The Jaguar Mark VII really was the car that was meant to power the new Jaguar Cars out from the shadow of the Second World War. Post 1945 England was in a fairly tight position and exports were to mean everything for manufacturers such as the relatively newly formed Jaguar Cars.

The Jaguar Mark VII was to be the modern post war design from William Lyons and was to be launched at the 1948 British Motor Show however like many development projects it did not run to time. Whilst the marvellous XK engine, designed during the war, was ready as was a new chassis to underpin the new saloon, the complex bodyshell required to finish off the project had run into major problems. The body had been subcontracted to Pressed Steel and the new design was running effectively 2 years late due to the sheer size of the panelwork and the required press tooling.

Thus the lead up to the 1948 Motor Show was, for Jaguar, a bit of a strange affair. Development had by then produced a great new engine in the form of the XK straight 6 cylinder, and a new chassis that was to be the foundation for their new saloon car, but no actual finished car!

With limited time Jaguar produced 2 new bodyshells and modified a MK VII chassis. The cars they then went on to show at the 1948 British Motor Show were the Jaguar Mk V saloon and the awesome XK120.

The Jaguar Mk V was definitely pre-war in design terms. It had the 3485cc "Standard" derived, six cylinder engine, which had already proved itself in the earlier Mk IV models but had a distinctly new chassis with hydraulic brakes and torsion bar front suspension. The Jaguar XK120 had a modified Jaguar Mk VII chassis and a new sports car body but with the fabulous new XK engine and wasn’t meant to be anything other than a showcase for the power unit. Neither car was the car that Williams Lyons had been planning to showcase.

The car that was to be the Jaguar Mk VII did not make is presence until the 1950 British Motor Show by which time the production of the bodyshell had been resolved.

It was worth the wait, and was to be the epitome of Jaguar’s slogan; “Grace,..Space… and Pace”.

The Jaguar Mk VII was a truly great car. It left behind the pre-war designs of SS Cars Ltd whilst providing the engine, chassis and running gear for the XK range of sports cars. This mechanical structure for the XK120 was to lead directly onto the C-type and D-type racers which were to provide Jaguar Cars with their glory years and probably the greatest decade in the company’s history.

But back to the Jaguar Mk VII, it is hard to put into words just how important it was for Jaguar Cars to have got the design for the Mk VII right. With hindsight this design was to place Jaguar on the world stage as a manufacturer and race car company with the obvious benefits to car sales.

For the Mark 7, Jaguar designed a modern and streamlined-looking steel body, featuring fully integrated headlights and mudguards, along with an increased rear overhang which gave the car enhanced presence. Removable spats enclosed the rear wheels. The steel sliding sunroof was a standard fitting. The windscreen was a two-piece item, becoming one-piece in later models. The car’s bulk, at 6ft 1in wide and 16ft 5in long, was diminished by the fine proportions and overall elegance of the body’s styling.

The interior could accommodate 6 if a bench front seat was specified. It amply qualified for the “acres of wood and leather” euphemism. Walnut veneer, Wilton carpeting and wool headlining imparted a luxurious aura. The front doors contained tool kits with a range of tools for routine maintenance.

It was with this high-performance luxury saloon project in mind that the famous XK engine was conceived and designed. Lyons called for an engine which was powerful, with ample low-speed torque, and with smoothness throughout the rev range. It also had to look good. The resulting engine was ready by the end of 1947 but, as the saloon for which it was intended was not ready, its first actual appearance was in the XK 120 sports car which was unveiled in 1948, two years before the Mk 7. In its early form the 3.4 litre engine developed 160bhp and 195lb/ft of torque, these figure rising with later models. This engine certainly fulfilled Lyon’s requirements. It was impressive both in power and in looks. Its twin-cam layout, polished aluminium cam covers and twin carburettors looked like something out of a grand prix car. The XK engine is one of the all-time greats. Its long production run and its ability to accommodate capacity and power increases have proved the soundness and strength of its original design.

