Jaguar XK6 engine - Revision history

Red marquis at 15:25, 18 December 2009

2009-12-18T15:25:09Z

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	\|Manufacturer = [[Jaguar]]		\|Manufacturer = [[Jaguar]]
	\|aka = '''Type aka here, not up there'''		\|aka = '''Type aka here, not up there'''
	\|Type = ''~~'Note what type of fuel it consumes'~~''		\|Type = ''Petrol''
	\|Production/Introduction = 1949–1992		\|Production/Introduction = 1949–1992
	\|Status = ''Discontinued''		\|Status = ''Discontinued''
	\|Displacement = '''in litres, cc's or cu-in.'''		\|Displacement = '''in litres, cc's or cu-in.'''
	\|Aspiration = '''write its type of aspiration'''		\|Aspiration = '''write its type of aspiration'''
	\|Configuration = ~~'''write the configuration of the cylinders'''~~		\|Configuration = Inline
	\|Cylinders = ~~'''write the number of cylinders present'''~~		\|Cylinders = 6
	\|Fuel System = '''write if it is injected or carburated and the system used'''		\|Fuel System = '''write if it is injected or carburated and the system used'''
	\|Lubrification = '''indicate the engine's type of lubrification'''		\|Lubrification = '''indicate the engine's type of lubrification'''

Red marquis: /* "New 3.4" */

2009-12-18T15:24:07Z

"New 3.4"

← Older revision		Revision as of 15:24, 18 December 2009
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	=="New 3.4"==		=="New 3.4"==
	Introduced in 1973 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 ~~{{convert\|~~83\|mm\|in~~\|1\|abbr=on}}~~ and ~~{{convert\|~~106\|mm\|in~~\|1\|abbr=on}}~~ 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 ~~{{convert\|~~161\|PS\|kW hp~~\|0\|abbr=on}}~~ and far superior torque to the 2.8.		Introduced in 1973 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 (118 kW; 159 hp) and far superior torque to the 2.8.

	The "New 3.4" litre XK6 was used in the following cars:		The "New 3.4" litre XK6 was used in the following cars:

Red marquis: /* 2.8 */

2009-12-18T15:23:49Z

2.8

← Older revision		Revision as of 15:23, 18 December 2009
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	==2.8==		==2.8==

	A 2.8 litre version 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 ~~{{convert\|~~83\|mm\|in~~\|1\|abbr=on}}~~ but lengthening the stroke by ~~{{convert\|~~9.5\|mm\|in~~\|1\|abbr=on}}~~ to ~~{{convert\|~~86\|mm\|in~~\|1\|abbr=on}}~~ to give a displacement of 2,792cc / 170.4cuin. The power output of the 2.8 was listed as ~~{{convert\|~~142\|PS\|kW hp~~\|0\|abbr=on}}~~, which cannot be directly compared with the 133bhp (gross) of the last of the 2.4s in the 240 Mark II.		A 2.8 litre version 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 (0.4 in) to 86 mm (3.4 in) to give a displacement of 2,792cc / 170.4cuin. The power output of the 2.8 was listed as 142 PS (104 kW; 140 hp), which cannot be directly compared with the 133bhp (gross) of the last of the 2.4s in the 240 Mark II.

	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.		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.

Red marquis: /* 4.2 */

2009-12-18T15:23:16Z

4.2

← Older revision		Revision as of 15:23, 18 December 2009
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	==4.2==		==4.2==
	The 4.2 litre version was officially released in 1965, 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 an all 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 ~~{{convert\|~~92.07\|mm\|in~~\|1\|abbr=on}}~~ whilst retaining the familiar long stroke of ~~{{convert\|~~106\|mm\|in~~\|1\|abbr=on}}~~ for a total displacement of 4,235cc / 258.4cuin.		The 4.2 litre version was officially released in 1965, 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 an all 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 cylinder heads and cams are therefore interchangeable. The 4.2 litre engine was poorly finished from the factory with the heads not being flowed and the gaskets too small for the gap. These engines therefore make excellent bases for some modifications achieving approx. ~~{{convert\|~~220\|bhp\|kW PS~~\|0\|abbr=on}}~~ and much more torque just by flowing the head.		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 cylinder heads and cams are therefore interchangeable. The 4.2 litre engine was poorly finished from the factory with the heads not being flowed and the gaskets too small for the gap. These engines therefore make excellent bases for some modifications achieving approx. 220 bhp (164 kW; 223 PS) and much more torque just by flowing the head.

