To mark the 30th anniversary of XJ40’s launch, we speak exclusively to former Jaguar Engineering Director, Jim Randle.
If the XJ40-series’ legacy represents a series of lasts, then chief amongst them is that it remains arguably the final mainstream British series production car to embody the single-minded vision of one man. Because if a car could embody the personality and mentality of its creator, then XJ40 is Jim Randle, whose stamp is all over its conceptual and engineering design. Recently Driven to Write spoke exclusively with the father of the ’40 to re-evaluate the final purebred Jaguar saloon.
A lot of early XJ40 work took place under Bob Knight during the 1970’s and I wondered how much of that carried forward to the car Randle developed from 1979 onwards. “I’d already been working on the car, developing suspensions [and] crush structures with Bob Knight. For that period, Bob was diverted anyway due to BL issues, so, I had it to myself.”
Randle then goes on to explain how the early stages of the car’s development became dominated by regulatory imperatives. “The key thing surrounding legislative requirements – one of which is crash performance – the structure had to be right in that respect. I did a lot of work in that area. We didn’t get it very far wrong on XJ40. We got it much better on later projects, when I understood it better.”
The subject of crush-structure is apposite however, as there are a number of myths surrounding XJ40 I’m keen to address. One of them I put to Randle is that the crush tubes were said to be purposely designed to entail the exclusive use of Jaguar’s in-line AJ6 engine, is this true? “It wasn’t crush tubes. Our friends at British Leyland wanted us to drop the AJ6 engine and put the Buick [Rover V8] engine in. So I developed a story which said: ‘look, we’ve done a lot of crush work’ – it was the structure going back into the bulkhead, which I’d got a very nice, square-ish box – I said: ‘We’re going to have to do it all again, because if that key stress carrier is changed, that’s going to be a big job; we’ve got to rethink the structure.’ Which is bullshit of course, but they swallowed it.”
The AJ6 engine was of course a key component of XJ40, designed to be lighter and more efficient for a new more austere landscape, one where big-engined luxury saloons seemed doomed. Today Randle is a little ambivalent about its merits. “Harry Mundy did a very good job on AJ6 and it was pretty bullet proof, [but] I think in principle, in terms of refinement, we made a mistake in having an inline aluminium six. A V6 would have been the more sensible project.”
He goes on to explain. “Six inline engines, aluminium block engines, are a bit of a problem, because the crank produces secondary forces which are resisted by the stiffness of the block. Aluminium blocks are not as stiff as a cast iron block, they don’t have the damping a cast-iron block has. A cast-iron crank is better, because it has its own internal damping, therefore the secondaries are not so bad. But we did have problems with the AJ6 in that respect. The problem is that the secondary forces being developed at the tail shaft go straight into the floor, which is a big sounding board. It’s quite an issue with that model, but we solved it with our mounting system.”
The AJ6 engine was initially conceived on the basis that it could be derived from existing V12 tooling – a process which took the powertrain team down some fruitless alleyways throughout the 1970’s. One in particular being the stillborn 60° V8. I’m interested in Randle’s view of its deficiencies.
“What happens with V8’s is that you get a 90° shift in the position of the crank; it’s got 90° intervals, and the block is set at 90°. That means you can get most of the problems out of it. Flat plane cranks and V8s don’t go well together, [they] run like four closely coupled Harley Davidsons. The 60° V8 was effectively a 2/3rds length V12. The only problem we had with the V8 in that form was the firing order down each bank was uneven because it had a flat plane crank. With a flat-plane crank, it just sounds like a big four [and] it did sound like a four. It also had secondary difficulties, and to overcome that, we were running a couple of twice-engine speed counterbalance masses alongside the thing. It wasn’t a nice engine, so we dropped it. Flat-plane, 60° V8s; there aren’t many of them and there’s a good reason for it!
Later XJ40 models came with a longer stroke four litre version of the AJ6. Was this a superior power unit? “It had better performance. [The] 3.6 litre had a cast crank, [the] 4.0 litre a forged crank. I think the 3.6 is more refined than the 4.0 – a lot of that is probably to do with the cast crank.”
Following his departure from Jaguar, a V12 installation was completed, following lengthy delays involving (again) the front structure of the car. Randle’s position on this skewers another sacred cow. “I really don’t know why they did that, [it] seemed illogical to me. If you wanted that power out of an AJ6 engine, you’d only have to turbocharge it, and you’d go way past what the V12 would produce.”
Something of course he could prove given that twin-turbo AJ6 engines were routinely producing well over 300 bhp in prototype form. But at the other end of the performance scale, Randle doesn’t believe the small capacity engine had much to commend it either. “Early XJ40s had that in – a 2.9 litre inclined engine. It was okay in terms of refinement, but it hadn’t got the power and performance.”