The Mk 7’s transmission consisted of a Moss 4-speed gearbox with a Salisbury 4.27:1 axle differential. Wheels were 16in diameter with 5in wide rims, shod with 6.70 x 16 high-speed cross-ply tyres.

Braking was by 12in drums all round with self-adjusting twin trailing shoes at the front.

For the first time on a Jaguar, vacuum servo assistance was provided. Automatic transmission was offered in 1953 for overseas buyers, and overdrive the following year.

The Mk VII as a package was hard to beat. A spacious saloon with a great chassis, a sports car engine and a luxurious interior; what more could the Jaguar customer want? The Jaguar Mk VII was large in most respects but extremely stylish and set the standard for many years.

The Jaguar Mk 7M 1954-56

By the time of the 1954 upgrade, some 20,908 Mk 7’s had been produced. Jaguar presented the Mark 7M (“M” for “modified”) at the 1954 Motor Show. The modifications stemmed from experience in competition. During the early and mid-50’s the big Jaguars were successful in both saloon car racing and in rallying.

Stiffer torsion bars and half-inch wider wheel rims were fitted. The engine was of the same size and had the same 8:1 compression ratio, but now the power output was 190 bhp, thanks to larger valves and a higher-lift cam. The standard transmission remained a four-speed manual gearbox, but now with closer ratios. Overdrive was offered as an option. Additionally, the three-speed Borg Warner automatic, introduced in 1953 but hitherto available only on exported cars, became an option for British buyers.

The Mk 7M could be distinguished most easily from its predecessor by the 'horn grills' beneath the headlights. These replaced the auxiliary lamps which were now perched on the bumpers, slightly further from the centre of the car than hitherto. The bumpers now wrapped a little further around the corners of the car.

Following on from the Jaguar Mk VII the Mk VII and Mk IX really were much the same car externally but with upgrades to engine, transmissions and brakes.

The Jaguar Mk 8

The interior fittings were more luxurious than those of the Mk 7. Distinguishing visually between the models is facilitated by changes to the front grill, larger rear lamps and a chrome trim strip below the waistline which allowed the factory to offer a variety of two-tone paint schemes. In addition the new car had rear spats that were cut back to display more of the rear wheels. A one-piece windscreen replaced the Mk 7’s two pieces of flat glass. The interior now featured picnic tables which folded down from the back of the front seat.

The Mk 8 inherited the 3.4L XK engine from the Mk 7, sharing it with the Jaguar XK150 which appeared the same year. Mk 8 engine output was increased to 210 bhp by the fitment of the more efficient “B-type” cylinder head and a twin exhaust system. The claimed top speed, approaching 110 mph, was considered impressive for such a bulky car.

A variant, the Mk 8B which featured a glass division, was produced for government use.

The Jaguar Mk 9

After a two-year run of 2267 units the Mk 8 was replaced by the Mk 9. For the Mk 9 the engine was enlarged to 3.8L by increasing the bore size. Power increased to 220bhp.

Four-wheel servo-assisted Dunlop disk brakes and re-circulating ball power steering were now standard equipment.

The body was generally similar to its predecessor and the interior was in the same luxurious mode with extensive use of leather, walnut wood trim and deep pile carpet. A range of single and duo-tone colours was offered.

A car with automatic transmission tested by the The Motor in 1958 had a top speed of 114.4 mph (184.1 km/h) and could accelerate from 0-60 mph (97 km/h) in 11.3 seconds. A fuel consumption of 15.2 miles per imperial gallon was recorded. The car cost £2162 incl taxes of £761. In 1961 the Mk 9 was superceded by the completely new Mark 10 saloon.

Through the fifties Jaguar sold almost 50,000 of these graceful sporting saloons

Competition History

The Mk 7 was rallied successfully, although not as often as the more obvious choice, the XK120. However, on the occasions it did appear, it acquitted itself well with several class wins and placements during the early 1950’s. Highlights were the outright win in the 1954 MCC Round Britain Rally, and the outright win in the 1956 Monte Carlo.

