Concepts and prototypes : Jaguar XJ21

Thoughts on replacing the E-type weren’t limited to the V12-powered XJ-S grand tourer. Jaguar was also cooking up this potentially pretty sports car to supplement the new and exciting XJ6 saloon.

But, as Ian Nicholls explains, things weren’t always that simple…

The missing link

The final XJ21 proposal - this would have sold alongside the XJ-S, giving the company a pair of two-seaters in its range...

The final XJ21 proposal – this would have sold alongside the XJ-S, giving the company a pair of two-seaters in its range…

THE Jaguar XJ21 was the missing link between the E-type sports car and XJ-S grand tourer. When the XJ-S was unveilled in 1975, many pundits were disapointed it wasn’t the out and out sports car they’d been hoping for. But, in truth, the XJ-S was not a direct E-Type replacement at all, and was never intended as such. It appears that an XJ-S type GT was always part of Jaguar’s wider plans to manufacture an upmarket luxury grand tourer which would retail at a higher price than the E-type and earn more profit for the Coventry company.

Yet at the same time, Jaguar also thought it could develop a direct E-type replacement, which became project XJ21, and even worked on a smaller sports car (Project XJ17) using the Daimler 2.5-litre V8 and Jaguar 3.5-litre V8, then under development. Jaguar was also drawing up plans for a Mk2 saloon replacement, ambitious indeed for a company that produced on average 24,000 cars per year. The harsh reality of Jaguar’s true financial position was that its profits were insufficient to pay for all of this.

On 11 July 1966, it was announced that Sir William Lyons’ Jaguar Group, which also comprised commercial vehicle operations, would be merging with the British Motor Corporation to form British Motor Holdings. In reality, this was a takeover by BMC of Jaguar, but Sir William Lyons maintained control of his empire. Lyons agreed to the ‘merger’ in order to safeguard his body supply, which came from BMC-owned Pressed Steel Fisher; to secure the future of the company (as his only son had died in 1955); and to get financial backing for future model programmes.

The priority was to get the XJ4 saloon car project onto the market place, and the modular 60-degree V8/V12 that was intended to power future Jaguars, into production also. The XJ4 became the XJ6 , and confusingly the V8/V12 engine was codenamed XJ6. Jaguar had been working on a V12 engine on and off since the 1950s, but the genesis of the eventual production V12 began with the abortive XJ13 racing car designed for a Le Mans comeback. The racing V12, with a capacity of 4994cc, was codenamed XJ1. By 1965, Jaguar was using a MkX saloon as a testbed. On 30 October 1965, chief test driver Norman Dewis recorded the performance of XJ5 no5, a MK10 saloon testbed fitted with a carburettor 5 litre quad cam V12.

‘….speed recorded through the timing lights was 134mph with tachometer reading 6000 rpm. At the end of the straight 6500 rpm was observed which is equal to 145mph… during a second run the car had just passed the timing lights when the engine produced a seizure, disengaging top gear and switching off saved the engine from more serious damage… low speed flexibility is very good, it being possible to drive the car at 6mph in top gear on full throttle.’

Engine options

Later, the V12-engined MkX test cars were reclassified as XJ10s. When the XJ13 racing programme was axed, Jaguar engineers decided to increase the V12’s capacity to 5343cc in order to attain greater volumetric efficiency. At the time, Jaguar had two V12 designs battling for the honour of being put into production: The quad-cam design was the brainchild of William Heynes and Claude Bailly. It was up against a simpler twin cam design concieved by Walter Hassan and Harry Mundy. The quad cam unit had the advantage of greater top end power, but that seemed to be the only area where it was superior to the twin-cam engine. The Hassan/Mundy engine was simpler, more compact and easier to install in the bodyshells of Jaguar’s forthcoming models. And it had more low end torque and superior acceleration to the quad cam unit – in the end this was the V12 configuration that went into production.

During the development of the V12, Walter Hassan and Harry Mundy were asked to produce a V8 version of the new engine, obviously to maximise Jaguar’s investment. According to Jeff Daniels, ‘this engine consisted quite literally of the middle two-thirds of the V12, with two cylinders lopped off either end. The result, inevitably, was a V8 with the ‘ wrong’ included angle between banks of 60 degrees rather than 90 degrees, but also an engine which could potentially be machined on a common line with the V12 and which, with a swept volume of 3563cc might replace the XK with a lighter, higher revving and altogether more modern power unit suitable for a new sportscar or a range of smaller saloons.’

