-standard exhaust systems were allowed and most of the usual belt-driven ancillaries were removed or discounted from the horsepower calculation. This was superseded by the more realistic SAE net horsepower system around 1972, although Jaguar power ratings of that era may also be expressed using the very similar DIN net rating system. An objective comparison of the power outputs of the various models of XK6 powered Jaguar is therefore quite problematic.
3.4-litre
The first production use of the XK 6-cylinder was in the 1948 Jaguar XK120Jaguar XK120
The Jaguar XK120 is a sports car which was manufactured by Jaguar between 1948 and 1954. It was Jaguar's first sports car since the SS 100, which ceased production in 1940.-History:...
, which used the 3.4 L (3,442 cc / 210 cu-in) version with an 83 mm (3.3 in) bore and 106 mm (4.2 in) stroke. It had an iron block and aluminium cylinder head with no bore liners. It had a wider gap between cylinders 3 and 4 than between the other cylinders. The 3.4 was first rated at 160 bhp SAE gross at a compression ratio of 8:1, rising to 210 bhp SAE gross with the C-type cylinder head (confusingly not the head from the C-Type as raced at Le Mans) all the way to 265 bhp SAE gross with the “straight port” head at a compression ratio of 9:1 as fitted to the XK150SE.
Almost as soon as the new compact Jaguar 2.4-litre (described below) was released, there was pressure on Jaguar to fit the 3.4 litre engine to it. This was duly done in February 1957, the car being known as the Jaguar 3.4-litre. The designation “Mark 1” for these cars was applied retrospectively, after the release of the Mark 2 in 1959.
The original 3.4 litre XK6 was used in the following road cars:
- Jaguar XK120Jaguar XK120The Jaguar XK120 is a sports car which was manufactured by Jaguar between 1948 and 1954. It was Jaguar's first sports car since the SS 100, which ceased production in 1940.-History:...
- 1948-53, "Standard (or "A type")" cylinder head, bare aluminium finish, 2 × SU H6 carburettors. The XK 120 C came with the C-type head (red) as an option from 1951 to 1952 with 2 × SU H8 carburettors. In 1953, the XK 120 C switched to a triple Weber 40 DCOE carburettor setup. The XK 120 SE and M came with the C-type head as an option with 2 × SU H6 carburettors (occasionally SU H8) - Jaguar XK140Jaguar XK140The Jaguar XK140 is a sports car manufactured by Jaguar between 1954 and 1957, the successor to Jaguar's highly successful XK120. Upgrades included better brakes, rack and pinion steering, increased suspension travel and modern tube type shock absorbers instead of the older lever arm...
- 1954-57, "Standard (or "A type")" cylinder head, 2 × SU H6 carburettors. The XK 140 SE or M came with the C-type head as an option, painted red with 2 × SU H6 or H8 carburettors - Jaguar XK 150 3.4Jaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1957-61, "B type" cylinder head, painted light blue-green, 2 × SU HD6 carburettors - Jaguar XK 150 3.4SJaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1957-61, "B type" cylinder head, painted orange, 3 × SU HD8 carburettors - Jaguar XK 150 3.8Jaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1958-61, "B type" cylinder head, painted dark blue metallic, 2 × SU HD6 carburettors - Jaguar XK150 3.8SJaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1958-61, "Straight port" cylinder head, painted pumpkin orange, 3 × SU HD8 carburettors - Jaguar Mark VIIJaguar Mark VIIThe Jaguar Mark VII was a large four-door sports sedan launched by Jaguar Cars of Coventry at the 1950 London Motor Show. It replaced the Jaguar Mark V, but as there was a Bentley Mark VI already on the market, Jaguar decided to call the next model Mark VII...
- 1950-54, ""A type" then "C type" (as option from April 1953) cylinder head, unpainted aluminium, 2 × SU H6 carburettors - Jaguar MkVIIMJaguar Mark VIIThe Jaguar Mark VII was a large four-door sports sedan launched by Jaguar Cars of Coventry at the 1950 London Motor Show. It replaced the Jaguar Mark V, but as there was a Bentley Mark VI already on the market, Jaguar decided to call the next model Mark VII...
