Jaguar XJ13

Recreating a 20th century car using 21st century technology

Neville — Sun, 01 Apr 2012 02:11:00 +1000

As stated earlier in this blog, my intention is to create a facsimile of Jaguar's unique XJ13 - as it was in 1966/67 and before it was rebuilt in 1972/73. It had to be rebuilt after it was badly damaged on the eve of its first public appearance in 1971. My aim is to recreate the car as faithfully as I am able and as a tribute to the genius of its designer, Malcolm Sayer.

During the rebuild by Abbey Panels in 1972/73, certain aspects of the car were altered and it lost its "pure" form as originally envisaged by Sayer. One of the more obvious "enhancements" was the addition of flared/widened wheelarches. The XJ13 log records this was done primarily for "cosmetic reasons". Earlier entries in this blog describe some of the major differences between the car I want to recreate and the car as it stands today.

Undoubtedly, the current car is unique and has continuous history linking it back to the one and only original. It may have been described as a, "Jaguar-built replica" by authors Viart & Cognet in their 1985 book, "Jaguar - A Tradition of Sports Cars" (page 318), with forward by William Lyons himself, but I personally feel this may be a little unfair as most of the underlying structure was salvaged and re-used (with the exception of certain floor and sill sections - the original sections were originally painted black and are likely to have been been replaced). The engine installed in the car today is a different engine to the one originally installed in the XJ13 in the Spring of 1966 but it remains one of the very few prototype quad-cam engines that have survived and was installed in the car in period. OK, the body may be completely new, and different in some respects to the original body, but there can be no doubt that the car gracing the Jaguar Heritage collection can describe itself as the unique Jaguar XJ13.

What I am attempting to create can only ever be a facsimile and homage to the original XJ13 and its designer Malcolm Sayer. There is, and always has been, one Jaguar XJ13.

So - how to set about recreating a car which doesn't exist anymore?

Contrary to what you may read from certain replica manufacturers over the years, there are no "blueprints" for the car. Jaguar, on their part, have never allowed sufficient access to the car to enable detailed measurements to be made. Again, this is despite statements to the contrary by certain replica builders. Indeed, a replica made by the very talented Rod Jolley which passed into the hands of the late Jaguar Specialist Tim Waddingham, bears a brass plaque claiming the replica was produced "with the co-operation of Jaguar". The inaccuracy of the replica compared to the original bears testament to Jaguar's unwillingness to allow intimate access to the car. The closest anyone got to the car may have been Bryan Wingfield whose car eventually ended up in the Walter Hill Collection. However, this car was notoriously "wrong" in may details - including a rather "snub-nosed" appearance. The latter does indicate how difficult it is to replicate the complex curves of the car simply by reference to photographs - even with privileged access to the car itself and for a man with undoubted car-making skills.

OK - there are no "blueprints" and no chance Jaguar will allow sufficient access to the car so where do you go from here?

Fortunately, Jaguar Heritage very kindly granted me access to XJ13-related documents in their archive. However, although the archive is now professionally managed by Anders Clausager and his team, this has not always been the case in the past and many documents may have gone missing in the intervening years. Although Jaguar Heritage's archived documents give valuable clues to the car's build and history, I have had to dig deeper and extend my search further afield. A breakthrough came the best part of a year ago when a collection of original documents came to light containing actual data describing the original car's construction. This has since been supplemented by previously-unpublished photographs taken during the car's build in 1965/66. It is my wish to eventually deposit these documents in the Jaguar Heritage Archive for the benefit of future historians.

What are these documents exactly?

These documents contain critical measurements used by Jaguar to build the car. They are likely to have originated from Malcolm Sayer himself. Just to explain ...

Malcolm Sayer, as I reported in a previous post (Designing the XJ13) was very much a man “ahead of his time”. There is much talk nowadays of Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) but it seems that as early as the 1950s Sayer had developed his own longhand version of similar techniques. He kept his calculations and means of representing complex shapes mathematically very close to his chest and there is little information on his methodology available today. Paul Skilleter reported that Cyril Crouch, who worked in the Body Drawing Office in Sayer’s time, recalls him “using Chambers seven-figure log tables to calculate all the shapes, as one would do on a computer now.”

In essence, these documents consist of a mass of numbers defining fixed points in 3D space. For example, a particular single point on a body surface can be defined as:

"X inches from an origin on the floor at the front of the car; Y inches up from the floor; Z inches from the centreline of the car"

As an example of data for one part of the car, the following original document indicates how the curvature of the windscreen was defined.

Original data - definition of outer windscreen surface.(Data obscured). © Jaguar Heritage - reproduced with permission.

At the start of my project I discovered that Pilkingtons claimed to have located the original metal jig used to manufacture the original 1966 XJ13's windscreen. (see earlier blog entry Triplex Laminated Windscreen. I commissioned a windscreen from them and this gave me a unique opportunity to objectively validate their claims against the original data. The finished windscreen was digitally scanned by Stuart Brown of 3D Engineering and it's precise shape was captured.

Digital scan of windscreen made using Pilkington's original XJ13 windscreen former.

Stuart then superimposed the 3D points defined in the original Jaguar document. He was then able to carry out a statistical comparison of the two sets of data. During this analysis he discovered that Sayer had defined the windscreen as sitting a rather strange 32.39 degrees from horizontal. The conclusion was that Sayer found, "wherever the windscreen laid within his overall body profile was correct". More detailed analysis by Stuart showed a close agreement between the windscreen Pilkingtons had produced and the original Jaguar data. The following picture shows the variance between points on the two defined surfaces - the closer to red, the bigger the difference:

Comparison of the new windscreen vs original Jaguar data.

The data is shown below:

MAXIMUM DISTANCE: +1.79mm -2.18mm
AVERAGE DISTANCE: 0.06mm
STD DEVIATION: 0.30mm

In short, there is an average of 0.06mm difference between the new screen and the original data - pretty good don't you agree?

This was very good news for me as it meant we could precisely locate a key section of the outer body. But more was to follow .... similar data describing original car's body shape, as well as data precisely identifying key location points for things such as steering rack, front and rear suspension, suspension arms, shock absorbers etc etc was uncovered. The latter data has proved especially invaluable in the design and ongoing build of the complete chassis/monocoque unit.

Here is an example of the type of data that shows where key components are located. It shows the precise location of the XJ13's upper front wishbone (wishbone as used in the 1964 Lightweight E-Type Jaguar). I have obscured the actual 3D data points.

Original document describing location of upper front wishbone in 3D space.

The above data doesn't only describe exactly where the wishbone should attach to the chassis, it also gives valuable information on the dimensions of the chassis itself. Combining data such as this with original photographs such as the one shown below allows us to precisely model the front suspension. Whether or not we will choose to copy the rather poor quality of welding remains to be seen ....

Front chassis.

Putting all this data together, along with other measurement data and contemporary photos taken during the car's build have enabled us to arrive at an excellent digital CAD representation of the 1966 original. This data has been further enhanced by discussions with those who were present and participated in the original build.

So - where to from here?

All the above data has been used to enhance the digital model of the 1966 car. Gradually seeing the 1966 car emerge from the data has been a rather exciting process. The first physical manifestation of the digital data has been the manufacture of a full-size buck which is being used to manufacture the car's monocoque. Pictures of this buck can be seen in a previous post Building the Chassis/Monocoque. We have decided to build the monocoque in steel first, just to "get it right". This all-steel monocoque will then be destroyed and we will build one using original-spec aluminium and steel as original.

At the same time, work has been continuing on the buck which will be used to form the outer body panels. The picture below shows some views of the "virtual CAD buck" as it looks today.

Before I finally press "GO" and have the body buck manufactured, I have commissioned a pair of 3D-printed models of the body - one in 1:18 scale and one in approximately 1:30 scale. It is all very well being able to see the finished car on a screen but I wanted to have something I could hold in my hand. I plan to paint the larger of the two so I can see how the light catches it and how the curves measure up to the original. First impressions are very favourable

To be continued ....

The West Yorkshire Foundry

Neville — Sun, 12 Feb 2012 00:30:00 +1000

Whilst researching people, places and events surrounding the XJ13 I came across references to the West Yorkshire Foundry.

Who are they ... do I hear you ask? For the best part of 100 years the Foundry was responsible for the casting of cylinder heads and blocks for the British automotive industry. Have a look on practically any cylinder head or block made in the UK in the last 60 years and the chances are you will see the initials "WYF" cast into the block and/or head. For example, the following initials are proudly displayed on my prototype quad-cam engine block:

Prototype V12 casting marks.