By late 1965, Jaguar was testing 60 degree V8s. That year, a 3.3-litre V8 with Lucas fuel injection produced 235bhp at 6500rpm, (as much as the later 3980cc AJ6 engine of 1990).

On 4 October 1966, the two technical directors of Jaguar and BMC, William Heynes and Alec Issigonis met at Longbridge to discuss future projects. Among the matters on the agenda was the possibility of inserting the Jaguar XK engine in the BMC ADO30 sports car project. Also that month work appears to have begun on the XJ21 project, which was intended as an E-Type replacement with more internal room.

Hello to the XJ21

The first XJ21 proposal of October 1966, drawn by Jaguar aerodynamicist Malcom Sayer was called Body Type A, and appears to have been an evoloution of the 2+2 E-type launched in March that year. The track was increased, although body width remained the same. The steering wheel and front seats were moved forward. Externally the Body Type A XJ21 had a revised air intake, a more raked screen and exposed headlamps. Some of these features would appear on the Series 2 E-type announced in October 1968. It appears that during the long drawn out process to replace the E-type, Malcolm Sayer appears to have had a free hand to design what he wanted, whereas the styling of the saloons remained the preserve of company boss Sir William Lyons.

In December 1966, Malcolm Sayer was drawing ADO30 projects with a 3-litre XK engine and the 2.5- and 4.5-litre Daimler V8s inherited when Jaguar bought the Radford car maker in 1960. However ADO30 would bite the dust in the spring of 1967. The New Year brought more work on the XJ21, when in January 1967 Malcolm Sayer drew Body Type B. Sayer explained in a note on his drawing.

‘Main particulars same as Body Type A, but different nose and intake, rear wing widened, rear bumper and underpan lowered.’

Also that month Sayer drew a roadster version of the XJ21, again using the 2+2 wheelbase but with a wider track. This idea would not be wasted as the Series 3 E-type roadster would use the 2+2 chassis. March 1967 brought further revisions to the XJ21, which was still very much E-type based. Later Sayer at an undetermined date drew a two-seat roadster and fixed head coupé using the 96 inch wheelbase of the equivalent E-Type, again retaining a wider track. While all this was going on Jaguar were still pressing on with V8 and V12 development.

Work on a V8 variant was not proceeding smoothly. In 1967, a 3560cc unit with twin SU carburettors produced 204bhp at 5750rpm, which on paper compares well with the later Rover SD1 Vitesse. However, producing acceptable torque figures was proving problematic.

Jaguar’s styling team’s exciting future models line-up…

Around 1967/68 Jaguar’s styling department produced a document listing current and future models complete with basic illustrations of the cars and some cursory details. In the future models section was the forthcoming XJ4 saloon fitted with 2.6 and 3 litre XK engines, a 3.5 litre V8, 4.2 litre XK and 5.3 V12 engine. There were two E-Type/XJ21 style models, a 2 seater roadster and a 2+2 coupé. Also there was a two-seater coupé which seemed to have XJ-S-style flying buttresses, though probably it was still XJ21 based. These three future models all used the 3.5-litre V8 and 5.3-litre V12. It appears that having begun the V8 as an afterthought, Jaguar had every confidence that their engineers could make the 60-degree unit into a workable, integral part of the companies future model programme.

Finally there was listed a four-seater sports saloon which used the Daimler 2.5-litre V8 and the 3.5-litre Jaguar V8. Three drawings exist of this small GT, all of which used the 96-inch wheelbase of the two-seater E-type, but used a 2+2 seating arrangement. Known simply as the XJ 3-litre GT, this ‘mini’-Jaguar used a twin headlamp arrangement similar to that used on the later XJ-S. Another feature of this car was the truncated nose and tail which made it look like a Mini Marcos. This could have been the XJ17 project.

Jaguar’s Leyland adventure

The XJ4 GT was an early effort at creating a sporty car based on the XJ saloon floorpan.