- 1954-57, "C type" cylinder head, 2 × SU H6 carburettors, some had high-lift cams - Jaguar Mark VIIIJaguar Mark VIIIThe Jaguar Mark VIII is a large four-door sports sedan introduced by the Jaguar company of Coventry at the 1956 London Motor Show.-The body:The car shared its wheelbase with its predecessor, the Jaguar Mark VII, which outwardly it closely resembled. However, the interior fittings were more...
- 1956–1958, "B type" cylinder head, painted light blue-green, 2 × SU HD6 carburettors - Jaguar 3.4-litre 'Mark 1'Jaguar Mark 1The Jaguar Mark 1 was a saloon car produced by Jaguar between 1955 and 1959. Referred to in contemporary company documentation as the Jaguar 2.4-litre and Jaguar 3.4-litre, the word "Saloon" was often added. The designation "Mark 1" was included retrospectively upon its replacement by the Mark 2...
- 1957-59, "B type" cylinder head, painted light blue-green, 2 × SU HD6 carburettors - Jaguar 3.4-litre Mark 2Jaguar Mark 2The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
- 1959-67, "B type" cylinder head, painted light blue-green, 2 × SU HD6 carburettors - Jaguar 340 Mark 2Jaguar Mark 2The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
- 1967-68, "B type" cylinder head, ribbed cam covers, 2 × SU HD6 carburettors - Jaguar S-Type 3.4Jaguar S-Type (1963)The Jaguar S-Type was produced from 1963–68 as a technically more sophisticated development of the Jaguar Mark 2, offering buyers a more luxurious alternative to the Mark 2 without the size and expense of the Mark X. It sold alongside the Mark 2, as well as the Jaguar 420 following its release in...
- 1963-68, "B type" cylinder head painted light blue-green, ribbed cam covers, 2 × SU HD6 carburettors
2.4-litre
In the mid-1950s, Jaguar lacked a compact saloon of the type represented until 1949 by the Standard engined 1½ litre. In choosing a power unit for its all new compact saloon, Jaguar could choose between the 1,995 cc four cylinder XK prototype and a downsized version of the 3.4 litre six cylinder XK. The 4-cylinder was considered too low powered and unrefined. The 3.4 was already well “undersquare”, which means that its bore was much less than its stroke, so a smaller bore version of the 3.4 was not seen as a realistic proposition. Jaguar was therefore obliged to create a short stroke version of the 6-cylinder XK with a shorter cylinder block, reducing it in height from 11.5 in (292 mm) to 8.85 in (225 mm).Introduced in the Jaguar 2.4-litre in 1955, the engine had a stroke of 76.5 mm (3 in) while retaining the bore of 83 mm (3.3 in) to give a capacity of 2483 cc. Despite having a displacement of almost 2.5 litres, the new car was called the “Jaguar 2.4” to create an obvious separation from the old Standard 2½ litre and link it to the now familiar 3.4 litre XK engine. The first 2.4s produced 112 hp SAE gross using twin Solex downdraft carburettors.
In 1959 the engine was carried over into the new Mark 2, in which it produced 120 hp SAE gross, still with Solex carburettors. The Jaguar 240
Jaguar Mark 2
The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
was fitted with an uprated version of the engine, incorporating the straight-port cylinder head and twin SU carburettors delivering 133 bhp SAE gross.
The 2.4 litre XK6 was used in the following cars:
- Jaguar 2.4-litre 'Mark 1'Jaguar Mark 1The Jaguar Mark 1 was a saloon car produced by Jaguar between 1955 and 1959. Referred to in contemporary company documentation as the Jaguar 2.4-litre and Jaguar 3.4-litre, the word "Saloon" was often added. The designation "Mark 1" was included retrospectively upon its replacement by the Mark 2...