The West Yorkshire Foundry emblem can be seen as an intertwined "W" and "Y". The other characters refer to the material of construction (LM8), Jaguar's experimental identification (XW 5014) and Part Number (C2020). If you look at more recent Jaguar blocks, the West Yorkshire Foundry initials are even more prominently displayed as shown on this SOHC V12 block from the 1980s:

SOHC V12 casting marks.

The West Yorkshire Foundry has had an association with Jaguar from the days of the SS Jaguars right up to the first years of the 21st Century - not only supplying castings for Jaguar's production cars but also one-offs and small runs for things such as the initial run of 10 castings for Jaguar's "XJ6" quad-cam V12 engine project (not to be confused with their later saloon of the same name). The supplied bare castings for the racing engine project were delivered to Coventry Climax in 1964 for final fettling before being delivered to Jaguar's Experimental and Competition Departments for assembly and installation.

Watch almost any programme or film on TV and you will see something that was made by the West Yorkshire Foundry - Aston Martin, Rolls-Royce, Jaguar, Rover and many more.

Having found almost nothing in print about the West Yorkshire Foundry I set about trying to learn a little more about them and their association with Jaguar. I had visions of perhaps stumbling across casting patterns and records of correspondence between the Foundry and Jaguar - perhaps even from the times of Jaguar's Le Mans successes in the 1950s through to the XJ13 project itself? These initial hopes were soon dashed when I discovered the Foundry had quietly closed in 2004 with almost no trace of its former existence to be found.

This is what is found if you visit parts of the site of the foundry today:

The West Yorkshire Foundry today.

Even more poignant if you superimpose a picture of a group of workers on a picture of some of the remaining original buildings:

What had happened to all those moulds, patterns, drawings and historic correspondence? It seemed that nothing had survived. I continued my search and , at the start of 2010, came across a website - www.fettling.com. The website reads,

A book "Meltdown – Words and Images from a West Yorkshire Foundry"
An exhibition – which is touring the Leeds area.
A DVD of the short documentary film about the foundry - Cast Well and True."

The book, "Meltdown" and DVD referred to above are available from:

Heads Together Productions, The Media Centre, 7 Northumberland Street, Huddersfield HD1 1RL E: adrian@headstogether.org

Leeds Industrial Museum, Armley Mills, Canal Road, Leeds, LS12 2UF T: 0113 263 7861 E: www.leeds.gov.uk

Waterstones, Albion Street, Leeds, LS1 6HX T: 0113 242 0839

The Round Foundry Media Centre, Foundry Street, Leeds, LS11 5QP T: 0870 420 2300 E: info@roundfoundry.net www.roundfoundry.net

"Meltdown - Words and Images from a Yorkshire Foundry"

The book and DVD do provide a fascinating glimpse into the day-to-day life and individuals who worked at the Foundry. Thankfully, someone had the foresight to preserve at least some images. The website also provides a forum connecting past employees and my research continues with surviving foundry-workers (bearing in mind the prototype engines were made almost 50 years ago!).

For now, here are some glimpses into the last days of the Foundry as shown in the DVD. I don't know how many copies of the book are left of whether there is enough interest to justify a reprint but I do recommend you add a copy to your personal library while you still can. It is currently on sale for a very reasonable £10.

Here are some excerpts from the book that accompanies the DVD:

"The Clarence Road Foundry was part of Leeds' manufacturing heritage for many years. Its closure brought to an end another chapter in our industrial history.

Engineering is concerned with the transformation of energy and the manufacture of industrial engines and power driven appliances. Defined in this way, Leeds was a pioneering city in the late eighteenth and nineteenth centuries. Millwrights were the earliest mechanical engineers, concerned with such 'prime movers' as water mills and waterwheels. By 1820, the steam power revolution was well underway in Leeds, thanks to its textile mill owners harnessing their operations to the ideas of inventors like Thomas Savery (1650-1715), Thomas Newcomen (1663-1729) and, more importantly, James Watt (1736-1819)...

... by 1938, the derelict foundries in Sayner Lane were occupied by the Airdale Light Alloy Company ... one source suggests that the Airdale Light Alloy Company had been given a small contract to manufacture aircraft parts, but could not meet the Ministry's tight deaadlines; as a result MAP asked Leyland Motors to step in and manage the foundry ... there was a distinct shortage of carburettors for the Rolls-Royce Merlin engines, which powered both the Spitfire and Hurricane fighter aircraft, during the Battle of Britain ... Leyland sent a small team of foundry specialists to Leeds ... in March of 1942,... the total weight of carburettors produced was less than that of other castings. He (Mr West of Leyland) was beginning to feel his task was completed ... by the end of the war it is probably true to say that many, if not all the carburettor bodies flying for the RAF had been made in Sayner Lane ...

The last tank produced at Sayner Lane by Leyland Motors - © British Commercial Vehicle Museum

... the resurrection of the wartime foundry in Sayner Lane, Leeds, as West Yorkshire Foundries in 1846 is closely linked with the development of the British Motor Industry in the second half of the twentieth century ... between 1948 and 1951, domestic sales accounted for less than 30% of the output of private cars and only 45% of commercial vehicles. The British Automotive Industry had become one of the world's key exporters of motor cars. It was into this favourable economic climate that the foundry at Sayer Lane emerged as a manufacturer of high quality iron and aluminium castings for cars and commercial vehicles ... rumour has it that, after the war, MAP sold the Sayner Lane Foundry to Leyland Motors for one pre-decimal penny as a gesture of gratitude for the Company's efforts during the war ... by 1961, production at West Yorkshire Foundries had reacged 120 tons of aluminium per week and 600 tons of grey iron ... the physical expansion of the plant was enormous, growing from 7,300 square yards in 1946 to 48,000 square yards in 1961 ... The Company, by 1961, employed 2,000 people to make 14,000 different parts for the domestic motor industry ... West Yorkshire Foundries supplied most of the motor manufactureres in Great Britain with cylinder blocks and heads ... Jaguar bought over thirty separate parts for their specialist car market and headed a list of customers which reads like a Hall of Fame for British car manufacturers ... in 1966 ... the West Yorkshire Foundries built a new state-of-the-art gravity die-casting foundry ... the main Aluminium Sand Foundry was producing the six cylinder heads for Jaguar and Rover ... Walter West retired from the company in 1969, and left behind a prosperous and expanding business ...

1954 advert

... however, sooner than West or anyone else could have anticipated, the cold blasts of merger, rationalisation and recession would be whistling at the foundry doors in Sayner Lane ... in Britain, output of vehicles per employee per year became an embarrassing statistic. The British needed 67% more labour to make a Ford Escort than the Germans, and 132% more than the Belgians to make a Mini ... as a result of a series of mergers and acquisitions, in 1962, Leyland Motors Limited became the British Leyland Motor Corporation; operating on sixty different UK sites - West Yorkshire Foundries being one of them ... British Leyland faced a serious cash-flow crisis and were forced to turn to the Government of the day ... Leyland were in a fight for their very survival ... under pressure from Margaret Thatcher's 'belt-tightening' Government, Michael Edwardes announced a long-overdue restructuring of British Leyland ... following an internal review of management and staff, the future of thirty Leyland sites was still in the balance; West Yorkshire Foundries was one of them ... in 1982, British Leyland was renamed the Austin-Rover Group and the foundry at Leeds continued to act in a limited way as a supplier of high-cored cylinder blocks and heads to the automotive industry ... (in) 1985/86, West Yorkshire Foundries was sold to a private German company (Eisenwerk Bruhl) ... Yorkshire Foundries changed its name to VAW Motorcast Ltd and flourished after 1997 ... in 2002, West Yorkshire Foundries once more faced the prospect of new owners (later to become Hydro Aluminium Motorcast Limited) ... within eighteen months ... Hydro decided there was too much capacity in the automotive cylinder head and block market and a worrying lack of orders beyond 2004 ..."

Announcement by Hydro Aluminium Motorcast

... by 2005, the foundry buildings in which they (the workforce) and generations before them had laboured, would be silent, empty and unused ..."

New-Old-Stock

Neville — Thu, 12 Jan 2012 22:15:00 +1000

It never ceases to amaze me just how many original parts and original unpublished accounts/documents still turn up for the XJ13/quad-cam engines after so many years. Recent discoveries have included a complete set of UNUSED inlet valves for the quad-cam heads as well as previously undiscovered photos taken at the time of the original build in 1965. I can add these items to the growing list of items that have surfaced - including an original-spec ZF "Dash 1" transaxle which was still in its crate from the 1960s. The transaxle is currently being rebuilt and will incorporate changes made by Jaguar for the original XJ13. This includes using a pair of ORIGINAL XJ13 driveshafts used on the XJ13 during its development. I need to research a little further but it is entirely possible these driveshafts were in place when David Hobbs set the UK closed-circuit record of 167.5mph in 1967.