In May 1968 British Leyland officially came into being, and all future model programmes were now up for discussion. Jaguar was now bedfellows with Rover, who had a 3.5-litre V8 that actually worked and in production. It is often claimed that Sir William Lyons, who was BLMC’s deputy chairman, was responsible for the axing of the mid engined Rover P6 BS, because it was a potential rival for the E-type. Certainly that thesis is feasible, but it must also be remembered that the 4.2-litre E-type was larger engined than the 3.5-litre P6BS, and the 5.3-litre Series 3 was on the horizon. Also BLMC had other medium size engined sporting cars nearer production such as the 2.5-litre Triumph TR6, the 3-litre MGC and the 3-litre Triumph Stag. Why did BLMC need another similar product? It is possible that both the Rover P6 BS and 3-litre Jaguar GT never made it to production because they were surplus to requirements?

By 1968, in response to newer sporting cars from the likes of Lamborghini and Ferrari, the XJ21 began to take on more Italianate styling and departed from E-type style curves. Malcolm Sayer was also being aided by Oliver Winterbottom, who would go on to a distinguished career with TVR and Lotus. Winterbottom had some quarter-scale clay models made of his version of the XJ21. During 1968 Malcom Sayer seems to have settled on a final XJ21 style. Internal Jaguar documents detailed the forthcoming timetable of events for the replacement of the original E-type.

  • October 1968 was when the Series 2 E-type was scheduled to appear.
  • June 1969 would see the introduction of the V12 E-type.
  • September 1970 was when the restyled XJ21 would supercede the E-type.
More Italianate XJ21 proposal...

More Italianate XJ21 proposal…

In the event the only target met was the introduction in October 1968 of the Series 2 E-Type. Delays in the development of the V12 engine pushed back the timetable and other factors intervened. On September 9th 1968 Malcolm Sayer wrote to Sir William Lyons with a completely new concept, a ‘2+2 sports based on XJ4 parts’. Remember that XJ4 was the factory codename for the XJ6 saloon, now less than three weeks away from its public unveilling.

Malcolm Sayer continued: ‘The image sought after is of a low wide high speed car at least as eyecatching as those the Italians will produce will produce, even if it means sacrificing some of the more sensible values such as luggage and passenger space, silence, ease of entry.’

This seems to mark the genesis of the the XJ27/XJ-S project, however it had not received official backing yet. On November 14th 1968, Technical Director William Heynes wrote to Sir William Lyons. Heynes had pushed for the forthcoming V12 engine to make its mass production debut in the E-type, a project known as XJ25.

‘Engineering is well in hand on the body for the XJ25 and will, in any case, have to be completed and prototypes made, and this is the only possible way in which we can test the 12 cylinder engine in the E-Type chassis. The chassis is virtually identical whether we use the XJ25 or XJ21. If we decide, as I believe it is necessary, to go ahead with the XJ25, this will set back the XJ21 programme another six to eight months but this is immaterial… I am convinced it is essential for the 12-cylinder engine to be introduced in the E-type before it is introduced in the XJ6 and the only possible way of doing this is to press forward with the XJ25. This model could then be introduced to the market in January 1970, which would suit us very well, in as much as we could introduce the 12 cylinder engine on the XJ6 car at the Motor Show of the same year.’

Later on Heynes turned to the subject of the XJ21.

‘On the XJ21, this is an entirely new car and we want to have a look at the following items to bring them up to current practices:

  • 1.Air conditioning
  • 2.Automatic windows
  • 3.New power brake system
  • 4.Power clutch operation
  • 5.Disappearing headlamps
  • 6.Disc locks

‘…It must be emphasized that for the achievement of these dates on either model it is essential that the three XJ25 prototypes already put in hand are completed immediately. It is agreed that the first car can be running by the end of February (1969) and the other two cars will follow in not more than a four week interval. Failure in this respect will make the achievement of the dates impossible.’

As it turned out the XJ25 did not go on sale in January 1970, but late March 1971 as the Series 3 E-type. Developing the V12 was taking longer than expected which Jaguar blamed on British Leyland. While Heynes was writing away the press were getting their hands on the new XJ6 saloon and raving about its combination of superlative ride, refinement and handling, which seemed to make the E-type look like something from another era. Sometime in 1969 the XJ21 concept finally died a natural death and the XJ27 emerged as the replacement for the E-type. It appears Jaguar got as far as discussing tooling for the XJ21 with Pressed Steel Fisher. But were any XJ21 running prototypes actually built? Not only was the concept of using the XJ saloon platform as the basis of the E-Type replacement a cost saving option, it was also a more modern chassis.