- 1955-59, "B type" cylinder head, unpainted, 2 × Solex B32PB15S carburettors, valve angles 30 degrees inlet, 45 degrees exhaust - Jaguar 2.4-litre Mark 2Jaguar Mark 2The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
- 1959-67, "B type" cylinder head, unpainted, 2 × Solex B32PB15S carburettors, valve angles 45 degrees inlet and exhaust - Jaguar 240 Mark 2Jaguar Mark 2The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
- 1967-69, "Straight port" cylinder head, unpainted, 2 × SU HD6 carburettors, valve angles 45 degrees inlet and exhaust
3.8-litre
The 3.8 litre version was released in 1958, initially for the last of the XK150s and the Mark IX saloon. It retained the 3.4’s bore centres and 106 mm (4.2 in) stroke but was bored out to 87 mm (3.4 in) for a total displacement of (3,781 cc / 230.7 cu-in). The distance between the cylinder bores was sufficiently small that it was decided to fit dry liners to the bores. The 3.8 had a number of detail differences from the 3.4, particularly in its valve gear and carburetion. The standard 3.8 produced 220 hp SAE gross and up to 265 hp SAE gross in the XK150SE with the straight port head.The 3.8 litre XK6 was used in the following road cars:
- Jaguar XK 150 3.8Jaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1958-61, "B type" cylinder head, painted dark blue metallic, 2 × SU HD6 carburettors - Jaguar XK150 3.8SJaguar XK150The Jaguar XK150 is a sports car produced by Jaguar between 1957 and 1961. It replaced the XK140.Initially it was available in Fixed Head Coupé and Drop Head Coupé versions. The Open Two Seater roadster was not launched until 1958...
- 1958-61, "Straight port" cylinder head, painted pumpkin orange, 3 × SU HD8 carburettors - Jaguar Mark IXJaguar Mark IXThe Jaguar Mark IX is a large luxury saloon car produced by Jaguar Cars between 1959 and 1961. It replaced the previous Mark VIII, and differed little in exterior appearance except for the new model name...
- 1958-61, "B type" cylinder head, painted dark blue metallic, 2 × SU HD6 carburettors - Jaguar Mark X 3.8Jaguar Mark XThe Jaguar Mark X was the top-of-the-range saloon car built by the British manufacturer Jaguar, originally aimed at the United States market. The Mark X succeeded the Mark IX as the company's large saloon model.-Body:...
- 1961-64, "Straight port" cylinder head, painted gold, 3 × SU HD8 carburettors - Jaguar Mark 2Jaguar Mark 2The Jaguar Mark 2 is a medium sized saloon car built from 1959 to 1967 by the Jaguar company in Coventry, England, as successors to the Jaguar 2.4 and 3.4 models, manufactured between 1957 and 1959...
- 1959-67, "B type" cylinder head, painted dark blue metallic, 2 × SU HD6 carburettors - Jaguar E-Type Series 1 3.8Jaguar E-typeThe Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
- 1961-64, "Straight port" cylinder head, painted orange then gold, 3 × SU HD8 carburettors - Jaguar S-Type 3.8Jaguar S-Type (1963)The Jaguar S-Type was produced from 1963–68 as a technically more sophisticated development of the Jaguar Mark 2, offering buyers a more luxurious alternative to the Mark 2 without the size and expense of the Mark X. It sold alongside the Mark 2, as well as the Jaguar 420 following its release in...
- 1963-68, "B type" cylinder head, dark blue metallic or later with ribbed cam covers and unpainted, 2 × SU HD6 carburettors - Panther J.72Panther J72The J.72 was the first product of the Panther Westwinds company, sold from 1972 through 1981. It was an ultra-exclusive luxury roadster, intended to compete with the best of the 1970s motor industry. It used mechanicals from the XJ12, including the 5.3 L Jaguar V12 engine, and was styled like...
3.0-litre
3-litre versions of the XK engine were built from 1959 onwards for FIA sports car racing. It was also popular with small race car manufacturers such as Lister Cars who could not afford to produce their own engines. As well as endurance racing, the engine was also used in Formula LibreFormula Libre
Formula Libre is a form of automobile racing allowing a wide variety of types, ages and makes of purpose-built racing cars to compete "head to head". This can make for some interesting matchups, and provides the opportunity for some compelling driving performances against superior machinery...
racing.
A 3.0 litre XK6 was used in the following road cars:
- Jaguar E2A prototype sports racer (1960)
- Jaguar E-typeJaguar E-typeThe Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
lightweight sports racer (1961) - Jaguar D-typeJaguar D-typeThe Jaguar D-Type, like its predecessor the C-Type, was a factory-built race car. Although it shared the basic straight-6 XK engine design with the C-Type, the majority of the car was radically different...
(non-works) sports racer (1959) - Lister Cars endurance and formula racers
- Hersham and Walton MotorsHersham and Walton MotorsHersham and Walton Motors is the world's longest established Aston Martin business and is well known as a racing car constructor. As a constructor, it is best known for its involvement in Formula Two from 1950 to 1953 and Formula One in 1954...