The picture below shows the 1 7/8" "new-old-stock" inlet valves (in pride of place on a table in my living room - much to my wife's disgust ...)

"New-Old-Stock" V12 quad-cam prototype engine valves.

Two original high-resolution photos have recently come to light (the photos below are low-resolution for the web). They were taken during the build of the original in 1965 and give valuable details which will be faithfully incorporated in my recreation. The first shows the rear view of the monocoque and shows how the engine mounts were built up. A wooden "jig" can be seen which was used to locate the engine mounts. The left-hand sill is where the dry sump oil tank will sit. The large circular opening gives access to a rubber oil tank that sits inside the sill.

H1965/66 original XJ13 - rear monocoque

This second picture gives more detailed clues of the front monocoque construction. Note the similarity to the 1964 Lightweight E-Type.

H1965/66 original XJ13 - front monocoque

Here is a picture from a little while ago of the heads which will become the valves' new home. The heads have been stripped, thoroughly examined and skimmed by a few thou. Pressure-testing confirmed the heads' integrity. All guides are within tolerance and the valve seats were found to be securely fixed in place. The guides and seats will not be replaced although two exhaust valves (very slightly out of true) and all valve springs will be replaced.

Heads stripped for inspection.

How is the body coming on do I hear you say? Here is a sneak preview of the millimetre-perfect outer body as a digital image.

Body surfaces - 1966 XJ13 (as intended by Malcolm Sayer and as originally constructed)

The next picture shows how the digital model compares to the 1966 original. The most striking feature is how Malcolm Sayer's original XJ13 design in the wheelarch area follows a similar pattern to the D and E-Type (rather than the "1970's flared arches later added by Jaguar).

Body surfaces - compared against 1966 original.

XJ13 - The Book

Neville — Sun, 18 Dec 2011 02:33:00 +1000

On Friday, 16th December 2011 a small group gathered around the XJ13 at Jaguar Heritage to mark the launch of Peter Wilson's book, "XJ13 - The definitive story of the Jaguar Le Mans car and the V12 engine that powered it".

This was no ordinary gathering, as those present included many surviving members of the team that were originally involved in the original XJ13 car as well as the development of the engine that powered it. Those present included Norman Dewis, George Buck, Frank Philpott, Jim Eastick, Ron Greves, Mike Kimberley, Roger Shelbourne, Robert Berry, Peter Taylor and Peter Wilson himself.

Click the images below to see videos and more detail of the proceedings

The videos include introductions by Tony Duckhouse (on behalf of Jaguar Heritage), Paul Skilleter (renowned Jaguar author and publisher) and further insights by Mike Kimberley (XJ13 Project Manager - later to join Colin Chapman and become CEO of Group Lotus):

More details of the book itself are available from Paul Skilleter Books or the Jaguar Clubs of North America.

Building the Chassis/Monocoque - Choice of Materials

Neville — Sun, 20 Nov 2011 17:59:00 +1000

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As the build of the "trial" all-steel monocoque/chassis progresses, I wanted to consider the materials that should be used for construction of the component parts of my final version. Jaguar themselves went through a similar exercise in 1964 when the XJ13 had reached an advanced design stage.

Before then, in the few years leading up to 1964, various studies/reports were made on things such as the shape of the overall body, the design of the underlying chassis structure and suspension design. One, quite advanced, design was for a rather more integrated monocoque design as shown in the following sketch from the November of 1963:

Early monocoque design for the XJ13.
© Image - reproduced with permission.

However, the above design was not progressed further and, instead, a separate monocoque/chassis unit was developed which was to be clothed by a largely unstressed outer skin:

Representation of original XJ13 monocoque/chassis.

In essence, the final design for the monocoque/chassis consisted of three main elements:

sills/floor/front & rear bulkheads
front suspension structure (coloured yellow)
rear engine mounting and rollbar (coloured green)

The design of the front suspension went through a few different incarnations as the car was being assembled. Derrick White, Jaguar's talented Race-car Engineer argued for a cutting-edge design (for the time) using widely-spaced upper and lower wishbones. This would have given better handling and a greater possibility of maximising the benefit of the wider tyre widths which were increasingly being used in the mid-1960s. His persistent arguments were repeatedly blocked by Bill Heynes who favoured a more tried-and tested production-based suspension. Heynes eventually prevailed and a design, based on the 1964 Lightweight E-Type was adopted - albeit with coil-over shocks in place of torsion bars.

This decision was one of the things that led to Derrick White becoming increasingly frustrated and his eventual defection to Cooper - a great loss to Jaguar. White went on to design the GP-winning Cooper-Maserati of 1966. Heynes, at the time, had been given direct supervision of the XJ13 project and it has been argued that his enormous workload at the time contributed to the slow development of the XJ13. Fortunately, Mike Kimberley was eventually given day-to-day responsibility for the car and development then continued at a greater pace.

Meanwhile, in 1964 when the car had reached an advanced design stage - on paper at least - Jaguar conducted an investigation into the best materials of construction for the chassis/monocoque. They considered mild-steel, aluminium and titanium. The investigation concluded:

" ... For a given rigidity the weights of chassis built from 22swg mild steel, 14swg aluminium, and 18swg titanium would weigh almost exactly the same.
Chassis constructed to the same design from 22swg mild steel, 14swg aluminium and 18swg titanium would have safety factors (based on ultimate tensile stress) of 1.00, 1.43 and 1.71 respectively (relative to 22swg mild steel)
In view of the difficulty of working and welding titanium and its cost, and because it shows no weight advantage for a given rigidity, it appears that the choice must be between mild steel and aluminium ..."

In the end, the chassis sections coloured yellow/green in the drawing above were fabricated from mild-steel. The main centre section was fabricated from aluminium.

According to Peter Wilson, who actually lent a hand in constructing the XJ13:

" ... the monocoque was constructed almost entirely from NS4 2 percent magnesium and 2 percent manganese, half-hard alloy sheet, mostly of 18 swg thickness (0.048 inches), together with some sheet steel pressings in areas of high and concentrated stress, such as the main engine mountings and front suspension attachment areas."

The modern equivalent, Aluminium 5251 (NS4), is available and will be used for the recreation along with steel pressings where appropriate. I must admit to some relief that Jaguar didn't choose titanium

For those engineers amongst you, and those well-versed in the mysteries of things such as Young's Modulus (I certainly don't include myself here!), the following summarises some of the data presented in Jaguar's investigation into material choice:

MATERIAL	GAUGE	THICKNESS in	WT/SQ FT	YOUNG'S MODULUS (E.psi)	EXT vs STEEL	SAFETY FACTOR vs STEEL
Mild Steel (UTS=30T/sq in)	24	.022	0.896	30 x 10⁶	1.27	0.78
	22	.028	1.141		1.00	1.00
	20	.036	1.467		0.78	1.28
	18	.048	1.956		0.58	1.71
Aluminium (NSA half-hard; UTS = 15T/sq in)	22	.028	0.380	10 x 10⁶	2.90	0.50
	20	.036	0.502		2.26	0.64
	18	.048	0.669		1.68	0.85
	16	.069	0.892		1.27	1.14
	14	.080	1.115		1.01	1.43
Titanium (UTS = 30T/sq in)	22	.028	0.655	16 x 10⁶	1.81	1.00
	20	.036	0.840		1.41	1.28
	18	.048	1.120		1.05	1.71

As is well-known, there is no such thing as a chassis that doesn't flex, but some are much stiffer than others. The choice of material is critical in this respect. The range of chassis stiffness has varied greatly over the years from about 500 lbft/degree in the 1930s to more than 20,000 lbft/deg in a modern race car. I should be able to measure the stiffness of my completed chassis and it will be interesting to compare the all-steel "trial" chassis to the final version.

Different chassis designs each have their own strengths and weaknesses. Every chassis is a compromise between weight, component size, complexity, vehicle intent, and ultimate cost. And even within a basic design method, strength and stiffness can vary significantly, depending on the details. There can be no such thing as the "ultimate chassis" for every car, because each car presents a different set of problems. The XJ13 chassis gave a whole new challenge because of the intention to mount the engine as a fully-stressed member - with the whole of the rear suspension hanging off the engine/transaxle. I believe this would have beaten Colin Chapman's Lotus by a few years had the XJ13 actually raced. Jaguar carried out a number of theoretical investigations into how well the car should stand up to the torsional loads applied to the chassis because of this arrangement and the final rear chassis design took these anticipated loads into account. The front suspension arrangement bears many similarities to the E-Types with steel tubing attached to the front bulkhead and Jaguar will have built up much experience of this design.