Work was still proceeding on the V8 version of the V12 engine and by 1971 it looked as if the unit was about to get the green light. By February 1971, Harry Mundy had tested an XJ4 chassis fitted with a V8 and a double bulkhead which gave a, ‘noticeble improvement in noise suppression, but there is still some resonance confined to the floor panels, especially at 2700-3200rpm with wide open throttle. Above this speed there are no further critical periods and in the higher range he (Mundy) considers the unit to be noticeably smoother than either the 4.2 or the 2.8 (XK).’

While all this was going on the XJ25 Series 3 E-type and its V12 engine was finally announced on 25 March 1971.

By August 1971, the V8 had been fitted with twin balancer shafts, which were driven at twice the engine speed by toothed belts, and seemed on the verge of being developed into production reality. By that November, the V8 was axed as the following quote from a Model Progress Meeting states: ‘Following the final assessment of the V8 engine it has been decided to stop further development work… the engine in its present state is thought to be just acceptable, but it is not considered to be an economical production proposition.’

Oliver Winterbottom's proposal for the XJ21...

Oliver Winterbottom’s proposal for the XJ21…

Whether this was really true is open to question. Perhaps Jaguar, who had a waiting list for the XJ6 saloon, felt that the forthcoming XJ12 variant would take up most of their production. Certainly producing a V8 and V12 on the same production tools would be more economical than producing two seperate engine designs, and a replacement for the 1948 vintage XK engine would still have to be found.

Walter Hassan, in his autobiography Climax in Coventry, stated, ‘The V8… was a disappointment to us all. Engineers know that V8s should have 90 degrees between the banks, but we had hoped that the unpleasant secondary vibrations involved in a 60-degree design could be suppressed by clever engine mounting. But this proved not to be possible and, as with the four-cylinder XK engines of the 1940s, there were unpleasant vibrations in the structure, felt also through the gear lever, which we could not tame.’

George Buck, then a Jaguar engine development engineer later recalled: ‘One could consider a V8 version of the same V12 engine by just chopping off four cylinders from the back and it could be produced on the same transfer machinery. It would produce 3.5 litres of engine which was very handy for an alternative lower capacity engine. In fact we made quite a few pukka V8 versions of which we fitted to an early XJ6. I thought it was a good concept. It was a very satisfying engine and was obviously very competitive because it was giving 200bhp. It was a very able unit in the saloon and obviously gave you more space under the bonnet. What killed it was the fact that being a 60 degree vee, following on from the 12, you were in a situation where you’d got two four cylinder engines in effect and because they were not at 90 degrees, you finished up having to cater for secondary out-of balance forces. Ultimately we were able to eliminate those completely by fitting separate balance shafts on but that was an added complication.’

It has always been claimed that it was the addition of separate balance shafts that made the V8 an unviable production proposition and incapable of using the V12 production lines. George Buck disagreed: ‘We could, but it was unacceptable to Bob Knight. He felt he did not want to cater for this secondary out-of balance problem. We could get rid of it by suitable insulation and at one stage, I think we’d just about cured it but it was dropped, which is a shame. It started off initially, the V8, by adapting one of the twin cam V12 engines and simply altering the crankshaft. At this stage it was still in a V12 carcass.’

XJ21 in its final - open - form...

XJ21 in its final – open – form…

...and as a coupé.

…and as a coupé.

Bob Knight who became Jaguar Technical Director in 1972 gave his views on the V8 engine: ‘It had quite a good power output on two carburettors, but it sounded and felt like a medium sized four. It was the uneven firing which was the worst feature. What one heard was two cylinders firing quite close together and then there was a longer interval before the next two were heard relatively close together, and so on. In spite of the twice engine speed balancers, which were tried to cure the secondary balance problem, it still sounded like a four.’