	The version of the engine fitted with [[Zenith Carburetters\|Zenith-Stromberg]] carburettors produced ~~{{convert\|~~170\|PS\|kW hp~~\|0\|abbr=on}}~~, whereas the triple [[SU carburettor\|SU]] HD8 carburettor version was rated at ~~{{Convert\|~~265\|hp\|kW~~\|0\|abbr=on}}~~ [[Horsepower#SAE_gross_horsepower\|gross]] (the difference in the measurement systems being significant).		The version of the engine fitted with [[Zenith Carburetters\|Zenith-Stromberg]] carburettors produced 170 PS (125 kW; 168 hp), whereas the triple [[SU carburettor\|SU]] HD8 carburettor version was rated at 265 hp (198 kW) [[Horsepower#SAE_gross_horsepower\|gross]] (the difference in the measurement systems being significant).

	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 produced high torque thanks to its more advanced valve and head configuration.		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 produced high torque thanks to its more advanced valve and head configuration.

	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 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 6 consecutive decades.		The 1987 [[Jaguar XJ6]] was the last [[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 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 6 consecutive decades.

	The 4.2 litre XK6 was used in the following cars:		The 4.2 litre XK6 was used in the following cars:
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	It was also used in the following military vehicles:		It was also used in the following military vehicles:
	* [[FV101 Scorpion]], a British CVR(T)		* FV101 Scorpion, a British CVR(T)
	* [[FV107 Scimitar]], a British Armoured car.		* FV107 Scimitar, a British Armoured car.

	==2.8==		==2.8==

Red marquis: /* 3.8 */

2009-12-18T15:21:11Z

3.8

← Older revision		Revision as of 15:21, 18 December 2009
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	==3.8==		==3.8==

	The 3.8 L 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 ~~{{convert\|~~106\|mm\|in~~\|1\|abbr=on}}~~ stroke but was bored out to ~~{{convert\|~~87\|mm\|in~~\|1\|abbr=on}}~~ for a total displacement of (3,781 cc / 230.7 cuin). The distance between the cylinder bores was sufficiently small that it was decided to fit dry liners to the cylinder 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 ~~{{Convert\|~~220\|hp\|kW~~\|0\|abbr=on}}~~ gross and up to ~~{{Convert\|~~265\|hp\|kW~~\|0\|abbr=on}}~~ gross in the XK150SE with the straight port head.		The 3.8 L 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 cuin). The distance between the cylinder bores was sufficiently small that it was decided to fit dry liners to the cylinder 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 (164 kW) gross and up to 265 hp (198 kW) gross in the XK150SE with the straight port head.

	The 3.8 litre XK6 was used in the following cars:		The 3.8 litre XK6 was used in the following cars:

Red marquis: /* 2.4 */

2009-12-18T15:20:35Z

2.4

← Older revision		Revision as of 15:20, 18 December 2009
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	==2.4==		==2.4==