It may seem that an aluminium chassis was always the logical choice, but this is not necessarily true. Aluminium is more flexible than steel or titanium. Indeed, the ratio of stiffness to weight is almost identical to steel, so an aluminum chassis must weigh the same as a steel or titanium one to achieve the same stiffness. Aluminium has an advantage only where there are very thin sections where buckling is possible. This certainly applies to the large sill and floor sections.

In the end, the "unintended crash test" crash at MIRA in 1971 demonstrated better than anything else the soundness of Jaguar's basic chassis design. Although there was considerable damage to the outer structure, the basic chassis/monocoque survived almost intact. More importantly, the legendary Test Driver, Norman Dewis, survived unscathed.

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How many quad-cam V12s were built and where are they now?

Neville — Fri, 21 Oct 2011 17:01:00 +1000

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A question often asked of me is,

"How many prototype V12 quad-cam engines were built by Jaguar and where are they now?"

As I reported on this blog back in May 2010, the answer is SIX. Of this six, only three progressed beyond test-bed stage and were installed in cars. A seventh engine was assembled as a 60° V8 and run on Jaguar's test bed. The V12 block for this engine was converted into a V8 using a special crankshaft with throws for only eight of the twelve cylinders. There were plans to assemble an eighth engine but it never reached the test bed stage.

The above has now been confirmed by XJ13-expert Peter Wilson in an excerpt from his forthcoming book which appears in the November 2011 issue of "Jaguar World". I can now add further confirmation of these facts from a collection of previously unknown and unpublished original documentation. These documents were in the personal collection of the late Claude Baily - the architect of Jaguar's quad-cam V12, their legendary XK engine and quad-cam 90° 8 litre V8 amongst others.

Jaguar's Claude Baily.

Claude Baily joined the SS Jaguar drawing office during the second World War and his engineering talents were soon exploited by Jaguar. Baily became intimately involved in Jaguar's plans to replace their pre-war engine designs with a new generation of engines designed to power their latest saloons. He is perhaps best known for his part in the design of the legendary XK twin-cam engine.

Claud Baily's appointment letter.
© Copyright Tony Bailey (WPO Communications) - not to be reproduced without permission.

Spending long war-time nights fire-watching in a small office above the assembly tracks in Coventry, in the company of William Lyons, William Heynes and Walter Hassan, the architecture of the world-beating XK engine was laid down. The new engine was required to reliably provide a minimum of 160bhp, have a long service life and be refined in operation. Before the end of the war, a number of experimental single-cylinder and full engines were evaluated. The following original document from 1941 is likely to relate to one such experimental engine. J.A.Prestwich was better known by its initials "J.A.P." whose engines were used in many famous motorcycle marques and early aeroplanes. Customers included Morgan, Triumph, Brough Superior, AJS and HRD.

12th December 1941 - letter to SS Cars referring to experimental engine.
© Copyright image - not to be reproduced without permission.

4, 6, 8 and 12 cylinder configurations were all considered at this very early stage but it was the 4 and 6 cylinder versions that were finally adopted. It has to be said that the BMW 328 engine played an important part in formulating the architecture of these engines. Indeed, Heynes was great friends with an owner of a 328, Leslie Johnson, who loaned his 328 to SS Cars for evaluation. Johnson was a British racing driver who competed in rallies, hill climbs, sports car races and Grand Prix races. Johnson's car was highly developed and had raced pre-war. In my opinion, the styling of the XK120 owes much to the BMW. A BMW saloon was also acquired by SS during the war and was fitted with one of the early experimental engines (the "XG"). Walter Hassan used this car as his own personal transport for an extended period for evaluation. One of Jaguar's own 2.5 litre SS Saloons was also used for testing the prototype engines although most of the development work was carried out on the test bed.

3.5 litre experimental XK engine - drawing produced to calculate compression ration.
© Copyright image - not to be reproduced without permission.

Left to right - Walter Hassan, William Heynes, Claude Baily.
© Copyright image - not to be reproduced without permission.

Heynes and Baily applied all their thoughts on engine design to the XK engine although they later commissioned Henry "Harry" Weslake to help optimise their design. Jaguar already had a long association with Weslake, a cylinder head specialist who had been instrumental in modifying the side valve standard engine used in the first SS sports car. He also worked on the larger SS engine. It is believed he was involved in the design of every Jaguar engine up to and including the V12 of the early 1970s.

Harry Weslake - © Copyright image - not to be reproduced without permission.

The following Weslake report gives a fascinating insight into his evaluation methods and his closing summary bears testament to the soundness of the XK basic design. Weslake concludes:

".... The engine has stood up remarkably well through these series of tests. The valve gear has remained quiet throughout, there has been no sign of variation in oil pressure and the engine improves in power out-put the longer it runs. The tests have been very severe, particularly the distribution ones, but never once was any mechanical trouble experienced. It is suggested that some breather attachment should be developed in order to keep a small depression in the crankcase so that oil corrosion can be minimised and this would also help to stop oil leaks, particularly in the valve chest covers ..."

© Copyright image - not to be reproduced without permission.

The camshaft drive was by duplex roller chain - an arrangement that was carried forward to the quad-cam V12 prototype engines. This arrangement was used in the first engine installed in the XJ13 as well as the second engine built and tested in a Mk.10 Jaguar. The "genetics" of the XK engine could clearly be seen in the later quad-cam V12. The following page of sketches (made by Claude Baily around 1949/50) clearly show how he was formulating a suitable cam drive for a quad-cam engine. It is believed the sketches were produced as a precursor to designing and building a quad-cam 8-litre 90° V8 engine for a post-war military application. A similar architecture found its way into Baily's quad-cam V12.

Baily's drawings showing his ideas for a quad-cam duplex chain drive
© Copyright image - not to be reproduced without permission.

Claude Baily had been working on a quad-cam 60° since 1949/50 - perhaps earlier. By the February of 1951 a fully-working engine may have been running on the test bed. This 12-cylinder engine was later developed as an 8-cylinder variant for military use. The following quad-cam V12 performance data was recorded on the 19th February 1951.

Claud Baily's 1950/51 60° quad-cam 8-litre V12 engine performance data.
© Copyright image - not to be reproduced without permission.

The following picture shows Baily's data in his own hand. Was this an estimate/conjecture or are they figures actually recorded on the test bed?

Claud Baily's 1950/51 notes.
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In 1962, Baily was given the go-ahead to develop his design as a 5 litre V12 to challenge at Le Mans. Although primarily designed for racing, consideration was also given to using the engine in production cars. At least two years before the go-ahead, Baily's 60° V12 engine was being proposed as a future Jaguar engine with a range of possible capacities as the following memo from Claude Baily to William Heynes demonstrates:

5th December 1960 memo - "POSSIBLE FUTURE RANGE".
© Copyright image - not to be reproduced without permission.

The quad-cam V12 engine project was given the code "XJ6" - not to be confused with the saloon of the same name. "XJ6" followed on from "XJ5" which was the code name given to the Mk10 replacement (eventually to become the 420G). Two Mk.10 cars (XJ5/4 and XJ5/5) were to become mules for the production variant of the "XJ6" racing engine. The following memo confirms that six prototype engines were being developed.

25th November 1964 memo - "12 CYLINDER ENGINES".
© Copyright image - not to be reproduced without permission.

The first two engines (XJ6/1 & XJ6/2) were first assembled to almost identical specifications which included dry-sump lubrication and Lucas mechanical fuel injection. In April 1966 XJ6/1 was installed in the XJ13. The second engine, XJ6/2, was installed in a Mk10 Jaguar (XJ5/5 - manual gearbox) on 14th April 1965. It was converted to wet-sump lubrication although its Lucas fuel injection system remained. After six months of testing in the Mk.10, XJ6/2 was removed from the car and reunited with a dry sump for further test bed development. In March 1966 it's dry sump was again converted to enable fitment in a second Mk.10 (XJ5/4 - automatic gearbox). By this time it had acquired a sextet of SU carburettors. It ran for almost 35,000 miles in this car before it was removed and replaced in XJ5/5. It was finally removed from the latter car and placed on the test bed for further development/testing until it was put into store in March of 1969. It remained as a complete engine until I acquired it in 2010. It is now being rebuilt to its original specification and will be placed in my replica of the 1966 XJ13.