This engine of course featured a similar Michael May ‘Fireball Head’ to that developed for the V12 and its claims for ‘High Efficiency’ also receive a debunking. “It didn’t deliver its promise. It was going to be 13-14:1 compression ratio, and therefore it should have delivered more power and better economy. It didn’t really deliver that, and we finished off by nearer to 10:1 than the 13-14:1 that it promised. Expansion ratio is everything, so no, it really didn’t deliver too much.” With some mirth, he adds: “You know, the bullshit of putting H.E. on the back, I think, was probably as valuable as anything!”
Part two
Driven to Write thanks Jim Randle and Christopher Butt of auto-didakt for their kind assistance with this series.
©Driven to Write. All rights reserved. This article may not be copied, republished (in full or in part) or used in any form without the written permission of the author.
Driven To Write 
Thank you Eóin and Jim for this. I’ve read the article over several times and my only complaint is that there isn’t far more of it.
There are insights into Jaguars engines strategy I haven’t read anywhere else, paricularly Randle’s inclination towards a V6 rather than an in line engine. From Jeff Daniels’ book I recall that the idea of a V12 derived V6 was killed off by snobbery in the mid-late ’60s – such things were fine for Fords and Buicks, but not for Jaguars.
The insight into why cast iron would have been more appropriate for a straight six block than aluminium are particularly pertinent as we await the arrival of the six cylinder Ingenium, an all-alloy unit much less generously proportioned than the AJ6/16.
Agree, stunning article. It’s quite a scoop….
On the V6, I can agree to the snobbery. Except for the Italians, most V6 engines of the first generation were quite crude affairs. Italy had their Lancia, Dino, and later Alfa V6-engines. But they were quite a different thing from the Ford V6-engines of the day. What’s fit for a Transit isn’t really fit for a Jaguar. It wasn’t really until the 80’s and 90’s the V6 was developed enough for mass production use to be a viable alternative to a straight six.
Yes, we’re very pleased Jim agreed to talk to us. Listening to him was fascinating. The interview will run as a series in four parts over the coming weeks, focusing on different aspects of the car’s development.
I didn’t get a sense that there was a great deal of snobbery involved – certainly not in his case and I can’t imagine Harry Mundy, (especially from what I’ve heard about him) being much a snob either. Jim did have some interesting things to say about V6’s however, but one can’t include everything.
I would suggest – from my understanding of the history books – the problem with halving the V12 either lengthways or sideways was always one of swept volume. You simply wouldn’t have a powerful enough engine – not without forced induction anyway. The slant six idea I believe stemmed from an experiment where a V12 was sliced lengthwise. This, coupled with the results gleaned from Mundy’s 24 valve alloy XK unit formed the genesis of what became AJ6. Throughout this period Jaguar’s engineers were having to be reactive in their thinking. On one hand you had regulatory pressures and the fuel crisis. On the other, they were hamstrung by politics and beer-money budgets. The V12 was a magnificent engine, but it was the wrong one in retrospect – largely because its layout didn’t give them the flexibility to downsize.
Had Jaguar’s profits (and they were still profitable well into the ’70s) not been poured into the bottomless pit at Longbridge – (a matter confirmed by Bob Knight) – Browns Lane engineers may have taken entirely different powertrain approaches. Jim certainly did the following decade, but that’s another story.
Like Robertas I read this through a couple of times. Brilliant stuff, roll on next week.
I’m not going to comment on the contents of the article, I just wish to extend my thanks for the publishing the piece and I look forward to the forthcoming instalments.
Terrific!
I’ve had another read of the relevant sections of the Jeff Daniels “The Engineering Story” book and the timelines are interesting. There was a project for a “3 litre production engine” given the code number XJ18 in 1966. Daniels is uncertain whether this is a small capacity XK or a new engine.
Elsewhere he states that the Radford V12 transfer line had been commissioned to handle a slant-6, and when development of this engine was abandoned in May 1971 the facility was “doomed to under-utilisation”, and was failed ever to pay for itself. Reading such things, I wonder why Jaguar didn’t fit better into British Leyland than it did.
The 60 degree V8 was finally ditched in late 1971. That date is interesting as the V12 had been on sale since April of that year in the E-Type Series 3. It ties in with a report I read in the Daily Express not long after the XJ6 launch about “a new family of V8 and V12” engines which would eventually power the new car. The UK dailies were far less discreet than the motoring titles about embargoed information or stories told in confidence.
Putting two and two together and possibly making five, it suggests that the V8 was being considered as a serious XK replacement. This is borne out by the considerable efforts which went into trying to make it work.
