Saving Grace – Part Six

Today we interrogate Jaguar’s quality claims, explore Browns Lane’s engine policy – and indulge in a spot of counter-factuality.

(c) Auto-Didakt

Unreliable and unjustifiable, its cars had become a laughing stock, its management a comedy and its accounts a tragedy. Only when it began to take itself very seriously indeed, to cultivate the quality it had previously scorned did things change…” (LJK Setright – Car 1986)

It has been retrospectively stated that the Egan-led quality drive was more illusory than real, which is perhaps a little unfair to the huge effort from all concerned. There was however, in Egan parlance, perhaps a little more sizzle than steak to it. Nevertheless, the reforms had a basis in fact and if the JD Power statistics were any guide, it’s evident that Jaguar made significant strides in this area.

In 1983, BMW’s Eberhard von Kuenheim toured the Browns Lane facility. What he made of it is undocumented, but he must have been, to say the least, given to a measure of incredulity. Nevertheless by then, Jaguar had largely got to grips with building Series III to an acceptable standard. However, that standard remained discernibly lower than that of its Munich rival and at the time, potential suitor.

The XJ bodyshell, while now more accurately put together, remained a patchwork requiring a high degree of hand-finishing, its interior an alluring combination of tastefully matched, finely crafted natural materials and cheap-feeling injection mouldings, while its final assembly remained locked in the past.

A major upswing in durability terms occurred once Jaguar embarked upon a full-time on-site proving regime, building a dedicated base in Phoenix, Arizona. Regular forays to the Nardo test-track in Southern Italy and to the Middle East, Australia and Canada led to significant improvements for the customer.

But what hadn’t changed was the fact that the cars remained sensitive to neglect or careless ownership and were not as robust as they needed to be, especially once they reached their second or third owners. But Series III (and the XJ-S) were late-’60s designs with inbuilt design limitations and there was probably a limit to what could be achieved without significant and highly expensive alterations.

Ironically, the model which formed the bulk of global Series III sales was perhaps the most mechanically fragile. The 4.2 litre version of the long-lived XK in-line six had been something of a botch-job by Jaguar standards. Necessitating an element of jiggery-pokery in order to gain the additional bore widths, the engine became fundamentally compromised from a thermal standpoint.

4.2 XK (left) and 5.3 V12 (c) Jaguar Cars

Reviewing the technicalities of Jaguar’s revived mid-range engine in 1979, Car magazine’s LJK Setright noted the much-needed alterations had resulted in a torque curve of remarkable linearity, with maximum torque being developed at a mere 1500 rpm, which meant the driver never really needed to explore the upper reaches of the rev range, where the 4.2 tended to lose its composure and get decidedly hot under the collar.

Despite its physical size and vast weight, (as heavy as the larger V12), the 4.2 gained a reputation as a fragile engine and was never much regarded within Browns Lane. It’s certainly no accident that the factory never raced it.

Yet it outsold the more complex but superior V12 unit by a huge margin, despite offering broadly similar fuel economy. Yes the twelve cost more – to buy, to service and most likely in depreciation (always a Jaguar bugbear), but it offered something utterly unique – an uncanny smoothness and silence of operation, which as Jim Randle observed to this author, was as close to the characteristics of an electric motor as an internal combustion engine could reasonably be contrived.

But if the V12 cost more, the 4.2 was in turn worth far less. The irony of course being that while the V12 was designed expressly with the US market in mind, it was not sold there (in the XJ saloon at least) from 1983-onwards.

Viewed with hindsight, Jaguar made a fundamental error in prioritising the twelve over a smaller capacity unit. The contemporary thinking was that a V8 could be built on the same architecture, but for a variety of reasons it wasn’t possible (at the time at least) to create a unit which met Jaguar standards of smoothness.

(c) Car Magazine

Unfortunately, what doesn’t appear to have been explored was a similarly derived V6 unit. While an experimental 2.7 litre slant six was created off the V12 block, a 60° V6 of broadly similar capacity would have offered a more compact package, the inherent mechanical balance implicit with a 60° inclined angle, and the ability to build it on the same underutilised and expensive transfer line as the twelve.

The primary drawback would of course have been a lack of swept volume, but as an entry level unit, it could have offered many advantages and with the benefit of forced induction, could have given Jaguar the outputs they required. Certainly, a Series III with a lightweight, more fuel efficient (and sweet-running) engine not only seems a highly alluring prospect, but something of a missed opportunity. Furthermore, such a power unit could have proven highly advantageous to BL, being precisely the capacity required for the upper reaches of the Rover SD1 range, for example, rather than the larger than ideal Buick-derived 3.5 litre V8.

By the late ’70s, the necessity for a large-capacity diesel powerplant became apparent within BL. Upon Spen King’s suggestion, a diesel unit based on the block of the existing Rover V8 was developed in conjunction with Perkins. Primarily intended for Land Rover, but also for SD1, there were suggestions at the time that Jaguar could also be a recipient of what became known as the Iceberg programme. However, it fell victim to BL’s cash crisis.

A powertrain project which came a good deal closer to fruition was XJ59 – a Jaguar programme which saw the adoption of a VM Motori turbodiesel which was fitted to a number of SIII development cars around 1981/82. This unit, an in-line six of 3.6 litres, developed 150 bhp at 4200 rpm and 288 lbs ft of torque at 2400 rpm.