So, to answer the question "How many quad-cam V12s were built and where are they now?" SIX quad-cam V12 engines were built.

XJ6/1 The first quad-cam V12 built but only the second to leave the test-bed and be installed in a car (XJ4/1). Damaged in 1967 and retained as a spare by Jaguar.

XJ6/2 The second quad-cam V12 built and the first to be installed in a car (XJ5/5) Survived as a complete engine and sold by Jaguar in the mid 1970s. Currently under restoration to original specification (same build spec as XJ6/1).

XJ6/3 Only ever ran on the test bed in a variety of configurations. Has not survived.

XJ6/4 Built using cast iron block and ran on test bed. Has not survived.

XJ6/5 Internally modified to run as a V8. Ran on test bed for a short while in 1965. Surviving components are with a collector in the US.

XJ6/6 No records exist. It is believed this engine was never actually assembled.

XJ6/7 Built to trial a die-cast "open-deck" engine block. Installed in XJ4/1 (XJ13) to replace its original engine when damaged in 1967. Remains in the car to this day.

XJ6/8 Built to competition spec with ultimate development of cylinder heads but never left the test bed. Cannibalised whilst in storage in 1969. Cylinder heads placed on XJ6/2 which remain with it until today. The engine block found its way into an XJ13 replica built by Bryam Wingfield for the collector Walter Hill.

It is interesting to note that Jaguar's XJ13 currently has a die-cast block that differs from its original XJ6/1. This die-casting process is used to reduce costs and will have been more relevant for a production as opposed to competition engine. The following letter indicates the target casting weight of a V12 block (OXW 5620 is an experimental part number current at the time of quad-cam testing)

Die Casting Quote.
© Copyright image - not to be reproduced without permission.

The XJ13's rather poor power to weight ratio when compared with its likely Le Mans competitors may have contributed to this attempt to lighten its weight?

As Mike Kimberley recorded after a test of the XJ13 at Silverstone in 1967:

BHP per lb weight

Ferrari P4/ .210

Lola Chev/ .207

Ford Mk4/ .206

XJ13/ .177

It is also interesting to note that the engine currently installed in the XJ13 has a single OPUS 12 cylinder distributor. Its original engine, XJ6/1, as well as XJ6/2 were fitted with twin 6-cylinder distributors.

XJ6/2 Original twin distributors as originally fitted to XJ6/1.
© Neville Swales.

XJ13 single 12-cylinder distributor on XJ6/7 engine.
© Neville Swales.

The rebuilt XJ6/2 will, of course, be built using its original twin distributors. In 1966 Claude Baily was charged with pricing the OPUS system. The following letters give an interesting insight - comparing the various options under consideration.

© Copyright image - not to be reproduced without permission.

There are other differences between the XJ13's original engine (XJ6/1) and the one currently installed in the car (XJ6/7). One is the inlet manifold throttle bodies. The first photo shows the original (1967) arrangement with dual throttle bodies (and separate mounting plates - coloured yellow) and the second shows the current arrangement (photo taken 1973) with individual throttle bodies and a single mounting plate on each head. Note also the different cam cover treatment - the earlier engine has the "trademark" polished cam covers wheras the currently-installed engine has a crackle-black finish.

1967 (original car)
© Copyright image - not to be reproduced without permission.

1973 (rebuilt car)
© Copyright image - not to be reproduced without permission.

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Building the Chassis/Monocoque

Neville — Wed, 28 Sep 2011 00:04:00 +1000

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Background

Work has finally commenced on building up the chassis/monocoque of my recreation of the 1966 Jaguar XJ13 - a "snapshot" of the car as it was in 1966 before it was crashed and modified. Almost 18 months of painstaking and exhaustive research has revealed details of the original 1966 car which will hopefully allow us to recreate the car as Malcolm Sayer intended - without the later "1970's" modifications/enhancements.

Research is still ongoing and takes advantage of recent, previously-unpublished, documentary finds as well as details soon to be revealed in Peter Wilson's forthcoming book - the definitive story of the XJ13 and the quad-cam engine that powered it. Peter's book is scheduled for launch towards the end of November 2011. A tantalising glimpse is available on Paul Skilleter's website.

Peter Wilson book - "XJ13".

Piecing together details of the original car has been an exhaustive and a very time-consuming process. Originally centred around the relatively few original documents that have survived as part of Jaguar Heritage's archive, research was supplemented by face-to-face and written communication with surviving ex-Jaguar employees. Chief amongst these is Peter Wilson (Jaguar Competition Department 1961 - 1966). Since leaving Jaguar, he has worked in a number of prominent and senior positions in the automotive industry including time spent Brico Engineering, Cummins Diesel Engines and British Leyland. Since his retirement in 1999 he has written the definitive work on the Competitions Department between 1961 and 1966 including not only the XJ13, but a significant era in the racing and development of the E-Type. I can heartily recommend Peter's book "Cat Out of the Bag" which is available from Paul Skilleter books at www.paulskilleterbooks.co.uk. Others have included the Jaguar automotive electrician Bryan Martin who actually wired up the original car and applied all those "temporary" red dynatape stickers (which still "grace" the car almost 50 years later ...).

Another invaluable resource has been Norman Dewis himself - not only from his numerous recorded interviews and recollections but face-to-face discussions at Jaguar Heritage. I am the proud owner of a personally signed copy of Norman's autobiography "Norman Dewis - Developing the Legend" which contains some facts about the XJ13 - the whole book is a fascinating read.

Norman Dewis' Autobiography - "Developing the Legend".

The work of creating the car has been entrusted to North Devon Metalcraft - a long-established family-run company manufacturing high quality, complete steel and aluminium motor bodies and replacement panels. ND Metalcraft was founded over thirty years ago by the father of John and Paul Evans who run the company today. Their late father was a time-served craftsman with experience stretching back to the 1950's. As well as being a Freeman of the City of Coventry he handbuilt the first London Black Cab. He passed his skills on to his sons Paul and John and now ND Metalcraft are best known for their body/chassis work on the Shelby Cobra, Jaguar, Aston and Triumph TR. The quality of their work is beyond reproach and I am confident in their ability to deliver an absolutely authentic 1966 XJ13 copy.

North Devon Metalcraft.

North Devon Metalcraft - XJ13 monocoque buck in the company of an Aston and Triumph.

As I researched the original XJ13 it very soon became apparent that there is no such thing as an original XJ13 blueprint, construction plans or drawings. To make matters worse, Jaguar have never allowed anyone close enough to the XJ13 to take detailed measurements for the purposes of manufacturing a replica. Replica manufacturers who claim they have had privileged access to the XJ13 are not being truthful. Others who say they have copies of original manufacturing plans are telling lies. Testament to this are the number of inaccurate XJ13 replicas currently in existence - to be truthful, I have yet to see a replica that accurately replicates the current car - and I have seen lots in the last 18 months!

The detailed information needed to reconstruct the original 1966 XJ13 has had to be pieced together from original drawing fragments, original Malcolm Sayer 3D measurement data, period photographs and the surviving remains of the original car.

Very early photo of the 1966 XJ13 clearly showing original lines of front and rear wheelarches.

It has to be remembered that the car currently in the Jaguar Heritage Collection differs in many respects from the 1966 original. Although many components such as the engine, instruments, chassis/monocoque, bonnet lid etc survived the crash intact, it is unlikely that original components such as the windscreen would actually fit the rebuilt car's body and there are numerous differences in the body form - some subtle and others rather more substantial (such as later 1970's flared wheelarches and the overall length of the car).

Crashed XJ13.

However Jaguar's XJ13 does provide clues to be able to "peel back" changes made in 1972/73 and reveal many features of the original car. For example, evidence of where the crumpled remains of the original body was cut away from the monocoque and how the new body/outer-sills were attached can be seen in the following sequence of pictures:

The following original 1965/66 photograph (reproduced with permission) shows the original sill in place in the car. The TIG weld and breather(?) holes are highlighted in yellow.

Photo of original 1965/66 monocoque. (The more eagle-eyed of you may notice the dash panel instrument layout differs to that in the current rebuilt car as well as their E-Type origins).

A separate panel is riveted to the floorplan (highlighted below) and meets the folded-over sill along the TIG weld. I suspect this panel had to be separate because a row of rivets attaching it to the floorplan can clearly be seen when the car is viewed from underneath (it would not have been possible to place these rivets if the sill/floor was formed from a single sheet of aluminium and folded back over itself to meet the floor).

Photo of original 1965/66 monocoque.