(HWM) endurance and formula racers - Cooper Car CompanyCooper Car CompanyThe Cooper Car Company was founded in 1946 by Charles Cooper and his son John Cooper. Together with John's boyhood friend, Eric Brandon, they began by building racing cars in Charles' small garage in Surbiton, Surrey, England in 1946...
endurance and formula racers - John TojeiroJohn TojeiroJohn Tojeiro , affectionately known as Toj, was an engineer and racing car designer, whose innovations helped to revolutionise car design in the 1950s and '60s....
endurance and formula racers
4.2-litre
The 4.2 litre version of the XK was officially released in 1964, although racers had been boring the 3.8 out all the way to 4.2 litres for years. The factory 4.2 litre block was a new Siamesed sleeve design which used respaced cylinders set evenly along the length of the block, new main bearing spacings and a new crankshaft. The middle two cylinders were moved closer together and the outer two moved further apart but the overall length of the block remained unchanged. This enabled the cylinder bores to be taken out to 92.07 mm (3.6 in) whilst retaining the familiar long stroke of 106 mm (4.2 in) for a total displacement of 4,235cc / 258.4cuin.Despite the re-spacing of the cylinder bores, the cylinder head castings remained unchanged. As a result, the centrelines of the combustion chambers in the head no longer aligned precisely with the centrelines of the cylinders but this did not matter greatly as the combustion chamber diameters in the head were smaller than the cylinder diameters. The 3.8 and 4.2 litre cylinder heads and cams are therefore interchangeable. The 4.2 litre engine from the factory had unsmoothed steps between the inlet manifold and head and the manifold gaskets were not a good match for the inlet ports. These engines therefore make excellent bases for some modification, achieving approx. 220 bhp SAE net and increased torque merely by "flowing" the head.
Published horsepower ratings of the various versions of the 4.2 litre are complicated by the switch from gross to net horsepower systems during its lifetime. For example, in 1965 the 4.2 litre with triple SU carburettors fitted to the US-specification E-Type was rated at 265 hp SAE gross whereas by 1969, now with twin Zenith-Stromberg carburettors, this had fallen to 246 hp SAE gross. The difference indicates the effect of the revised carburetion and other changes made to reduce exhaust emissions from US specification engines. Jeff Daniels' reference states that the similar twin Zenith-Stromberg version fitted to a US specification XJ6 was rated by Jaguar at 170 PS using the DIN net horsepower system, the difference being largely due to the effect of the gross versus net horsepower rating systems.
The 1987 Jaguar XJ6 was the last Jaguar
Jaguar (car)
Jaguar Cars Ltd, known simply as Jaguar , is a British luxury car manufacturer, headquartered in Whitley, Coventry, England. It is part of the Jaguar Land Rover business, a subsidiary of the Indian company Tata Motors....
car fitted with the XK6 engine. In 1992 the last Daimler
Daimler Motor Company
The Daimler Motor Company Limited was an independent British motor vehicle manufacturer founded in London by H J Lawson in 1896, which set up its manufacturing base in Coventry. The right to the use of the name Daimler had been purchased simultaneously from Gottlieb Daimler and Daimler Motoren...
DS420 Limousine was produced. Like all other DS420 limousines, it was equipped with a 4.2 litre XK6 engine. The 4.2 variant was also used in some military vehicles with relatively few modifications. The length of time the XK engine has remained in production means it has the rare accolade of having been in service in cars spanning six consecutive decades.
All of the 4.2-litre XK engines used the straight port head. After the arrival of the ribbed cam covers in 1967 the heads normally remained unpainted, which some sources describe as "silver".
The 4.2 litre XK6 was used in the following cars:
- Jaguar Mark X 4.2Jaguar Mark XThe Jaguar Mark X was the top-of-the-range saloon car built by the British manufacturer Jaguar, originally aimed at the United States market. The Mark X succeeded the Mark IX as the company's large saloon model.-Body:...
- 1964-66, “straight port” cylinder head, painted gold, 3 × SU HD8 carburettors - Jaguar 420 - 1966-68, 2 × SU HD8 carburettors
- Daimler SovereignDaimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
- 1966-69, 2 × SU HD8 carburettors - Jaguar 420GJaguar Mark XThe Jaguar Mark X was the top-of-the-range saloon car built by the British manufacturer Jaguar, originally aimed at the United States market. The Mark X succeeded the Mark IX as the company's large saloon model.-Body:...