	In the mid-1950s, Jaguar lacked a compact saloon of the type represented until 1949 by the Standard engine 1-1/2 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 ~~{{convert\|~~11.5\|in\|mm~~\|0\|abbr=on}}~~ to ~~{{convert\|~~8.85\|in\|mm~~\|0\|abbr=on}}~~.		In the mid-1950s, Jaguar lacked a compact saloon of the type represented until 1949 by the Standard engine 1-1/2 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 in 1955, the engine had a stroke of ~~{{convert\|~~76.5\|mm\|in~~\|1\|abbr=on}}~~ while retaining the bore of ~~{{convert\|~~83\|mm\|in~~\|1\|abbr=on}}~~ to give a capacity of ~~{{convert\|2483\|~~cc~~\|abbr=on}}~~. 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 2-1/2 litre and link it to the now familiar 3.4 litre XK engine. The first 2.4s produced ~~{{Convert\|~~112\|hp\|kW~~\|0\|abbr=on}}~~ [[Horsepower#SAE_gross_horsepower\|gross]] using twin Solex downdraft carburettors.		Introduced in the Jaguar 2.4 in 1955, the engine had a stroke of 76.5 mm (3.0 in) while retaining the bore of 83 mm (3.3 in) to give a capacity of 2,483 cc (151.5 cu in). 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 2-1/2 litre and link it to the now familiar 3.4 litre XK engine. The first 2.4s produced 112 hp (84 kW) [[Horsepower#SAE_gross_horsepower\|gross]] using twin Solex downdraft carburettors.
	In 1959 the engine was carried over into the new Mark II, in which it produced ~~{{Convert\|~~120\|hp\|kW~~\|0\|abbr=on}}~~ [[Horsepower#SAE_gross_horsepower\|gross]], still with Solex carburettors. The [[Jaguar Mark 2\|Jaguar 240]] was fitted with an uprated version of the engine, incorporating the straight-port cylinder head and twin SU carburettors.
			In 1959 the engine was carried over into the new Mark II, in which it produced 120 hp (89 kW) [[Horsepower#SAE_gross_horsepower\|gross]], still with Solex carburettors. The [[Jaguar Mark 2\|Jaguar 240]] was fitted with an uprated version of the engine, incorporating the straight-port cylinder head and twin SU carburettors.

	The 2.4 litre XK6 was used in the following cars:		The 2.4 litre XK6 was used in the following cars:

Red marquis: /* 3.4 */

2009-12-18T15:13:49Z

3.4

← Older revision		Revision as of 15:13, 18 December 2009
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	==3.4==		==3.4==

	The first production use of the XK 6-cylinder was in the 1949 [[Jaguar XK120]], which used the 3.4 L (3,442 cc / 210 cuin) version with an ~~{{convert\|~~83\|mm\|in~~\|1\|abbr=on}}~~ bore and ~~{{convert\|~~106\|mm\|in~~\|1\|abbr=on}}~~ 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 ~~{{convert\|~~160\|bhp\|kW~~\|0\|abbr=on}}~~ [[Horsepower#SAE_gross_horsepower\|gross]] at a compression ratio of 8:1, rising ~~to {{convert\|210\|~~bhp\|kW~~\|0\|abbr=on}}~~ gross with the C-type cylinder head (confusingly not the head from the C-Type as raced at Le Mans) all the way to ~~{{convert\|~~250\|bhp\|kW~~\|0\|abbr=on}}~~ [[Horsepower#SAE_gross_horsepower\|gross]] with the “straight port” head at a compression ratio of 9:1 as fitted to the XK150SE.		The first production use of the XK 6-cylinder was in the 1949 [[Jaguar XK120]], which used the 3.4 L (3,442 cc / 210 cuin) 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 (119 kW) [[Horsepower#SAE_gross_horsepower\|gross]] at a compression ratio of 8:1, rising to210 bhp (157 kW) gross with the C-type cylinder head (confusingly not the head from the C-Type as raced at Le Mans) all the way to 250 bhp (186 kW) [[Horsepower#SAE_gross_horsepower\|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 (described below) was released, there was pressure on Jaguar to fit the 3.4 litre engine to it. This was duly done in 1957, the car being known as the Jaguar 3.4. The designation “Mark I” for these cars was applied retrospectively, after the release of the Mark II in 1958.		Almost as soon as the new compact Jaguar 2.4 (described below) was released, there was pressure on Jaguar to fit the 3.4 litre engine to it. This was duly done in 1957, the car being known as the Jaguar 3.4. The designation “Mark I” for these cars was applied retrospectively, after the release of the Mark II in 1958.

Red marquis: /* Description */

2009-12-18T15:10:17Z

Description

← Older revision		Revision as of 15:10, 18 December 2009
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	The first engines to receive fuel injection were some D-Type sports racing cars but fuel injection did not become standard on the road cars until the late 1970s.		The first engines to receive fuel injection were some D-Type sports racing cars but fuel injection did not become standard on the road cars until the late 1970s.