The car suffered substantial damage to its sills during its crash in 1971. Indeed, Norman Dewis' account of the crash suggests a sill may have made contact with a sand-filled oil drum. The following photo of the rebuilt car gives evidence that the outer sill was replaced and joined to the upper sill cover at its outer edge. The join was masked by the door rubber sealing trim and was roughly pop-rivetted into place.

Sill detail - rebuilt car.

Use of 3D Reverse-Engineering

A major contributor to the project has, and continues to be, Stuart Brown of 3D Engineers. Without these cutting-edge reverse-engineering techniques, the ability to produce an absolutely authentic and accurate replica would have been severely compromised.

Stuart Brown scanning original quad-cam V12 engine.

What is 3D Engineering?

In simple terms, 3D scanning is a fast and supremely accurate method of putting physical measurements of an object onto the computer in an organised manner, resulting in what is commonly called 3D scan data. Typically, the 3D scan data is represented with a scale digital model or a 3D graphical rendering. Once the scan data is on the computer, all of the dimensions of the physical object can be taken, such as length, width, height, volume, feature size, feature location, surface area, etc. This even extends to being able to calculate things such as centre-of-gravity, suspension clearances, how well various components such as radiators etc will fit in the final car etc.

Components that are known to have been used in the original XJ13 can be scanned in this way and added to the 3D scan data. This includes things such as the windscreen (made using original tooling), E-Type rear light clusters and front suspension components.

In general, a device that captures 3D information from a physical object is referred to as a 3D scanner. There are many different methods for capturing the 3D measurements of a physical part and thus, many different types of scanners. Stuart himself makes use of various scanners including an OptiNum 3D optical scanner.

Stuart Brown of 3D Engineers trying his hand at wheeling an aluminium panel under the watchful eye of John Evans of ND Metalcraft. The verdict was that "Stuart should stick to what he is best at - 3D Engineering ...

Because the 1966 XJ13 doesn't exist in its original form it has been necessary to supplement the digital scan data with data from other sources. Even if Jaguar made the rebuilt XJ13 available to us for scanning (unlikely in the extreme!)it would be of little value to us because it differs from the original 1966 car. One of the major sources of this 3D data for the 1966 XJ13 are documents containing measurements made in 3D space originally by Jaguar - possibly Malcolm Sayer himself. As Peter Wilson describes in his book "Cat Out of the Bag", Bob Blake built the original XJ13 by starting with a baseboard marked out with 10" squares. Malcolm Sayer's design was translated into 3D measurements by recording various points in 3D space relative to the baseboard markings. For example, the left-hand steering rack inner ball joint was defined as being 24.330" from the zero line on the baseboard, 17.320" perpendicularly up from this and 14.740" from the baseboad centreline.

Location of left-hand steering rack inner ball joint in 3D space.

I have obtained a large number of original key measurements such as this which precisely identify the location of key components such as front and rear suspension, monocoque/chassis dimensions etc. All of these critical measurements have been incorporated into Stuart's digital representation of the car.

The first task is to recreate the 1966 monocoque chassis - as was the case when Bob Blake picked up his first piece of aluminium and pondered Malcolm Sayer's measurements in 1965. The following picture shows the original XJ13 monocoque in the process of construction in 1965/66. If you look very closely at the bottom right of the picture it is possible to make out the 10" x 10" squares drawn on the baseboard.

Original 1966 XJ13 - chassis/monocoque construction detail - reproduced with permission.

This second picture is a representation of what the finished monocoque/chassis will look like.

Representation of original XJ13 monocoque/chassis.

We decided to produce two major buck/formers for our recreation - one for the chassis/monocoque and a second for the body itself. The following pictures show a digital representation of the chassis/monocoque buck followed by its full-size version. The central section and bulkheads are removable and will be replaced by the body buck when the chassis/monocoque is complete and we are ready to start work on the body. The plan is to first build a basic monocoque using sheet steel before committing ourselves to a full monocoque built using original-specification aluminium. I plan building a total of two full aluminium monocoques.

According to Peter Wilson,

The modern equivalent, Aluminium 5251 (NS4), is available and will be used for the recreation along with steel pressings where appropriate. This attention to detail will extend to the choice of aviation-quality rivets as original (I have seen too many oversize rivets used in replicas!)

Chassis/Monocoque - digital image.

Chassis/Monocoque buck.

The XJ13 used E-Type front suspension using coil-over shocks in place of torsion bars, vented discs and specially-manufactured calipers. All of these components will be used with modifications as per original.

Paul (ND Metalcraft) identifying data points on bulkhead from original Jaguar XJ13 data.

The front of the sills/floor. A "trial monocoque" being constructed using sheet steel. Once we are happy with the details we shall work using the rather more expensive original-spec sheet aluminium. I shall end up with a complete surplus steel monocoque before we begin building the final aluminium version. I don't know what I shall do with it yet - any offers/suggestions?

Rear view. The cross-hatched section will be removed. Note the width of the sills - seems I will have to lose some weight to fit in! The original cockpit is rather cramped (as is the cockpit of the rebuilt car).

"Trial" Chassis/Monocoque - side view.

To be continued ...

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Why didn't the XJ13 race?

Neville — Sat, 25 Jun 2011 01:54:00 +1000

The XJ13 first ran in April 1966 and, by the summer of 1967, development was still continuing apace with an extended test at Silverstone in August of that year. This was the ninth test carried out over a period of less than six months which does demonstrate Jaguar's commitment to the project at that time. These tests were carried out with the full knowledge of Jaguar's senior management with test reports widely distributed internally by the project leader - Mike Kimberley.

Michael J. Kimberley (“Mike”) C.Eng., F.I. Mech. E., F.R.S.A., F.I.E.D, F.I.M.I has had a remarkable career in the motor industry over the last 56 years, working with some of the great engineers, innovators and leaders of the worlds motor companies. Mike started as an apprentice with Jaguar in 1953 before rapidly progressing to becoming in Section Leader, Special Projects at Jaguar in 1965 where he lead the team developing the Jaguar XJ13 Le Mans car, under such famous names as Jaguar founder Sir William Lyons and Jaguar race director Frank (Lofty) England ...."

Mike Kimberley - Jaguar XJ13 Project Leader.

During this active development phase it seems that most of the testing was carried out by David Hobbs with additional drives by Richard Attwood and Norman Dewis.

It was David Hobbs who set the closed course record (167.5 MPH) for UK with the XJ13. This record lasted for 19 years. Hobbs' first race was in 1959 driving his mother's Morris Oxford. He turned professional in 1964 and raced extensively world wide for 30 years. His last race driven was the Masters Championship in 1993.

David Hobbs - racing driver and former Jaguar apprentice. Picture taken at the 2009 Motorsports Hall of Fame Induction.

Richard Attwood was born in Wolverhampton, Staffordshire. Richard James David "Dickie" Attwood (born 4 April 1940, Wolverhampton, Staffordshire) is a British former motor racing driver. During his career he raced for the BRM, Lotus and Cooper Formula One teams. In his whole F1 career he achieved one podium and scored a total of 11 championship points. He was also a successful sports car racing driver and won the 1970 24 Hours of Le Mans race, driving a Porsche 917.

Richard Attwood - racing driver and former Jaguar apprentice.

Norman Dewis is Jaguar's legendary Test Driver. Dewis is best remembered for a career spanning 33 years at Jaguar. In the words of Paul Skilleter,

" ... He tested and developed a remarkable series of cars, rode with Stirling Moss in a C-type in the 1952 Mille Miglia, drove a 190mph works D-type in the highly dramatic 1955 Le Mans, raced in the Goodwood 9 Hours, and set an amazing 173mph production car record at Jabbeke in Belgium with an XK 120. Completing over a million test miles at 100mph-plus average, Norman also played a crucial role developing the revolutionary Dunlop disc brake, and survived high-speed crashes and rollovers in the days before seat-belts – and without ever breaking a single bone ...."

Norman Dewis - Jaguar's legendary test driver.

A quick search of the internet will uncover the commonly-held view that it was an impending change to Le Mans engine capacity regulations alone which led Jaguar senior management to halt further development of the car. However, the truth is perhaps a little more involved than this and it seems a number of factors may have conspired to halt further development of the XJ13.