The Mk7’s best-remembered competition highlights were in early touring car races, in particular the annual high-profile Daily Express-sponsored meetings at Silverstone in the 1950’s. The car won the race every year from 1952 – 1956, taking all 3 top places most years. It was also successful at club level during the 1950’s.

A Jaguar Mk 8 won its class in the 1958 Round Australia Rally which covered 10,500 miles. The same year another Mk 8 won its class in the Australian Economy Run.

By the time the Mk 8 came out however, the big car had been supplanted for competition use by the smaller and more nimble Mk1 saloon. The Mk 8 and Mk 9 therefore hardly ever featured in competition.

The Mk 7 became prominent again in club competition in 1975, the year in which the Classic Saloon Car Club inaugurated its race series for 1950’s saloons. As many as three Mk7’s appeared on the grid at each race during the early years of the series.

A fresh boost was given to its profile when The Goodwood Revival race meetings started in 1998. Up to four Mk 7’s, including Racing Green’s own car, featured in races during the early years. Our racing Mk 7 has appeared regularly at the Goodwood Revival, and at club races both in this country and abroad.

Our knowledge of how to prepare these cars for competition is based on the continuous development of our own successful car, and is unsurpassed.

Bodyshell

The Jaguar Mk VII bodyshell was a big step forwards from the pre-war designs. Gone were the running boards, separate front wings and headlights and here was a more modern saloon design. The fabrication of this bodyshell was to create the processes that Jaguar was to use for the next 20 years.

Despite the support of a strong pressed steel and welded chassis, the bodyshell was robustly constructed from heavy gauge steel pressed sections and was fully welded.

The steel bodies were built up from pressed steel panels with a large element of hand finishing and fettling to create the final required shape. The pressed steel work was not that accurate, certainly when compared to today’s standards, and there are a number of external seams to the bodyshell that had to be filled or disguised to create the finished vehicle. Lead loading was the conventional approach to resolving a variety of bodyshell issues on a steel bodied car but it is not without its own inherent problems. Nowadays there are high specification fillers which are probably the better option but it is clearly down to the individual’s choice when repairing these cars.

When the bare steel bodyshell was jigged and welded at the Jaguar factory all the relevant external seams were lead loaded which effectively means they were soldered over. This process requires the use of an acidic flux to clean the steel and the relevant area is then “tinned” whereby a layer of solder is attached to the steel surface. This process requires heating the steel to the melting point of the solder or tin and then building up the tin to the required thickness to effect the repair. Where the “tinning” process is correctly achieved all is well but elsewhere acidic flux can remain under or within the repair. Once the lead loading was complete the required shape was formed by wiping the hot solder or by filing and sanding the cooled material with obvious health implications given the constituents of the materials involved.

What this process means in practice is that there are complex, relatively poorly formed steel joints that have been intensively heated and coated with an acid based flux which is not necessarily fully cleaned. All in all a perfect place for rust to start and get a grip of such an impressive bodyshell.

The bodyshell is made up from relatively large sections of pressed steel so the lead loading is not a major element of the shape of the car. Jaguar Mk VII bodyshells were not given any level of rust protection apart from the external painting process so all the internal surfaces really were just waiting to rust away and only needed a damp climate to start this process. The cars had steel sunroofs as standard and this added a further degree of complexity to a restoration as well as allowing more water into the car!

The restoration of a Jaguar Mk VII body is not for the faint hearted as there is without doubt a lot of metal to work through. When looking at a Mk VII typical areas for corrosion are floor pans, sills, door skins, boot floor but there are cars available where virtually nothing is left of the body. The cars can rust badly as can the chassis. Rain can get into these cars relatively easily so do check for damp carpets and corrosion from the inside out.

The Mighty XK Engines

The famed 3.4 litre XK engine had been designed specifically for the new Jaguar Mk VII. However the XK120 had beaten the Mk VII to market and claimed this world class power unit nevertheless the XK engine was by rights designed and built for the Mk 7.