Daniels infers that development of the ‘slant-6’ began when the V8 was abandoned, and that “there is no evidence the V6 was ever taken seriously”. This makes the Jim Randle comments on his preference for a V6 over an-line engine all the more intriguing. I suspect that there is a crash safety element to his. A long, heavy, longitudinally mounted in-line six, is an engineer’s nightmare in this respect. A V6 or V8 is far more manageable.
Is there anything on the cutting-room floor which would confirm or deny these notions?
Robertas: Again, from the reading I’ve done on the subject, the 3 litre engine was a version of the XK intended to be the mainstay power unit for XJ4 – which was launched as the XJ6 in 1968. I’m unclear whether this was to retain a cast iron block or to have an alloy one – most likely the former. Prototype XJ4’s were running with this engine in both manual and automatic form until quite late into XJ4’s development with Bob Knight’s problematic torque-tube double wishbone rear suspension. The story goes that the 3 litre was beautifully smooth-running but was found wanting in terms of torque and with the V12 being delayed by Brico’s decision to abandon its fuel injection installation, it was decided to (hastily) co-opt the existing 4.2 litre – which was a taller power unit than the 3 litre (or the V12) and therefore necessitated the power bulge on the bonnet which Lyons detested so much. This was to be a temporary measure but of course lasted right until the advent of XJ40 in 1986. What few realise is how much of a compromise the XJ ended up being. Little of its intended technical specification made it into the car that launched well over a year late in the Autumn of 1968.
The 4.2 was to be swiftly replaced by the V8 derivation of the 12 which was schemed to replace the XK unit and did seem to be an open secret. Despite some within the powertrain team suggesting the engine was just about debugged once fitted with twin balance shafts, Bob Knight simply wouldn’t countenance an engine so compromised from an NVH perspective. But moreover, BL would have been unlikely to sanction it – not with the Rover and Triumph units already to hand. Once this engine programme was cancelled, Jaguar were forced to try and get some return for the massive investment in tooling for the V12. Hence the shaved six, the two speed axle and ultimately the ‘May head’.
From Jaguar’s perspective, given the sort of cars they were producing, an engine with less capacity than around three and a half litres was not going to give them the power and torque they required, which surely doomed the V6 idea as much as any other factor. Let’s not forget the 2.9 litre version of AJ6 was deficient in this area as well.
After we’ve been considering XJ40 on these pages and others for so long, it’s fascinating to get a first hand account. It’s also interesting to read Professor Randle on the V12, both clarification of the semi-myth that ‘they deliberately made the engine bay so that it wouldn’t take the Rover V8′ and his questioning as to why they fitted the V12 anyway. That sounds like a rational (and I’m sure correct) engineer’s judgement that doesn’t factor in the irrational longings of un-tutored engine snobs such as myself, though since it was only in production for just over a year in XJ40 form, I’ll admit that its existence seems even more irrational.
It’s a matter of marketing. The V12 race was on, thanks to BMW’s success with the E32 750i(L) and Mercedes’ V12 to end all V12s in the W140 600 SE(L) model. At the same tome, the Lexus LS400 had become the class standard after its launch in quite a few regards, but the Europeans still considered themselves to be the prestige choice – not least because they were offering V12s.
There may have been no sound engineering argument on behalf of Jaguar’s 6.0 V12, but such an engine may well have been considered necessary to join the European luxury saloon club.
To this day, some enthusiasts keep on praising it, simply because it was Jaguar’s most powerful V12 engine. That it failed to live up to its predecessors’ standards in the one area it was intended to excel (NVH) only goes to show how little some people care about actual qualities, as long as they’ve got figures to boast about.
“Four closely coupled Harley Davidsons”
I like that – V-Rods presumably…
Split crankpins hadn’t been tried on production car engines in the early ’70s, but they might have been the salvation of the 60 degree Jaguar V8. Ford (or more likely Yamaha) used them, along with balancer shafts on the Taurus SHO V8. I can’t find proof positive, but I’d be surprised if the snappily-titled Volvo B84444s engine, also built by Yamaha, didn’t apply the same nostrum.
There was another 60 degree V8, built not far from Coventry at Acocks Green. I wonder if Harry Mundy or Bob Knight ever sought the advice of their Leyland colleague Gordon Bashford, who was involved in converting the Rolls Royce Merlin into the V12 Meteor and V8 Meteorite.
I suspect that the 60 degree V8 was just too contrived and contrarian for Jaguar, who were very classical and high-minded in their approach to engine design, as befits a grand marque.
If anyone is as curious as I was about the German-language blog post that’s linked to in this article, I had my brother produce an English translation that I’d be happy to share.
Thanks for that. I read about the decline in German in the UK secondary and third level education. Being able to read German (mine is a bit feeble) is a great window on a fascinating culture.