An impending change to the Le Mans regulations to limit engine capacity to 3 litres. In Lofty England's own words, in a memo to William Heynes, he stated "... the 3-litre maximum engine capacity formula for Group 6 prototype cars will be applied to all sports car championship races, which includes Le Mans, for the next three years, i.e. up to and including 1970, which period coincides with the remaining period of the current Formula 1 racing car regulations ..."
The spectre of the "GT40 Armada" in 1967. In the spring of 1963, Ford heard that Enzo Ferrari was interested in selling his company to Ford. Ford committed millions of dollars researching and auditing Ferrari's company only to have Ferrari unilaterally withdraw from talks at a late stage. This angered Henry Ford II who directed his racing division to find a company that could help them build a Ferrari-beater on the world endurance-racing circuit. The Ferrari-beater turned out to be the Mark IV GT40 which, although american-built, was based on a collaboration between Ford and England's Lola. Ford did not, at this time, have the racing prowess to take on the likes of Ferrari so had earlier engaged in discussions with England's Lotus, Cooper and Lola - eventually choosing the latter as a partner.
The BMC takeover of Jaguar. On 11 July 1966, the "merger" of Jaguar with the British Motor Corporation was announced. In reality, this was a takeover by BMC of Jaguar, but Sir William Lyons maintained control of most of his his empire. One reason that Lyons agreed to the 'merger' was to get financial backing for future model programmes. Lyons saw Jaguar's future success lay in introducing new road cars. Jaguar's finances were stretched at the time and racing had reached a new level of professionalism and expenditure that Lyons could not now justify.

On the 29th September 1967, Lofty England said:

" ... we are about to commit ourselves for considerable expenditure with ZF for the supply of special gearbox units for the current XJ.13 5-litre competition car and also a 3-litre version, which is a new project ...."

The fact that Jaguar were actively considering a 3 litre version of the XJ13 indicates it wasn't this rule change alone that would have prevented them racing. England's other comments in the same memo give an indication of the real reason development of the XJ13 was shelved:

" .... there does not, therefore, appear to be any point in doing any further development work on the 5 litre car or, in fact, on a 3-litre version, unless it is our intention to produce a lightweight 3-litre Formula 1 type engine, as cars which will be competing in sports car championship races will in effect be Formula 1 racing cars with bodywork to meet the sports car regulations ...."

In other words, reading between the lines, not only would development of a competitive car be very expensive, it would also have to compete against the equivalent of then-current Formula 1 cars. It would have seemed very unlikely that Jaguar could have triumphed under those circumstances. Finances, since the BMC takeover, were tight and Lyons' emphasis would have been on new production models - not racing - especially not where Jaguar would stand little chance of winning.

The decision was made - late in 1967 - to stop active development of the XJ13 and emphasis switched to a V12 engine for the future lineup of road cars.

It is interesting to see what might have been if a 3-litre version of the XJ13 had been developed. Would it have been along the lines of one of Malcolm Sayer's drawings from around that time?

3 litre successor to the XJ13?

Prototype V12 - Rebuild Specification - Cam Drive

Neville — Wed, 22 Jun 2011 16:01:00 +1000

The time has come to consider the specification for the rebuild of the quad-cam V12 engine. The first important thing to consider was the means of driving the four camshafts.

As stated previously on this blog, the intention is to recreate an EXACT copy of the XJ13 as it was in its heyday in 1966/67 - WITHOUT its subsequent modifications which include its "delightful" 1970s-style flared wheelarches, alloy wheels and gear-drive to the cams. Contrary to common belief, gear-driven cams were not installed in the car until 1978 - a good 11 years after the project had been allowed to die. The XJ13 NEVER ran with gear drive to the cams in period - the cams were always driven by duplex chains. My original engine has duplex chain drive to the cams - as was the case with both engines originally installed in the XJ13.

This "gear-driven cam" myth became widespread by the publication of cutaway drawings such as the ones shown below. Indeed, Jaguar themselves began to believe their own myth.

Cutaway drawing of engine fitted to XJ13 in 1978.

Detail of partial gear drive to cams - part chain and part gears.

The confirmation that the XJ13 never ran with gear-driven cams in period can be found in Jaguar's own archive. The archive contains a series of engine test logs - a log for each of the six prototype engines assembled as quad-cam V12s. Of these six original engines, only three survived as complete units(although a fourth was subsequently built up from new and used parts left over at the end of the project and used by Bryan Wingfield in a XJ13 copy for the late Walter Hill). Two of the three engines remained with the XJ13 and I have the third. As well as these engine logs, a number of original reports and other documents have survived. The facts recorded in these documents can be used to accurately chart the progress of these engines. A good 45 years have elapsed since the project commenced and people's recollections of events all those years ago may be a little hazy - even those who were directly involved at the time. It is for this reason that I base my conclusions purely on the documentary evidence.

The logs confirm the XJ13 never ran with gear-driven cams in period as follows:

Only two of the six prototype engines have ever been installed in the XJ13. These are recorded as "No.1" and No.7".
The first engine to be installed in the XJ13 was "No.1". This unit was NOT built to competition spec and did NOT have geared cam drive.
After a spell of testing on the test-bed (conducted by Mr J Eastick) "No.1" was installed in the car in April 1966 - " ... engine handed to Mr Brookes for installation in XJ13 rear engined car..."
In the meantime, "No.7" engine was being developed on the test bed. This engine - No.7 - HAD been assembled with gear-drive to the cams. " ... 12/8/65 ... built to competition specification ...". Later that year, in December while the engine was still on the test bed, the timing gear on "No.7" engine was replaced by the timing gear from the "No.4" engine. " ... timing chain brackets, chains, sprockets, dampers from No.4 ...". "No.4" engine was the only V12 engine with a cast-iron block (the other engines were all alloy). "No.4" was not built to competition specification and had duplex chain drive to its cams. "No.4" may have been subsequently smashed up and has not survived.
For the remainder of 1966 and the start of 1967, the XJ13 continued its development powered by the chain-driven "No.1" engine. Meanwhile, "No.7"'s development continued on Jaguar's test bed with numerous references to the cam chain drive in its testing log.
On the 23rd April 1967 disaster struck! Norman Dewis missed a gear change at MIRA whilst testing - " ... unable to test for extended period. Dewis missed gear. Suspect bent valves ..." The XJ13's engine ("No.1") suffered extensive damage after the missed gear change. The "No.7" engine, still with chain-driven cams, was hurriedly prepared for installation in the car. On the 10th May 1967 "No.7" was removed from the test bed - still with chain-driven cams. Installation of "No.7" in the XJ13 commenced on 11th May 1967. "No.7" was recorded as still being in the car as late as July 1973 " ... engine in car for Silverstone demonstration run on 14/7/73 ...".
Meanwhile, "No.1" was returned to the test bed for further development/testing where it remained until 1978. In July of 1967, gear-driven cams were added to "No.1" while it was still on the test bed.
During this time, my engine, "No.2" continued to be developed both on the road and on the test bed. Indeed, it remained under development long after the other V12s had been removed/dismantled for storage. Development of "No.2" continued until 1969 when it was used to carry out comparisons with the road-car single overhead cam engine. It has the distinction of being the very first Jaguar V12 ever to run on the road and may have been the only engine to have reached the 502bhp @ 7500rpm falsely claimed for the engines installed in the XJ13. It is likely the maximum power developed by engines fitted to the XJ13 was a much lower 438bhp.
In 1978 disaster struck again ... " ... 3/7/78 (No.7) removed from XJ13 car after damage to 'A' bank cylinder head during warm-up for demonstration run at Daily Express March meeting. Engine known to have over-revved during missed gear change, would appear to be broken tappets or tappet guides, No.6 exhaust valve head broken off and jammed in seat ...". It was at this point, as late as 1978, the XJ13 was fitted with gear-driven cams for the first time - long after the project was dead, after its crash and after it had been "modified" for a life of demonstration runs only.

"No.1" engine remains with the XJ13 to this day.

Prototype V12 - Part 4 - Stripdown

Neville — Sun, 27 Feb 2011 20:10:00 +1000

In January of 2011, on a very cold January morning, the restoration of my quad-cam V12 began in earnest with a total stripdown and detailed examination. The task of rebuilding this important engine has been entrusted to David Butcher.

David can draw on his vast experience gained from many years of rebuilding Jaguar engines from the 1960s to date. He has had a long involvement with Jaguar engines since his days working alongside the late Ron Beaty at Forward Engineering. Although in "semi-retirement", David's skills are very much in demand today - particularly by racers and enthusiasts. David has worked on all variants of Jaguar's classic engines including the Group C and prototype Le Mans racers.

David Butcher starting work on the prototype V12.

We were privileged to be joined at the initial engine stripdown by Peter Wilson and Jim Eastick. Both Peter and Jim worked at Jaguar on projects associated with the XJ13 - Peter on the car itself and Jim on the prototype's V12 engines.