With the design commenced during the war years the 3.4 litre XK engine was to prove to be a great engine and to remain in production with Jaguar until the early 1990s. In the early ’50s this was the engine to have in your sports car, let alone a saloon such as the Mk 7, as it had just won at Le Mans which was about as high an accolade as was attainable. Imagine a similar situation today with a saloon car being offered by a major manufacturer with a Le Mans winning sports car engine under the bonnet!

The XK engine comprised of a cast iron block with alloy cylinder head with twin overhead camshafts operating 2 valves per cylinder in hemispherical combustion chambers. The crankshaft of EN16 steel was fitted with a Metalastic harmonic damper to remove damaging harmonic vibrations from the crankshaft. This design changed remarkably little over the next 40 plus years which really goes to show how good the original design and development process had been.

The power output of the 3.4 litre XK engine was gradually increased through the Mk 7 to Mk 8 era until for the Mk 9, Jaguar supplied the new 3.8 litre engine. The 3.8 litre version of the XK engine was only released in 1958, initially for the last of the XK150s and the Mark IX saloon.

These engines are still regularly raced and can be totally reliable if well looked after or rebuilt correctly. Really all that should be needed is regular servicing but careful attention should be taken of the antifreeze or coolant.

Overheating the XK engine can lead to a number of problems; typically blown head gasket or, more seriously, movement of the bucket guides in the head. This can be detected by a knocking noise from the camshaft area and generally on the exhaust side. This will require a cylinder head off rebuild and some machining operations to resolve. Low oil pressures tend to indicate a worn bottom end and will almost certainly lead to a full rebuild of the engine. Parts are all readily available.

Loss of coolant and subsequent low concentrations of antifreeze can lead to an accumulation of problems associated with the cooling system due to corrosion and build up of sludges and corrosion by-products. All XK cylinder heads were cast from RR50, an alloy developed by Rolls Royce during the war specifically for pistons for aircraft. This alloy was developed for high strength at high temperatures so is probably over specified for a cylinder head but one of its downsides is that it can suffer from significant corrosion to the water jacket. This can most easily be spotted at the interface with the cylinder head gasket where the waterways can corrode to the outside world in bad examples.

Internal corrosion to the blocks on Jaguars leads to underlying tendencies to overheat whenever the external temperature rise unduly, this is often put down to radiators, cooling fans etc but can remain as an unsolvable problem due to the fundamental nature of the corrosion.

Radiators, whilst they can become blocked and inefficient, are generally ok but again the problems always show themselves on hot days when the cooling system is pushed to its limits and struggling to keep core temperatures down.

There is no reason for XK engines to run hot providing they have been built correctly and have fully cleaned waterways.

PLEASE keep all Jaguars running on the correct levels of coolant. This is by far the best way to maintain the cooling systems and engines generally!!

Gearboxes

The Mk VII was fitted with the Moss gearbox and, given the engine was such a modern masterpiece for the period, the Moss gearbox harked back to previous times as it was effectively pre-war. Originally manufactured by The Moss Gear Company, one of Jaguar’s many suppliers, manufacture was taken over by Jaguar, and Moss seems to have disappeared by the late 1950s. The gearbox is a relatively simple 4 speed with no synchromesh on first or reverse. Reasonably strong in practise if a little agricultural it was to remain the standard equipment on these graceful saloons. The Borg Warner 3 speed automatic had been introduced in 1953 but only as an option for overseas purchasers, specifically the American market. This became an option for the UK market in 1954 and the overdrive option became available in the same year.

Clutches are again reliable, but, the original coil spring type clutch cover is a definite candidate for replacement by a diaphragm type as fitted to later Jaguars.

Front Suspension and Brakes

The Mk VII suspension was developed by Jaguar Cars specifically for the Mk VII but due to development problems also became the suspension for the XK120 sportscar and consequently the C-Type.

The front suspension on all these big saloons is virtually the same and is well designed and robust. The car is supported on torsion bars running parallel to the main chassis rails. Anchored onto the chassis under the footwells the torsion bars run forwards to the lower wishbones and effectively form the lower wishbone pivot. The chassis anchorage is fully adjustable and provides the facility to load the suspension, effectively setting the front ride height of the car.