Those outputs were broadly similar to the US-spec 4.2 but gave notably better fuel economy. America had briefly embraced diesel following the 1979 oil embargo and Mercedes had introduced diesel versions of both W123 and W126 models, which had proven popular. In 1981, a BL spokesman told Car magazine they planned to introduce it into the US market for the 1983 model year.

However as fuel consumption concerns abated, the diesel XJ, despite having been largely proven was shelved; Jim Randle telling Motor’s Jeremy Sinek in 1983, “should the market require it in future, we could introduce it quite rapidly”. Another missed opportunity perhaps, since such an engine might have opened Jaguar to more of the European market.

Randle expanded a little more on this matter when we spoke in 2016. “We looked at diesel engines in the early ‘80s, using VM. It was built like an Aston Martin engine, where you have a tunnel through the crankcase, and each of the main bearings sits in a circular cup, as it were. It was interesting, turbocharged, but not a performer. It had the potential for finding some extra customers, but in the end, I think, sales and marketing weren’t keen”.

When I put it to him that perhaps a diesel didn’t really fit with Jaguar’s NVH ethos at the time, he replied; “No, it was difficult – mostly airborne [noise] though. We put extra sealing on the bulkheads, and things like that. But no, it didn’t immediately cause you to want to buy one”.

Upon reflection, it does appear that perhaps instead of viewing Browns Lane as a thorny irritant to be subdued, BL might have been better served by having employed Jaguar as the primary power-unit technology-centre for the group. Certainly their V12 engine had the potential to be sliced and diced in a number of ways which could potentially have been highly beneficial to the business as a whole and to Jaguar as a profit centre within the organisation. Another case of the BL charter?

Saving Grace continues here

©Driven to write. All rights reserved.

Author: Eóin Doyle

Co-Founder. Editor. Content Provider.

30 thoughts on “Saving Grace – Part Six”

  1. Jaguar’s diesel projects were rather confusing ranging from the 3.6 VM Motori turbodiesel (likely the same used in the AMC Eagle), Project Iceberg’s dieselization of the Rover V8 (giving Jaguar the jitters) and apparently the Jaguar AJ6 engine (which was said to be built with dieselization in mind).

    The first two were putting out around 150 hp (though some claim the Project Iceberg turbodiesel was only good for 125 hp not 150 hp), which would have potentially served as benchmarks for a theoretical AJ6 turbodiesel.

    If Mercedes-Benz managed to build both 60-degree V6s and 90-degree V8s on the same production line, surely Jaguar was capable of performing a similar feat with a 90-degree V8 being built alongside 60-degree V6s/V12s (instead of the abortive 60-degree V8) with the former sharing much of the latter’s architecture?

    Speaking of the Jaguar V12 aside from forming the basis of smaller V8 and V6 engines, in retrospect what else could have been done to improve it beyond the unrealised DOHC versions that were said to not have been an improvement over the existing V12?

    1. NVH problems of a sixty degree V8 could have been solved by the same measures taken to tame a ninety degree V6: stepped crankpins. These would even have allowed the choice between an ‘American’ uneven 540/180 firing order or an ‘Italian’ 360/360 firing order. The eternal problem of all sixty degree engines would have remained, lack of space between cylinder banks.

      I remember seeing Jaguars (can’t memorize whether they were SII or SIII) with Steyr experimental diesel engines. Six cylinder inline, cast iron cylinders with tunnel type crankshaft carriers (very unusual, like the VM engines) in one piece and a separate, vertically split aluminium crankcase with integral sump totally separate from the cylinder unit with a two fingers wide rubber seal running between the two units around the engine just below the cylinder head. The engines were direct injection pump jet types without turbo with very rough running characteristics but impressive torque.

    2. “If Mercedes-Benz managed to build both 60-degree V6s and 90-degree V8s on the same production line,”

      The Mercedes V6s introduced in the late 90s were ninety degrees so they could be built on the V8 production line. Their current V6s are 60 degrees. I’m not sure if they are built on the same line or not.

      A modern engine machining factory has more flexibility, but back in the day, the transfer machines they were using had a fixed angle for the cylinder banks that could not be altered. The cylinder honing equipment, drills, milling machines, cutters, broaches… etc.. were all at a fixed angle.

    3. Dave

      Is it known what the displacement of the experimental Steyr diesel engines were and whether they were used in marine or military applications?

      Angel Martin

      So engine machining factories of the period did not have the same flexibility as today? Seem to recall an article or few saying the M276 60-degree and M278 90-degree V8 engines were built on the same production line along with sharing a number of features with each other.

    4. @Bob. M112 V6 and M272 V6 were 90 degrees and V8 based. Not sure about the later engines.

      The old transfer line factories had less flexibility because the machinery was fixed and set up for a single engine.

      It’s hard to find good video of current factory block machining but the newer engine machining plants use more generic CNC machines fed by robots. Here is some from the BMW factory in China.

    5. The diesel engined Jaguars I mentioned were Steyr’s project, not Jaguar’s. Steyr chose the XJ because they wanted to show off their new engine concept in a car known for its smooth running engines.
      *IIRC* the engine had a bit over three litres and around 150 or 160 hp and was one of the first applications of pump jet direct injection in car engines long before Fiat brought the first direct injection Croma. The weird two piece block design was chosen for its noise suppression characteristics.

    6. Dave

      Thanks for the information.

      The only references on Steyr’s inline-6 diesels online (or at least their modern day versions) seem to displace around 3.2-litres. Given the direct-injected Croma diesel appeared in 1986, would it be accurate to say Steyr’s project was around the mid-1970s to early-1980s?