- 1966-70, painted gold, 3 × SU HD8 carburettors - Jaguar E-Type Series 1 4.2Jaguar E-typeThe Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
- 1964-68, painted gold, 3 × SU HD8 carburettors (from 1967 US specification E-Types used 2 × Zenith-Stromberg 175 CDSE carburettor for reduced emissions) - Jaguar E-Type Series 2Jaguar E-typeThe Jaguar E-Type or XK-E is a British automobile, manufactured by Jaguar between 1961 and 1975. Its combination of good looks, high performance, and competitive pricing established the marque as an icon of 1960s motoring...
- 1968-70, 3 × SU HD8 carburettors (US specification E-Types used 2 × Zenith-Stromberg 175 CDSE carburettor for reduced emissions) - Jaguar XJ6 4.2 Series 1 - 1968-73, 2 × SU HD8 carburettors
- Daimler Sovereign 4.2 'XJ6' Series 1Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
- 1969-73, 2 × SU HD8 carburettors - Jaguar XJ6 4.2 Series 2 - 1973-74, 2 × SU HS8 carburettors
- Daimler Sovereign 4.2 'XJ6' Series 2Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
- 1973-74, 2 × SU HS8 carburettors - Jaguar XJ6 L 4.2 Series 2 - 1973-79, 2 × SU HS8 carburettors. From 1977, 2 × SU HIF7 carburettors, US market from May 1978 Bosch-Lucas L-Jetronic electronic injection
- Daimler Sovereign LWB 4.2 'XJ6' Series 2Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
- 1973-79 (and Daimler Vanden Plas 1975-79), 2 × SU HS8 carburettors. From 1977, 2 × SU HIIF7 carburettors, US market (VDP only) from May 1978 Bosch-Lucas L-Jetronic - Jaguar XJ6 4.2 Series 3 - 1979-87, 2 × SU carburettors or Bosch-Lucas L-Jetronic electronic injection
- Daimler 4.2 'XJ6' Series 3Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
- 1979-86, 2 × SU carburettors or Bosch-Lucas L-Jetronic electronic injection - Daimler DS420 LimousineDaimler DS420The Daimler DS420, popularly known as the Daimler Limousine, is a large limousine produced by Daimler Motor Company between 1968 and 1992. The vehicles are used extensively as official state cars in several countries, including by the British and Danish Royal Families...
- 1968-92, 2 × SU HD8 carburettors. From 1985 Bosch-Lucas L-Jetronic electronic injection - Panther J.72Panther J72The J.72 was the first product of the Panther Westwinds company, sold from 1972 through 1981. It was an ultra-exclusive luxury roadster, intended to compete with the best of the 1970s motor industry. It used mechanicals from the XJ12, including the 5.3 L Jaguar V12 engine, and was styled like...
- Panther De VillePanther De VilleThe Panther De Ville was a neo-classic luxury model from Panther Westwinds, the British specialty maker. Offered from 1974 to 1985, the De Ville was conceived by Robert Jankel to appeal to the taste of nouveau riche customers, including singer Elton John and actor Oliver Reed...
It was also used in the following military vehicles:
- FV101 ScorpionFV101 ScorpionThe FV101 Scorpion is a British armoured reconnaissance vehicle. It was the lead vehicle and the fire support type in the Combat Vehicle Reconnaissance , CVR, family of seven armoured vehicles...
, a British CVR(T) - FV107 ScimitarFV107 ScimitarFV107 Scimitar is an armoured reconnaissance vehicle used by the British Army. It is very similar to the FV101 Scorpion but mounts a high velocity 30 mm L21 RARDEN cannon instead of a 76 mm gun. It was issued to Royal Armoured Corps, Armoured Regiments in the Reconnaissance role...
, a British Armoured car.
2.8-litre
A 2.8 litre version of the XK was introduced for the entry-level XJ6 models in 1968. It returned to the old short block of the 2.4, retaining the bore of 83 mm (3.3 in) but lengthening the stroke by 9.5 mm (0.374015748031496 in) to 86 mm (3.4 in) to give a displacement of 2,792 cc / 170.4 cu-in. The power output of the 2.8 was listed as 142 PS DIN net, which cannot be directly compared with the 133 bhp SAE gross of the last of the 2.4s in the 240 Mark 2.The 2.8 gained a bad reputation early in its career due to a tendency for excessive carbon deposits to accumulate on the piston crowns during low-speed running, which would burn through the crowns when run at higher revs. This was later cured by a switch to stronger pistons but the engine was also a mediocre performer offering no real economy benefit and it was dropped in 1973, to be replaced by the ‘new’ 3.4.