From left to right - Peter Wilson, David Butcher and Jim Eastick.

I was fascinated to learn from Jim Eastick that my engine has a direct connection with the legendary Ron Beaty as it was Ron who actually ran and optimised my engine on the Jaguar test bed. Beaty joined Jaguar and made his way up to being one of the all time greats at the works. He worked in the former competition dept and was experimental engineer for the V12. In the late 1960's Ron Beaty formed the company Forward Engineering which made him a household name in the Jaguar world, creating power units for British and world water speed records, Lister Jaguars (Beaty created the original Lister XJS with Brian Lister) as well as many track records both here and abroad. The original TWR XJS's were also "Forward " powered as were many small volume constructors like Panther. David Butcher worked alongside Ron Beaty at Forward Engineering and played an important role in some of Forward Engineering's various projects. Other notable "Forward Engineering Graduates" were Rob Beere and Carl Taylor of Rob Beere Racing.

While David worked on the engine, I was treated to an accompanying dialogue of recollections of life at Jaguar at the time of the project between Peter, David and Jim - memories sparked by details of the engine revealed as the stripdown progressed - recollections not only of the engine itself but also the many individuals involved at the time. Sadly many of these individuals are no longer with us. Jim also brought with him his personal notebook containing notes made while the prototype engines were actually being run on Jaguar's Test Beds - a book he kept very close to his chest!

Jim Eastick consulting notes made during prototype engine testing.

My engine was the second engine assembled and is believed to be one of only three engines surviving having left Jaguar as a complete engine. Two of the three engines remain with the XJ13. There is a fourth engine which was assembled from a collection of new and used parts left over at the end of the project and installed in a replica for the late collector Walter Hill by Bryan Wingfield. As the stripdown progressed it soon became clear that the engine was not only complete internally but was in quite remarkable condition despite its 40+ years of storage.

Head removal.

Jaguar's habit of liberally applying "Wellseal" to gasket surfaces was very much in evidence! Having removed the heads, the condition of the bores and pistons became apparent. Although there is slight surface oxidation on the crowns of the cast alloy pistons, this is to be expected on an engine that has been stored for this period of time. It does confirm that the engine has spent its last 40 years undercover and in dry conditions. The slight oxide buildup was only present on the pent-roof piston crowns and the remainder of the pistons was found to be in quite remarkably good and usable condition. The lack of any significant carbon buildup does tie up with the original testing logs which indicate the engine was only run for a short time on Jaguar's test bed before being removed for storage in December of 1969. The final bout of testing was for emmision comparisons with the SOHC production engine.

The cylinder block is a L.M.8 sand casting and has a sump face on the crankshaft centre line. This is in contrast with the later SOHC V12 which had a much longer "skirt" which helped increase block stiffness. The prototype engine is a solid casting as opposed to the die-cast "open deck" design of the later engine. This makes it a rather heavy engine which is difficult to manouevre by hand - ask me how I know!

Cylinder heads showing "tin" gaskets. In the foreground can be seen the original twin distributors. Twin distributors were used in the original 1966 XJ13 and were only replaced with a single "modern" V12 distributor during the car's rebuild in 1972/73.

Hemispherical combustion chambers.

The V12 cylinder head design is very similar to the 6-cylinder XK engine in basics such as valve operation with a few significant differences. In an attempt to arrive at a more compact and efficient combustion chamber, the chamber depth was reduced to 1.03" (from the XK's 1.30") and the included valve angle was reduced.

As explained by Jim Eastick, the V12 prototype engine has equal firing impulses along each bank and can be carburetted as an in-line 6 cylinder. The bore and stroke is 87mm x 70mm giving a displacement of 4991cc.

All prototype engines were fitted with twin 6-cylinder distributors. One of the many changes made when Jaguar rebuilt the XJ13 after its crash in 1971 was their replacement by a single 12-cylinder distributor. One of the two distributors, the "master", contained two sets of contact-breakers plus a centrifugal advance mechanism that served both distributors. The second distributor, the "slave", was simply a distributor for the H.T. current. My engine will be rebuilt with both distributors as original.

Jim Eastick explaining how he had added extra springs to the "master" distributor in an attempt to reduce points bounce during testing.

The heads on my engine are numbered 18 and 19. This confirms them as the ultimate development of the prototype cylinder head having an optimum subtended angle of 41 degrees to the valve axis with camshaft centres raised by 0.25". The cylinder heads remaining with the XJ13 may have never achieved the widely-reported maximum power of 502 bhp at 7,600 rpm achieved by an engine with this design of head.

The following picture shows the modified sump fitted to my engine. Although it is the engine's original racing dry sump, it was considerably modified in period to enable its fitment in the two Mk10 Jaguar "mules" for testing. The original gear scavenge/pressure in-sump gear pump was found to be in place but modified so that drive was transferred to a rear "wet-sump" pickup. The welded-up position of the original scavenge/pressure outlets can be seen at the front of the sump. The plan is to return the original sump to dry-sump specification.

Modified dry sump.

The four studs on the skirt of the block are used to not only mount the engine but also to provide a location for the rear trailing arms. There will be a corresponding pair of locating studs on the final sump. The engine/transaxle in the XJ13 supports the entire rear suspension.

Seen here is part of the duplex chain cam-drive arrangement - incidentally, as originally fitted to the XJ13 engines and not gear-drive as widely thought.

Chain-drive to cams.

The next few pictures show the sump being removed - revealing components not seen since the engine was assembled in Coventry in the late 1960s.

Preparing to remove the sump under the watchful eye of Jim Eastick.

Sump removed revealing combined scavenge/pressure pump and shaft used to transfer drive to the rear oil pickup. As with the later SOHC engines, a steel plate extends the full length of the crank.

Oil pump detail.

Chain drive to oil pump.

The engine has seven 3" diameter main bearings which means the later shells can be used (perhaps with slight modification to oil-holes). The big ends are unique which may cause some problems in finding replacements. When Jaguar recently rebuilt the XJ13's engine they found it necessary to increase the diameter of the conrod big ends to accept "off-the-shelf" bearing shells. This avoided a cost of something in excess of £20,000 to tool up for the prototype's unique bearing size. However, we have yet to fully explore whether or not the original size shells can be found. The crank pins are 2.187" diameter and are 1.20" wide to accept the side-by-side conrods. The conrods are offset 0.75" bank-to-bank. The crankshaft is made from forged steel and is lubricated using an end-to-end feed from grooves in the main bearings. The same sludge trap system as used on the earlier 6-cylinder XK engine was used with transverse oil feed holes. Although we have yet to confirm whether or not the crank was nitrided it is known that Jaguar used a EN 40 nitrided crankshaft in the competition V12.

David then began to remove the timing-chain cover so that pistons and crank could be removed.

Preparing to remove timing cover.

Timing cover removed.

The following picture shows detail of the lower two chains (four separate chains in total). One chain drives the oil pump while a second takes drive to intermediate sprockets - one for each head. Another sprocket is used to drive the twin distributors and Lucas fuel injection metering unit via a "Jackshaft". A hydraulic chain tensioner can be seen towards the bottom of the picture. The two top chains (driving the cams) are tensioned by an external nut applying pressure to a slipper.

The complexity of this chain layout was a factor in deciding to go with a SOHC layout for the production engine. The weight and cost could be reduced using a single chain drive with four sprockets compared to the prototype's four chains and twelve sprockets. Also, the noise level of the quad-cam layout was unacceptably high for a production engine. However, for racing purposes the quad-cam layout was preferred.

Timing chain detail.

Drive removed from oil pump.

Steel cover plate and scavenge/pressure pump removed.

Referring to original notes .....

Oil pump.

Removing slave distributor drive.

Distributor drive "jackshaft"

Piston sees light of day after 40 years.

All bearing shells were in remarkably good condition - confirming the engine's short time on Jaguar's test bed before the engine was removed for storage.

Journals also in good condition.

"Yours Truly" lends a hand.

Connecting rod still polished and shiny after all these years.

Preparing to remove crankshaft.

Jim Eastick remembering modifications to oiling system.

Detail showing "grooves" around oil holes on alternate big ends.

Slip-fit dry liners.

Crankshaft removed. Bearing shells were all in excellent condition.

Now that the engine has been stripped it can be given a detailed examination/measurement in readiness for its rebuild. As a matter of course things such as valve springs and (probably) valves will be replaced. After standing for more than 40 years it makes sense to replace items such as this - the thought of a detached valve in the rebuilt engine doesn't bear thinking about! Fortunately, we are well-blessed in the UK with skills and expertise to be able to build an engine such as this.

To be continued ...