    7. I don’t remember the precise year, but it must have been around 1980. I just happened to visit Jaguar Salzburg where there was (no relation to my visit there) a press information day on these Steyr-engined Jaguars. The journalists invariably compared the diesel to the V12 and commented accordingly, which was a bit unfair because the engine actually was astonishingly cultivated, particularly taking into account it was an early pump jet design without much electronics.

    8. Dave: Comparing just about any contemporary internal combustion engine with Mundy and Hassan’s V12 was more than a little unfair, least of all a diesel unit. The timelines are interesting however, given that at the time, Stan Paskin was overseeing the VM Motori installation into the XJ at Browns Lane. But then, the motor industry is a contained and somewhat incestuous micro-universe, so it’s perhaps possible the chaps at Steyr got wind of this and made something of a counter-pitch.

    9. Uncovered a bit more on the Steyr experimental diesel project used in a Jaguar XJ assuming the following detailed below is regarding the same engine project, seems the project’s roots also partly stem from BMW yet it is not clear if the project drew upon BMW’s existing M20 or M30 petrol engines as a starting point and no details such as displacement are available* (BMW: The History of Engines by Dr Karlheinz Lange).

      During the period from 1978 to 1982 BMW worked on a new diesel engine concept in cooperation with the Steyr-Daimler-Puch AG in Steyr, Austria. Intended to be built in both four and six cylinder versions, the engine had a range of technically interesting design features. Particularly noteworthy was its direct injection system using individual pump-jet elements which were operated by the overhead camshaft.

      In order to avoid problems caused by the high cylinder pressure typical of a diesel, the cylinder head designed as a unitized Monobloc with the cylinders, as had been used in BMW’s early aircraft engines. To optimize the engine’s acoustic properties – noise being another diesel disadvantage – its load-bearing crankcase was surrounded by a rubber-mounting housing.

      In the sum of all its technical sub-concepts this engine proved to be very complicated, preventing its volume production from being realized in the short term. As a result BMW dropped this concept and continued solely with the development of its M105 (aka M21) diesel engine. All BMW’s diesel engine activities, including development and manufacture, were concentrated in its newly-built history at Steyr. This plant later took over the majority of petrol engine production as well.

  2. Bob: From my understanding, Harry Mundy (who became Jaguar’s Director of powertrain Engineering as well as co-architect of the V12) schemed AJ6 with one eye at Mercedes’ well-regarded contemporary diesel engines, telling journalist Ronald Barker in 1988 that his rationale was that should they require a diesel AJ6 variant, it would be more straightforward to duplicate ground already broken at Sindelfingen. However, to the best of my knowledge, no DERV AJ6 was built. However, it is said to have dictated AJ6’s basic architecture to the degree that it was a physically larger block than it might otherwise have been. However, when I put it to Jim Randle as to whether AJ6 had been conceived as a modular unit (four/five cylinder), as some journalists (step forward Mr. Cropley) suggested, he made it clear that no such plans existed.

    Just for the sake of clarity, the abortive V8 was a 60 degree unit, derived from the V12’s inclined angle. It was abandoned owing to seemingly intractable NVH issues. However, I spoke to an engineer who spent his formative years working with Ralph Smith in Whitley at Jaguar’s Advanced Engineering skunkworks during the late 1980s, who told me he solved the rough-running issue with this unit. This might perhaps suggest that the issues as outlined could have been a matter of dogma as much as anything. However, given that both Bob Knight and Harry Mundy are no longer with us, I am reluctant to endorse this view. You will find more on the subject of this power unit in our interview with Jim Randle in the archive.

    The V12 deserves an article in itself (which will happen in the fullness of time), as its creation (like most Jaguar projects) was somewhat convoluted, so I will refrain from commenting further on that matter for the present.

    1. So Harry Mundy was looking to the 5-cylinder Mercedes-Benz OM617 diesel as inspiration for a potential dieselized AJ6 engine?

      Thought it was the 6-cylinder Mercedes-Benz OM603 however the latter appeared about 2 years after the AJ6 engine.

      Have read about Jaguar’s abortive 60-degree V8 engine project, though find it difficult to believe Jaguar seriously considered it instead of looking at a 90-degree V8.

      Jaguar did after all look at 1.8-2.5 Coventry Climax CFF/CFA V8 for their Junior XJ project (not sure whether there was room for further enlargement) and already had the Daimler V8, which despite its apparent limitations deserved a better fate. Have heard of murmurs about Jaguar looking at other V8 projects during the 1950s-1960s though nothing viable as a production car engine.

  3. I always thought that the opportunity missed by Jaguar on engines was the late 1970’s redesign of the XK6 with a new, lighter block and 4 valve per cylinder aluminum head.

    The idea was a lighter cast iron block based on a new casting with slightly reduced capacity and bore size for better cooling and a 4 valve head for ~240 hp (also 4 valves gives approx 10 percent better fuel consumption).

    The block could have been machined and built on existing machinery. And used the BL experience (positive and negative) from the Dolomite Sprint engine.

    Ironically, that would have been a low cost, low risk, high return engine program of the type which has always been shunned by Jaguar. Their pattern is to swing for the fences with high cost, high risk powertrain designs. (eg V12, AJ8, all electric)

    1. The experimental alloy XK unit was a 3.8 litre, which was pretty much the optimum swept volume for that power unit. Nobody had much time for the 4.2 But either way, owing to its antiquity, it remained an enormous lump of thing.