All of the 2.8-litre XK engines used the straight port head unpainted, which some sources may describe as "silver", and had ribbed cam covers.
The 2.8 litre XK6 was used in the following cars:
- XJ6 2.8 Series 1 - 1968-73, 2 × SU HD8 carburettors
- Daimler Sovereign 2.8 'XJ6' Series 1Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
– 1969-72, 2 × SU HD8 carburettors - XJ6 2.8 Series 2 - 1973-74, 2 × SU HS8 carburettors
"New" 3.4-litre
Introduced in 1975 to replace the 2.8 as the entry level XJ6, the new 3.4 was not a simple revival of the original XK. Whilst it shared the old 3.4’s bore and stroke of 83 mm (3.3 in) and 106 mm (4.2 in) respectively, it was actually a small bore derivative of the 4.2, using its block, cylinder spacings, main bearing spacings and stiffer bottom end but dispensing with the cylinder liners used by the 3.8 and 4.2. It used a straight port head and delivered 161 PS DIN net and far superior torque to the 2.8.The "new 3.4" used the straight port head, had ribbed cam covers and the heads were unpainted.
The "New 3.4" litre XK6 was used in the following cars:
- XJ6 3.4 Series 2 - 1975-79, ribbed cam covers, 2 × SU HS8 carburettors. From 1977, 2 × SU HIIF7 carburettors
- Daimler Sovereign 'XJ6' 3.4 Series 2Daimler SovereignDaimler Sovereign was a name applied by British manufacturer Jaguar Cars to a sequence of luxury automobiles built by it but carrying the Daimler badge between 1966 and 1983....
– 1975-79, ribbed cam covers, 2 × SU HS8 carburettors. From 1977, 2 × SU HIIF7 carburettors - XJ6 Series 3 - 1979-86, ribbed cam covers, 2 × SU carburettors
Cylinder head types
The following table relates XK cylinder head type to Jaguar/Daimler model and includes the paint colours applied to certain versions of the cylinder head in the 1950s and 60s. Unpainted heads are sometimes referred to as “silver” but this is merely the natural colour of the aluminium alloy.| “A” head | Mark VII Mark VII M XK 120 XK 120 SE XK 120 M XK 140 XK 140 SE XK 140 M |
| “B” head | Mark VIII (painted light blue-green) Mark IX (painted dark blue metallic) XK 150 3.4 (painted light blue-green) XK 150 3.4 S (painted orange) XK 150 3.8 (painted dark blue metallic) Prototype E1A Prototype E2A “wide angle” 2.4-litre 'Mark 1' 3.4-litre 'Mark 1' (painted light blue-green) 2.4-litre 'Mark 2' 3.4-litre 'Mark 2' (painted light blue-green) 3.8-litre 'Mark 2' (painted dark blue metallic) 340 'Mark 2' S-Type 3.4 (painted light blue-green) S-Type 3.8 (painted dark blue metallic) |
| “C” head | Mark VII (as option from April 1953) Mark VII M (as option) XK 120 C XK 120 SE (as option from April 1954) XK 120 M (as option from April 1954) XK 140 SE (as option) (painted red) XK 140 M (as option) (painted red) |
| “Straight port” head | XK 150 3.8 S (painted orange) D-Type (“wide angle” from 1955) 240 Mark II 420 Daimler Sovereign (420) E-Type 'Series 1'(painted orange then later gold) E-Type Lightweight E-Type 4.2 (painted gold) E-Type Series 2 Mark X (painted gold) 420G Daimler DS 420 XJ6 2.8 and 4.2 Series 1 Daimler Sovereign 2.8 and 4.2 (Series 1) XJ6 2.8 and 4.2 Series 2 Daimler Sovereign (Series 2) XJ6 Coupe Daimler Sovereign Two-Door XJ 3.4 Series 2 Daimler Sovereign 3.4 (Series 2) XJ6 L Series 2 Daimler VDP Series 2 XJ6 Series 3 Daimler Series 3 |