In July 1972 the XJ12 saloon was announced, the car that in shortened wheelbase form would provide the basis for the forthcoming XJ27/XJ-S. Journalist and E-Type owner Denis Jenkinson borrowed one and later commented: ‘This was in the autumn of 1972 and it proved to be a giant of a car, with road holding and handling up to using the full potential of the V12 engine. I soon realized that the E-type era was over, for on a cross country run you would have been hard pressed to keep that big saloon in sight with an E-type.’

The XJ21 with its E-Type origins would have paled in comparison with the XJ27/XJ-S on the road. Also in 1972 Jaguar made another attempt to utilise the V12 tooling to produce a smaller capacity engine. This was a slant-six, effectively a V12 sliced lengthways – and with a longer stroke to increase capacity. Run in XJ test beds, these engines needed the capacity increase in order to beef-up performance, and made them different enough to need all-new production tooling – as a result it, like the V8 beforehand, was cancelled.

George Buck recalled this engine: ‘Obviously it was thought that, since the V12 was successful, then half a V12, which would give you about 2.65 litres, would be a useful thing to have. Again you could make the thing on the same production line, use the same components, pistons, rods, and all you would need to change was the crank and block. So the first slant six was a sawn off V12 and we made several of those. They even ran in XJ’s in that form. It was quite a reasonable performing vehicle and quite economical so we did a lot of work on the testbed to arrive at the best combination of manifolding, air filtration, exhaust system and so on.’

Trevor Crisp, who succeeded Harry Mundy as Group Chief Engineer (Power Units) recalled these engines. ‘These engine were considered to be insufficiently powerful. We were quite limited on the engine capacity and just halving the 5.3 didn’t really give us a big enough capacity in any case.’

Bob Knight later commented on Jaguar’s attempt to maximise its investment in a new engine production line; ‘It is a good example of the futility of making such sophisticated and totally dedicated equipment for a relatively small volume manufacturer. The people who were dealing with this at Jaguar undoubtedly, at the time, did not realise the importance of providing for future flexibility. Flexibility in tooling is the name of the game.’

The V8/V12 programme had cost Jaguar some £3m in production tooling, about £34m in 2009 terms, and for a brief period it seemed as if Jaguar had got away with its failure to replace the XK engine. Acclaim for the XJ12 was overwhelming and Jaguar couldn’t make enough of them. The XJ12 had superceded the XJ6 as the best car in the world and it looked as if Jaguar simply had to produce as many premium priced V12 engined cars as it could and it would be laughing all the way to the bank.

But as events would show, after the October 1973 energy crisis, the V12 engine, the only tangible result of all the financial and development effort expended proved something of an expensive white elephant. Critically acclaimed but only fitted to a minority of Jaguar cars, due to its high fuel consumption. Although Jaguar revealed the cost of tooling for the V12 as £3m, the actual cost of developing the engine was not made known.

The XJ27 finally went on sale in September 1975 as the XJ-S to mixed reviews. Technically it was a superb car, but some traditionalists disliked its unconventional styling, which took time to be accepted. This was an era when British Leyland launched a whole range of unconventional looking cars such as the Austin Allegro, 18-22/Princess, Triumph TR7 and now the Jaguar XJ-S. Jaguar still needed to replace the ageing XK engine, and although the XJ-S was selling in sufficient quantities, its 5.3 litre take it or leave it V12 engine option was deterring customers in a world still coming to terms with the October 1973 energy crisis. Another negative aspect of the Jaguar V12 engine was that American buyers, thanks to Federal anti-emisssions legislation, did not get the full fat European performance, 244bhp instead of 285bhp.

After the XJ21…

24-valve version of the XK engine was on the cards for a while...

24-valve version of the XK engine was on the cards for a while…

The V12 configuration was more vulnerable to ‘green’ laws aimed at restricting harmful emissions than other types of engines. Jaguar had known since 1967 about pending US anti-emission laws, yet still went ahead and brought the V12 engine to production. Jaguar then looked at updating the existing XK engine. In 1976 Jaguar built three 3.8-litre XKs with a lighter engine block mated to a 24-valve twin-cam cylinder head. Performance was satisfactory, but the engine was not light enough. Also, the cost estimates for the 24-valve XK engine were nearly as much as those needed for a completely new design – and in the end that was the deciding factor. It also hit the cutting-room floor.