      The issue of the XK redesign was addressed by Jim Randle in a 1983 interview in Motor magazine. In this he outlined that the primary drawback with the XK unit was not only its age in conceptual terms, but the age of its tooling. He pointed out that the costs involved in producing it with an alloy block (which had been envisaged) and Harry Mundy’s 24 valve cylinder head was such that they might as well design a new engine from scratch, avoiding legacy issues which the XK unit was saddled with and obtaining the benefits of a lighter, more adaptable engine.

      One of these aspects in AJ6’s favour was, that there was considerable scope to, as Mr. Randle put it, ‘tighten economies if necessary’ – one of the potential developments being something akin to what BMW were doing at the time with their ETA series of engines – the thinking of which he described as being in his view quite sound.

      Unfortunately, I’m separated from my archive at present, so am unable to furnish direct quotes, so this thumbnail sketch (so to speak) will have to suffice for the present time.

    2. “He pointed out that the costs involved in producing it with an alloy block (which had been envisaged) and Harry Mundy’s 24 valve cylinder head was such that they might as well design a new engine from scratch,”

      This is my point about Jaguar. Always the high risk design. In this case a completely new block with a change to aluminum and a completely new rotating assembly, as well as a new head. As well as a completely new assembly line, new castings, entirely new machines, new production process.

      Much more potential for problems. Many more potential points of failure. Especially risky for a company like Jaguar with prior reputation for iffy quality, reliability and durability.

      Compare to: an updated XK engine where they use an evolution of the existing engine rotating assembly, a new thin wall casting of the existing block in cast iron (so none of the risks of aluminum blocks) and a new cylinder head. Replace the worn machines on an assembly line that already exists, that works and is reliable ,and that the employees now how to build.

      It seems to me that a small company like Jaguar would want to be risk averse when the upside isn’t that big and the downside is really huge.

    3. I acknowledge your point Angel but what I will say is that AJ6 proved to be a very robust engine in service, in addition to being quite an efficient one. It was probably the closest Jaguar came to producing a bulletproof engine and certainly proved the least of XJ40’s issues, which were it seems mostly electronic in nature. Additionally, I’m not certain that a revised XK as you envisage would have given them a smaller capacity unit. Although it was rather underpowered, the 2.9 AJ6 opened Jaguar to a market the larger capacity unit would never have unlocked – especially where the latter would have been prohibitively taxed.

    4. From reading about the proposed 2.6-3.0-litre all-alloy short-stroke XK6 engines that was envisioned to put out 185 hp (Net) in 3-litre form, was under the impression based on the 2.6-litre versions enlargement to the (albeit largely unrelated / notorious) 2.6-litre would have meant a theoretical enlargement from a 3-litre to a 3.2-litre potentially putting out around 197 hp (Net)?

      Additionally how to the proposed 2.6-3.0-litre all-alloy short-stroke XK6 engines differ from the experimental 3.8-litre alloy XK6 unit or were both projects linked?

    5. Yes, the AJ6/AJ16 was probably Jaguar’s most robust engine (certainly at launch). But they got lucky. Compare to the AJ8.

      My point is the risks of doing too much new stuff all at once. Look at the XJ40. There were so many new components and manufacturing processes on that car – no wonder they had launch problems !

      If the XJ40 was launched with only the new body, the new paint shop, new abs and new rear suspension they would have been much better off.

      As it was they also had a new engine control, new high pressure hydraulics, new digital dash, new climate control, all new electrical system, new self levelling rear suspension…. It they had deferred or skipped all of that and used updates of existing components they would have had a much better launch. Those things could have been added incrementally to mid-cycle updates.

      Ironically, a lot of that stuff had disappeared by late XJ40 production anyway !

      On the smaller AJ6, all AJ6s used a 91mm bore and different stroke lengths, so an updated block casting XK presumably could have done the same.

    6. Meant to say “the (albeit largely unrelated / notorious) 2.8-litre version”

    7. Angel: You are not alone in taking that view – in fact, another former Jaguar insider I spoke to held broadly similar opinions. On one hand I can accept the contention, and when I put it to Mr Randle that perhaps a less technically dense car might have been a more expedient proposition, he was quite insistent that all of the ‘innovations’ within XJ40 were a direct response to the known and much-criticised problems with the earlier cars and were conceived to ensure durability. In addition, XJ40 was created in this manner in order to jump a 20-year technological gap, owing to the stagnation which occurred under BL. Whether Jaguar was in a position to build such a car is a good question. I think we can safely say from a distance of years that they were not.

      On the other hand I maintain that there is something rather laudable in the attempt to reach for excellence when something less would probably have sufficed. Where would we be without this approach? Probably where we are now, I might suggest. So yes, perhaps Jim Randle and Jaguar took an over-ambitious path, but as someone who appreciates elegant engineering, I’m rather glad they did – in the same way as I applaud the adoption of a V12 when yet another V8 in a world drowning in the things would have been enough.

      It isn’t as though the outcomes would have been vastly different anyway. If XJ40 had been technically a warmed over Series III, it would still have been viewed entirely within its predecessor’s shadow, Ford would still have taken over in ’89, as they would not have been denied. The cars that followed would still have been watered down and the styling retro-focused. If anything, the ’40 would probably have been even more derided in retrospect – at least those who understand it can appreciate the fact that it was a rather intelligent piece of engineering, if lacking the impossible grace of Series III – a body design which has never been surpassed, by Jaguar or anyone else.

      I’m not expecting to convince anyone on this – I have to admit to a wholly irrational (and unapologetic) bias towards XJ40 and its creators.