	Readers should note that during the 1950s and 60s Jaguar used the [[Horsepower#SAE_gross_horsepower\|SAE gross horsepower]] measurement system used by US manufacturers, as otherwise Jaguar cars would have appeared under-powered in comparison with US cars. Gross power was flattering as 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 [[Horsepower#SAE_net_horsepower\|SAE net horsepower]] system around 1972, although Jaguar power ratings of that era may also be expressed using the [[DIN]] rating system. An objective comparison of the power outputs of the various models of XK6 powered Jaguar is therefore quite problematic.		Readers should note that during the 1950s and 60s Jaguar used the [[Horsepower#SAE_gross_horsepower\|SAE gross horsepower]] measurement system used by US manufacturers, as otherwise Jaguar cars would have appeared under-powered in comparison with US cars. Gross power was flattering as 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 [[Horsepower#SAE_net_horsepower\|SAE net horsepower]] system around 1972, although Jaguar power ratings of that era may also be expressed using the DIN rating system. An objective comparison of the power outputs of the various models of XK6 powered Jaguar is therefore quite problematic.

	==3.4==		==3.4==

Red marquis: /* Description */

2009-12-18T15:09:45Z

Description

← Older revision		Revision as of 15:09, 18 December 2009
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	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. Three 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 cam chain tensioner proved to be too weak and after a couple of years was changed to hydraulic operation.		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. Three 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 cam chain tensioner proved to be too weak and after a couple of years was changed to hydraulic operation.

	The cylinder heads were made of 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 ~~{{convert\|~~70\|lb~~\|abbr=on}}~~ compared with a similar head made of cast iron. Special attention was paid to the gas flow, with ~~[[Weslake\|~~Harry Weslake]] 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, camshaft lift, compression ratio and carburetion were frequently amended from model to model, depending upon whether power or torque were being emphasised. A straight port head was introduced later for use with the SU carburettors.		The cylinder heads were made of 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 (32 kg) compared with a similar head made of cast iron. Special attention was paid to the gas flow, with Harry Weslake 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, camshaft lift, compression ratio and carburetion were frequently amended from model to model, depending upon whether power or torque were being emphasised. A straight port head was introduced later for use with the SU carburettors.

	The block was made of cast iron (with the exception of some made of alloy for racing engines), with the crankcase split on the centreline of the seven-bearing crankshaft. The crankshaft was made of EN.16 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 ensure there would be no damaging crankshaft resonances. The design and materials of the bottom of the engine hardly changed throughout its life, apart from the respaced cylinders required by 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.		The block was made of cast iron (with the exception of some made of alloy for racing engines), with the crankcase split on the centreline of the seven-bearing crankshaft. The crankshaft was made of EN.16 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 ensure there would be no damaging crankshaft resonances. The design and materials of the bottom of the engine hardly changed throughout its life, apart from the respaced cylinders required by 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.

Red marquis: /* Development */

2009-12-18T15:07:34Z

Development

← Older revision		Revision as of 15:07, 18 December 2009
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	By September 1947 a 3.2 litre 6-cylinder version had been produced, called the "XJ 6-cylinder", which was intended to replace both of the 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]], followed by the [[Jaguar Mark VII]] and a number of other Jaguar models in subsequent years.		By September 1947 a 3.2 litre 6-cylinder version had been produced, called the "XJ 6-cylinder", which was intended to replace both of the 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]], followed by the [[Jaguar Mark VII]] and a number of other Jaguar models in subsequent years.

	The XG prototype soldiered on as a component testbed until 1948. Confusingly, 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 to the [[IMechE]] in February 1953<ref>Heynes, W M. ''The Jaguar Engine'', a paper presented to the Institution of Mechanical Engineers on 27 February 1953</ref> , 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.		The XG prototype soldiered on as a component testbed until 1948. Confusingly, 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 to the IMechE in February 1953<ref>Heynes, W M. ''The Jaguar Engine'', a paper presented to the Institution of Mechanical Engineers on 27 February 1953</ref> , 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 I) released in that year. None of the 4-cylinder prototypes ever advanced to production.		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 I) released in that year. None of the 4-cylinder prototypes ever advanced to production.