The suspension arrangement is twin wishbone with an upright mounted on upper and lower balljoints. This design of front suspension was to remain with Jaguar for many years. All the components in the front suspension are easy and straightforward to maintain and simply need a regular grease to maintain in good condition as are all from the era when grease nipples were fitted to everything.

All these saloons, Mk VII-IX, relied on a steering box with a link bar running through the chassis box section. The manual steering box of the Mk VII moved on to power steering as standard on the Mk IX.

The steering boxes are reasonably well engineered but suffer from a number of faults. Racing Green offers an upgrade to the manual steering box replacing the inadequate ball bearings with tapered rollers and improving the feel tremendously in the process.

This range of mighty saloons spanned great changes to the braking systems as fitted to Jaguars. The Mk VII was supplied with drum brakes all round as was fitted to the original C-Type racers but by 1953 Jaguar had developed discs for these race cars. The Mk VIII was similarly braked. With the launch of the Mk IX in 1958, Jaguar moved to disc brakes all round on this road car. This was a major technological advance and whilst the Dunlop/Girling individual caliper piston units are dated by today’s standards they were a monumental leap forwards on the roads of the ’50s.

Given that these cars are not small or light by any standards, drum brakes are not really up to the requirements of current road use and on Mk VII and Mk VIII front brake calipers really should be considered as a required upgrade. Any spirited use of a standard Mk VII or Mk VIII will inevitably lead to brake fade or worse and drums on the front axle should be changed.

Rear Suspension and Brakes

The rear suspension is again relatively conventional and is a simple live axle located on leaf springs running front to rear. Location is not great and there are modifications such anti tramp bars to provide for a bit more positive positioning of the live axle.

Rear brake information really is the same as that given above for the front brakes.

Exhausts, Electrics and Fuel

Exhausts are relatively simple and should fit reasonably well as they literally run down the centre of the car. The only problem is likely to be in the region of the downpipes and their proximity to the “chassis” rails.

The fuel systems are generally fine as long as the filters are regularly replaced and tanks kept clean. The fuel tank is external to the boot so it is not unknown for the debris of years to mount up and corrode its way into the tank.

Electrics are all relatively straight forward and period but there is no real reason why it cannot be reliable if well maintained.

In General

Unfortunately water always seems to find a way into older cars especially given the UK climate! Over time this leads to great damage on a number of fronts and avoiding this degradation is very beneficial to the longevity of any car. Water tends to pool in the lower areas of the car ie footwells and carpets but as the temperature rises on warmer days this moisture evaporates and fills the car with high humidity air. As the day cools in the evening this moisture condenses on the colder horizontal surfaces of the inside of the vehicle such as the inside of the roof and boot panels etc. This condensate then runs off and into sections of the car where water could not normally access and can cause significant problems over time. Bodyshell, electrics, trim and interior finishes can all suffer with this continual degradation over time.

Ideally try to keep all classics in a dry environment with windows slightly open to allow the air to circulate and reduce the moisture levels in the car. Dehumidifiers are also very beneficial over the longer term.

Interior is relatively straight forward but water entry, as described above, to the cabin can lead to seat stitching rotting and to headlining and carpets suffering. Recently we received an E-Type coupe which had been unused for a year or so but moths had taken up residence and had done a surprising amount of damage. All those natural fibres had kept them well sustained!

The Jaguar Mk VII burst onto the scene in 1950 and was without doubt the aspirational saloon car of the period. Throughout the ’50s these big saloon cars were the cars to have and they are still sought after to this day albeit they do not have the same following as the XK sports cars or later compact saloons. Prices have been steadily climbing but, given their importance to the Jaguar name, are probably undervalued. Some minor upgrades to the earlier brakes, ignition systems and starter motors should prove sensible. Add a battery conditioner/charger to ensure easy starting in our brief summers and they are a joy on the road.

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