      Bob: I don’t know if the 3.0 litre alloy block XK envisioned for the XJ4 programme was related to the 3.8 litre 24-valve unit developed during the early ’70s. Very little is documented about either engine and sadly, most of the people who were directly involved are no longer above ground. Part of the reason for this of course is that most of them came to nothing owing to a chronic lack of funds. BL was obsessively focussed on the volume car division and everyone else could essentially go whistle.

    8. “On the other hand I maintain that there is something rather laudable in the attempt to reach for excellence when something less would probably have sufficed. ”

      Eoin. I guess it is just a difference in philosophy. Bad launch quality is never excellence in my view. Toyota limits the number of new features and new production processes in any model launch because they know how dangerous too much new stuff is to quality.

      I’m actually a fan of the XJ40, even the styling. But I much prefer the later cars when the failure prone crap had been removed.

  4. Actually, Eóin, with your insights into the workings of Jaguar, and the toxic BL political environment within which it operated, you’ve gone a long way towards convincing me that there was really something heroic about the XJ40, even if its execution was tragically flawed. It’s easy for companies like Toyota that replace models with metronomic regularity to pursue a cautious and incremental approach to the introduction of new technologies but, as you point out, Jaguar was trying to make up for almost two decades of elegant stagnation. Also, one shouldn’t forget that the XJ40 was good enough to be evolved into the X300 and X308, giving it an impressive lifespan of 17 years. Without the xJ40, it’s doubtful that there would have been anything that Ford would have considered worth buying*, so Jaguar might no longer exist.

    * No, the irony of that statement is not lost on me!

    1. I guess I am not making my point clear. At launch the XJ40 had a new:
      -body structure
      -paint process
      -anti-lock brakes
      -rear suspension
      -revised engine electronic control
      -high pressure hydraulics
      -electrical wiring system
      -new climate control
      -digital electronic dash
      -self-levelling rear suspension

      What would it have hurt if the launch had been limited to:
      -body structure
      -paint process
      -anti-lock brakes
      -rear suspension

      and the rest introduced at a mid-cycle refresh in 1990 when they had more opportunity to test them?
      -revised engine electronic control
      -high pressure hydraulics
      -electrical wiring system
      -new climate control
      -digital electronic dash
      -self-levelling rear suspension

      After two decades, what is another 3 years to get it right?

      Jaguar spent the 1980’s trying to rebuild their shattered quality reputation, then they destroyed it again with the XJ40. And the main culprits were items like the digital dash and self levelling suspension which they deleted in later models anyway. Brilliant !

      If I was more charitable I would not point out that Jaguar wasted budget and engineering resources on nonsense like a digital dash when they KNEW that the USA had a supplemental restraint mandate coming into force. And, instead of having airbags in place when competitors did, the XJ40 had to make do with mouse belts.

  5. Re XK engine
    Jaguar were in a serious situation. The XK engine needed, at minimum, a total top to bottom refresh. It needed a new cylinder block with altered cylinder bore pitch and a new deck height and it needed to be cast in a new material. It needed an entirely new cylinder head with four valves per cylinder. It needed an entirely new piston and rod assembly. It needed new manifolding. It needed revised sealing systems (e.g. rear main seal in particular but also attention to the sealing of the front timing chest). It needed updated engine management etc. etc. etc. and on it goes (this is analogous to grandad’s old axe). Now that be just the start of the problems.

    Even if Jaguar were have redone all these design details and gone forth to build some new generation XK prototype engines and then proceeded even further to test, develop and prove that they achieve what was wanted (in terms of performance, economy, emissions, aesthetics, packaging and, the most vexatious of all, refinement- NVH and all that), then they’d still have needed to erect a production facility to manufacture the new generation XK engine in sufficient volume efficiently and economically.

    The problem for Jaguar was that the existing XK engine line was already very old and well out of date by the late ’70s. The tooling was flogged out and becoming more unreliable. Certain of the process was outmoded, needing far too many man-hours to run. It all needed much fettling and fiddling and intensive maintenance than rationally justifiable. Issues were getting more difficult to deal with, as the XK line and its tooling continued to deteriorate (under normal wear and tear). Tolerances were, even by the standards of the ’70s, casual (being diplomatic here). All this meant that major investment in the line was becoming more and more urgent.

    Jaguar had a choice to make.
    1. They could refit the line to continue erecting an old fashioned engine.
    2. They could refit the line to erect a revised version of an old fashioned engine.
    3. They could build an up to date new production line to erect an old fashioned engine.
    4. They could build an up to date new production line to erect a revised version of an old fashioned engine.
    5. They could build an up to date new production line to erect an up to date new engine which did not suffer from the design limitations of the old fashioned engine.

    History demonstrates that they selected option #5. At the time it made engineering and economic sense to have done this. It still does in hindsight.

    Some on this site prefer option #2 or #4. The trouble with these was either cost near as much if not more than option #5. For Jaguar option #2 or #4 meant they would have still been stuck with a basic engine design with in-built limitations dating from late ’40s ICE practice (when the XK series engine finally departed production, it had been in continuous manufacture for longer than any other passenger car engine ever- it was OLD and so was the tooling used to manufacture it- actually some of it was even older than the engine design itself). Romantically it would have been nice to have continued on with XK, but from the point of view of real world engineering and economics it was anything but a serious option for Jaguar to do that.

    As to risk. Every time a new model or a new engine is introduced it comes with risk for the manufacturer. What many critics fail to understand is that a revised or new production line/process/tooling etc. also comes with risk. For Jaguar, sticking with the XK was no lesser risk than going over to the AJ6.