In 1976 work began on the AJ6, a six-cylinder engine of all-aluminium construction. Harry Mundy led the design team and the first prototype ran in early 1979. The main recipient for the engine was to be the XJ40 saloon, so there were two initial variants, a 24-valve 3.6-litre and a 2.9-litre 12-valve budget engine. Jaguar also tested a 3.8-litre version, but for the time being felt the 3.6-litre produced all the performance and economy needed for the task. XJ-S test beds had been used to evaluate the AJ6, and the decision was made to debut the new engine in the XJ-S. By 1979/80 the world was experiencing a second energy crisis, which combined with BL build quality and reliability issues came close to killing the XJ-S.

When the AJ6 3.6-litre engine appeared in the XJ-S from 1983 there was a noticeble improvement in sales as the cars sales appeal was widened. This was when the XJ-S matured into a trusted brand in its own right, its unique styling setting it apart from its rivals. And Jaguar needed the car to keep on selling as its intended replacement, the XJ41/42 failed to make the grade and was cancelled by March 1990. The best year for the XJ-S was 1989, a time when the XJ40 saloon was stalling in the marketplace as reliability and quality issues came to the fore. The AJ6 engine was further improved into the AJ16 in 1994. The six cylinder engine was less prone to missions legislation than the V12, and for American buyers, the performance gap between the two variants was minimal and demand for the V12 gradually dried up. Jaguar now owned by Ford then facelifted the now ageing XJ-S to prolong its life, which reached the market place in 1993. Ford then backed a new replacement project for the XJ-S, codenamed X100 which was to use the under development AJ26 V8 engine.

Two of the options considered involved the XJ-S. One was to prolong the life of the distinctive XJ-S by dropping in the new V8 engine. Another more extreme option was to install the V8 with a further £99m. facelift. Sketches and mock ups were prepared, but it was felt that there was to much of the old XJ-S coming through. In the end Ford and Jaguar opted for an all new style, but retained the XJ-S floorpan. This was launched as the XK8 in 1996.

Keith Adams

About the Author:

Created in 2001 and watched it steadily grow into AROnline. Is the Editor of Classic Car Weekly, and has contributed to various motoring titles including Octane, Evo, Honest John, CAR magazine, Autocar, Diesel Car, Practical Performance Car, Performance French Car, Car Mechanics, Jaguar World Monthly, Classic Car Weekly, MG Enthusiast, Modern MINI, Practical Classics, Fifth Gear Website, and the the Motoring Independent... Likes 'conditionally challenged' motors and taking them on unfeasable adventures all across Europe.

6 Comments on "Concepts and prototypes : Jaguar XJ21"

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  1. Will M says:

    Bit glad the XJS facelift didn’t occur. The oval-shape (Ford influence?) headlights and grille are more mk6 Escort than straight-edged XJS.
    By the 90s it was a bit long in the tooth, the XK was a worthy replacement for the time.

  2. Mick says:

    The Oliver Winterbottom proposal has a lot of Fiat Dino Coupe in it, a very Italian looking car actually.

    and I do agree with the above writer, the last XJ-S facelift does really not look that great. Good they didn’t ruin the design in the end…

  3. Paul Jenner says:

    I like the restyled XJS shown above. With some further design tweeks I would have preferred this styling route more than the XK we eventually got. I always thought the XK to be a bit bland. The newer XK is even worse, at least to my eye.

  4. Nate says:

    Is there any connection between the 4-seater XJ4 GT / XJ 3-litre GT sports saloon and the stillborn Jaguar XJ “Junior” rival to the Triumph 2000/Rover P6 that was to use Coventry Climax CFA/CFF 1800-2500 V8 engines and MG MGC-derived running gear?

  5. MM says:

    The first XJ12 saloon I saw on the road,in Doncaster Yorks, soon after the model went on general sal, the car had the personal registration plate of 12XJ. From memory it was a saloon and the paint finish was a sort of salmon-pink.

    With such a distinctive registration plate, was this a factory demonstrator or a private owner?

    I wonder if the car still exists?

    • MM says:

      Correction: from memory the salmon pink car was not badged as a Jaguar XJ12, I am recalling that it wasbadged as a Daimler Double-Six

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