    Re V-6 engine
    No. These are not balanced. There are residual imbalances of a type which are absent in conventional crankshaft 90-degree V-8s, in-line 6s and, of course, V-12 engines. It does not matter if you split the V-6’s crankshaft throws by 30-degrees or whatever, the unbalance is still present. The V-6 is better than an in-line four in balance and refinement though, so for many it has been a suitable choice of engine layout, but for Jaguar? Well, Jaguar had the reputation for the ultimate in refinement at the time. Selecting an engine layout with known imbalance would likely have been dismissed and for good reasons. Remember also, Mundy et al did not like NVH issues or the presence of any noticeable harmonics in the drivetrain. A V-6 has issues in these areas and they are not trivial to resolve. Just as Texans used to “remember the Alamo”, Jaguar’s development group would have remembered the XJ4 torque tube. A V-6 was not on for them.

    Re 60-degree V-8 engine
    These are not balanced. This layout can lead to a successful design (as Yamaha demonstrated for Ford’s Taurus SHO, Volvo’s XC-90, Nobel M600 and all of Yamaha’s own outboard engines ranging from 5.3 to 5.6 litres). Chrysler investigated a 60-degree V-8 based on their Pentastar V-6 but the GFC put paid to that idea unfortunately and so we got lots more of the turbos instead.

    Jaguar’s 60-degree V-8 engine suffered from the same unbalance as all the rest of this type. It is indeed correct that they eventually tamed it, succeeding in all but eliminating the NVH issues (close, but not quite). That victory was mechanically expensive, requiring the elaboration of two balance shafts rotating at twice crankshaft speed. This added weight and significant complexities to the engine. It also added friction (balance shaft drive, bearings for the balance shafts, lubrication supply and so on) and cost in fuel burn. The idea was finally killed off when it was determined it would cost more to tool and build than the V-12 upon which it was based and which was already in production.

    Re limitations imposed upon the V-12 engine by the Radford machine line
    When Jaguar originally tooled up to build the V-12 they set up a brand new line at Radford. It cost them some GBP 7,000,000 or thereabouts. Putting aside the other castings (heads etc.) and focusing solely on the block we find they installed three Cincinnati machines to undertake initial block machining. They also installed three Archdale machines for the remaining machining tasks (drilling, seaming, tapping, milling, boring, decking etc.). The first Archdale had 18 machining stations. The second had 6 stations and the third had 33 stations. At each station a machining task was completed after which the work piece indexed to the next machining operation. A separate machine, the Weatherly horizontal broacher, did sump face and bearing-cap locations. There were also stud insertion machines, nut installation machines and so on. Tolerances were of the order of 38 microns or less. Production capacity was up to 1,000 engines per week if a double shift roster were employed, up to to 180 per week if not.

    …….and then the fuel crisis hit and the economy tanked! New priorities pertaining to fuel economy became the focus. All sorts of political and social forces were unleashed and suddenly the V-12 was not going to sell so very well at all. This led to all sorts of things being worked up (including the 60-degree V-8 and even a two-speed differential unit). One of the most interesting projects was Harry Mundy’s V-12.

    Mundy worked out that a larger capacity V-12 would actually be more economic on fuel than the 5.3 litres version then in production (a conclusion that Alan Scott* of TWR also came to some years later). Mundy (and Scott) added stroke. Mundy developed a mighty 6.4 litre V-12. He used standard block, cylinder heads, pistons and rods from the 5.3 litre V-12. In order to do this he needed a spacer** sandwiched between the heads and block with slightly taller wet liners than stock and several links added to the timing chain (standard was 180 pitches 3/8″ duplex, number added is secret!). This expedient accommodated the extra stroke with standard rods and pistons, neatly avoiding the pistons from hitting the heads. Mundy’s engine was every bit as refined as the original 5.3 litre V-12 (something that is not true for all the other capacity variants of the Jaguar V-12s). Apart from improving the fuel economy the capacity increase really woke the whole show up. The inlet ports worked very well with this rod/stroke ratio. The engine was a lot more efficient and produced a lot more torque lower in the rpm range. So, a lot more performance as well as a lower fuel burn. What’s not to like.

    Alas, there was a problem and the story doesn’t end so well (after all it is Jaguar we are reminiscing about here). When the machines at the Radford facility were installed it had not been foreseen that it may prove necessary to machine a V-engine with a greater deck height. Five and one third litres was already a large engine by the UK and European standards of the time. Adding cubic capacity was not likely to prove to be necessity. That certainly was not a need foreseen. So, it turned out that the architecture of the machines was such that block deck height was one of the dimensions which was hard fixed. As with the bore pitch, it could not be changed. New machines would have been required to achieve a revised deck height dimension.

    Harry Mundy built his prototype on a standard V-12 block taken from the production line. He used a spacer plate and taller liners to accommodate the extra stroke he sought. He used the plate to emulate a block with a taller deck height. When it was discovered that the Radford machines would not allow for a deck height change (the block could be cast taller easily enough, but such a block could not be machined by Radford) he sought a fall back. Why not put the spacer plate into production? This was duly priced up. It would have cost something in the order of a quarter of a million pounds. The management answer was no and so the 6.4 litre V-12 disappeared into history. I have not been able to locate where the car to which it was fitted has gone.

    The point of the Munday 6.4 litre V-12 story is this. Investing in a production facility is very expensive. There are certain restrictions and limitations which will necessarily be imposed on any variant of final product by the nature of the production facility itself. These limitations may come to haunt you in the future, but no-one is omniscient and so one’s decisions have to be made with the best of what is known at the time the decision is made. It is to be recommended that when reviewing past occurrences in car companies due attention is paid to the context and limitations restricting the available “best world” alternatives. Turning now to the XK engine……..


    *Alan Scott was responsible for coming up with the 6.0 litre road-going variant of the V-12. He prepared teh Jaguar V-12 in various other capacities for racing, stating that the ultimate version for Le Mans would have been of 7.1 litres.

    **Lamborghini used a similar approach to expand their V-8 engine cubic capacity. A brilliant variation on the theme was used by Jon Kaase to win the Engine Masters competition using an MEL engine a few years ago. Fascinatingly he was not doing it to achieve extra cubic capacity.

    1. Does anymore information exist regarding Harry Mundy’s 6.4-litre V12 engine? Have to wonder to what degree Mundy was influenced by his own experiences with the design for an all-new quad-cam V6 displacing under 3.0 litres (displacing around 2.6-2.8-litres and putting out 200 hp in normal spec and 280 hp in motorsport guise) during his time at Facel Vega prior to going on to develop the Lotus Twin-Cam?

      Would be interesting to read up more on Harry Mundy if any books exist to complement Walter Hassan’s Climax in Coventry book.

      Have read Harry Weslake also developed a redesigned inlet port for the 2.4-litre XK6 that put out around 170 hp (net), however for whatever reason nothing became of it.

      Can understand Jaguar’s rationale for opting to develop a new engine to replace the XK6, yet part of the problem comes from the unfulfilled promise of the Jaguar V12 that not only could have benefited from further improvement over what entered production had the right calls been made during development, but also in turn could have been a suitable starting point as the basis for a family of related engines (notwithstanding the challenge of Jaguar somehow developing a 90-degree V8 that carries over much of the V12’s architecture – outside of the more exotic 1.8-2.5-litre Coventry Climax CFF/CFA V8 forming the basis of a loosely related suitably enlarged V8).

      To what extent could the XK6 have received the necessary total top to bottom refresh at those windows of opportunity been available and at what period in time until it is in need of replacement? Lean more towards the improvement side of the debate as a consequence of the V12 ending up largely being a White Elephant though ideally would have preferred to see them appear earlier.

  6. Bob

    Context rules everything.

    As Sir William Lyons well understood, Jaguar as a stand alone was dead. Sufficient capital just did not exist for it to continue on as an independent. The problem was acute. Given the nature of the UK at the time, with incessant government tampering and interference throughout industry, society, the finance sector and people’s economic affairs in general, it is something of a miracle that the company survived for as long as it did. The point is that capital was short. Jaguar had an insufficiency of it. As time went on that insufficiency became a larger and larger hindrance to the company until eventually it dominated everything Jaguar.

    The consequence was experienced in engineering and product development. It was possible for Jaguar to continue its lead (for a time) solely by relying on the outstanding capabilities of a tiny group of brilliant engineers and key personnel (one of which was Sir William himself). You could consider this a beneficial inertia effect. It was not sustainable. Trouble was that group was aging, retiring, dying, departing one way or another. Its members was not being replaced like for like. Gradually the pool of people who were “Jaguar” was being diluted. Worse was that Jaguar’s pool of talent was shrinking overall due to (again) capital constraints. All this was bad enough, but there was another much more serious issue arising as the direct consequence of lack of capital. It was in manufacturing and production. Jaguar were never able to solve it and as a result of that the essence of Jaguar was expunged to the point where the organisation which today bears the brand name possesses none of the original design principles or engineering values. (These days they really ought to call themselves something other than Jaguar for Jaguar they most certainly are not.)

    By the late 60s Jaguar could not afford to routinely and consistently upgrade and improve production plant and tooling. They could not afford to improve or change process as and when it was required to so do. That is one of the reasons XK engine production continued on for so long. When the XJ series of sedans was launched the XK engine was old, really old and the form it deployed in for the XJ at (4.2 litres) was a bodge, a patch-up job cobbled together as a necessity in response to what was really an emergency. For the duration of the XJ series 1, 2 & 3 this engine was not replaced because the capital to do so was not available. By the time Jaguar eventually launched the much delayed (and under-developed) XJ40 they needed to make so many alterations to the XK engine design that it was easier to launch with an entirely new engine, the AJ6.

    Jaguar were forced to bet the farm on entirely new engine generations in order to catch the competition. Each time they did it they needed to consume capital, mostly acquired from external sources. They rarely had the budget to improve and develop on a continuous basis. Then, once the new engine was launched, they needed to service the capital they’d consumed as priority and so did not have sufficient resource for continuous improvement. Hence it was a boom and bust process. It was reactive. It was not efficient. It was not effective. This was THE Jaguar problem.

    Turning now to the V-12. That engine was to have been launched with an electronic fuel injection system. It wasn’t. Hence the engine went to production (late) with four Zenith Stombergs- yet another Jaguar emergency lash-up.

    The advent of the US emissions regulations caused a lot of headaches for Jaguar since meeting these rules consumed a lot of resource (capital). One result was a lowering of compression ratios. Another was to influence the decision in favour of not using the Heron combustion chamber for the V-12. Yet another was the elimination of part throttle ignition advance for the export spec V-12. This all had knock on effects. The engine ran hot (a big drawback). Worse was a significant increase in part-throttle fuel consumption. Of course this latter problem was not recognised as a threat since it wasn’t one- well not until the fuel crisis hit and suddenly people were panicking about fuel consumption. Jaguar were wrong footed through no fault of their own. They possessed insufficient capital and resource to quickly adapt. Worse, by then they faced huge political opposition.

    V-12 fuel consumption was on the high side due to a lack of mixture motion in the combustion chamber at part load. This in turn was due to the steep approach of the inlet port (giving fine breathing but little swirl or tumble) as well as the lack of squish provided by the disc shaped combustion chamber. Do not forget that Jaguar were at that time seeking excellence in NVH. For the 5.3 they wanted smoothness above all. Nothing was allowed to excite resonances anywhere! They appear to have preferred the gentle pressure rise provided by the disc combustion chamber because of this. Note that the later HE engines were never as sweet running as the 5.3 flat head engine.

    To remedy the high fuel consumption would require a new head casting allied with new piston design. That would have demanded a development programme to revise cam timing valve size, manifolding, fuel injector timing and size etc. etc. etc. Then they would have needed new tooling and new production process. That would have to be developed, tested out and commissioned etc. They would have had to develop and test and revise for NVH. There just wasn’t the capital available to do any of it at the time. They knew what the engine needed and what they needed to do but they just couldn’t.

    Mundy’s approach for the 6.4 was to use as many standard parts as possible. He understood that by providing more torque at lower rpm there would be less friction drag in the engine. He realised that a bigger stroke would provide a sharper activation signal to the inlet port earlier during the inlet stroke. It would also provide higher mixture velocity, hence more mixture motion. Thus he could rectify some of the problems the engine suffered in 5.3 litre form.

    Building Mundy’s V-12 @ 6.4 litres
    It is remarkably easy to erect one of these. It uses standard pistons, rods and cylinder heads. Extra links are added to the timing chain to accommodate the extra distance between sprockets caused by the spacer plates (which are easily milled these days on a CNC machine). Liners are non-standard and need to be a little taller or you can put spacer rings at the bottom of each parent bore and employ standard liners – your choice. Cams are standard (which you can regrind should you be so inclined). Buckets and shims are standard. You need a new crankshaft. This is where the major expense is. There are two options. Billet is better. Get Krem Performance to have a US crank grinder machine up some 4340 billet to Krem’s Group44 specification. Choose the 84mm stroke option. Alternatively you could contact Bill White in NZ. He can do whatever you require for the crankshaft (even a casting!).

    Re 90-degree V-8
    This was never on the cards. There was no budget to build one, let alone tool up for it. Such an engine would have demanded a separate machine line for a start. Any similarity between a 90-degree V-8 and the 60-degree V-12 would have been coincidental. Besides, Jaguar management understood that a V-8 would not be as refined as a V-12 (and they never really are). They also understood that the US had plenty of well developed V-8 engines. Doing yet another V-8 would not give them any USP whatsoever.

    Re development possibilities
    Pretending that Jaguar had the capital to do whatever one wishes, what would be the best response to the situation they were in? Reduce bore and stroke of the V-12 to yield a 4.2 litre version. Radford stays fully busy….


    1. Yep. That about nails it, JT. The Jaguar enigma in a nutshell.

      Harry Mundy’s daily driver at the time was a prototype XJ4 fitted, both with the 6.4 V12 and the five speed manual gearbox which he also oversaw. That car was allegedly, quite something. I have heard mutterings that it has survived.

      But then, a lot of quite interesting things were concocted at Browns Lane – very few seeing the light of day. Sadly.

    2. Thanks J T

      Read Jaguar as one of those companies that heavily relied on used or knackered tooling from the likes of Standard and others to build their cars, some of which were reputedly even utilized until Ford acquired Jaguar. All things considered it is indeed a miracle the company managed to survive for as long as it did, especially under those circumstances.

      Know Jaguar were in a position where they could not survive on their own despite talk of going down such a risky path in Lyons biography had his son lived (who seem to be out of his depth has far as succeeding his father was concerned prior to his accident), with only BMC or Leyland to choose from. One could say Jaguar ultimately choose the least worst option of the two yet could see them faring better with the other option had circumstances been different.

      Unfortunate the Jaguar V12 never merited the AE Brico electronic fuel injection system as a result of Rolls-Royce going bust, the likes of Rover and others were also casualties of Brico not entering production.

      In terms of output and more how does Harry Mundy’s 6.4-litre V12 compare to the 5.3 and 6.0 V12s?

      Can understand Jaguar’s reasons for not developing a 90-degree V8, that said it could be argued that its higher sophistication compared to what the US had at the time (up until about the 1990s) would more than make up for its perceived lack of USP in terms of V8 layout being less refined compared to the V12.

      There was a large void between the 6-cylinder (including 4.2-litre bodge) and 5.3-litre V12 engines that Jaguar’s upmarket rivals were more than happy to capitalize on as its expense, though have understood Jaguar’s original intentions were to move upmarket towards the 60-degree V8/V12 and move away from the 6-cylinder engines they were known for, with the flaws of the 60-degree V8 and chaos at BMC/BL leading them to the situation they found themselves in. Despite its own problems perhaps a development of the (allegedly 1st gen Chrysler Hemi V8 influenced) Daimler V8 from 2.5-4.5-litres to 3.0-5.0-litres would have provided the most expedient remedy, though it is hardly ideal compared to an in-house design.

      In terms of development possibilities it is not so much pretending Jaguar actually had the capital to bring such experiments into production, more about seeing what else was in the cupboard and what other paths the company were experimenting with historically speaking.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: