| The XK120 that was unveiled at the London Motor
Show in 1948 was the sports car that had everything: a roadster body
more beautiful than anything even Jaguar had produced before; an immensely
strong chassis that had taken years to develop; and an engine so sophisticated
that it looked as though it should have graced a Grand Prix racer
rather than a sports car costing only £998! This was not only
the first pure-bred Jaguar engine, it was also the world's first mass-production
engine with twin overhead camshafts and hemispherical combustion chambers.
Such technical sophistication had only been seen before in racing
cars costing a great deal of money and produced only in very small
quantities. Lyons, who was the inspiration behind the engine, gambled
once more on its staying in production for so long that the tooling
and development costs would amount to only a tiny sum on each engine,
But even he could not have guessed that the XK unit would be so successful
that it would still be powering Jaguars into the 1980s!
When this unit was still in the design stage during the war-time
fire- watching sessions, even engineers as experienced and adventurous
as Heynes, Hassan, Baily and Harry Mundy doubted whether it would
be possible to produce a twin overhead camshaft engine for a passenger
car. They recognized the advantages of such a layout in that it
produced tremendous power, but pointed out that it carried penalties:
these engines tended to be very noisy because long chains or trains
of gears were needed to drive the camshafts; they were difficult
to make, which inevitably meant that they cost more, and were potentially
less reliable; and they were far from easy to service. But Lyons
would not settle for second best and insisted that he must have
a 'twin cam'; what is more, it also had to look good! Once they
had expressed their reservations, Heynes, Hassan, Baily and Mundy
worked with a will that resulted in the sensational six-cylinder
in-line XK unit that produced no less than 160 bhp from 3442 cc.
They had the assistance of Harry Weslake, who was to help extract
even more power from the engine as time went on. With bores of 83
mm, the XK engine had a relatively long stroke of 106 mm, which
gave it impressive torque. Its crankshaft ran in seven main bearings;
this meant that the bottom of the engine was extremely strong, which
it had to be to transmit the power produced by the top end. The
cylinder block was cast in iron by Leyland Motors-the British truck
firm that would much later figure prominently in Jaguar history-and
the head made from alloy, which saved weight and dispersed heat
more efficiently. At first the engine was produced in a relatively
mild form of tune because it was feared that, had a more radical
stage of tune been adopted by using higher-lift cams, inexperienced
mechanics might damage the vital valve gear during the decarbonization
process, so common in those days. However, the quality of fuel improved
and 'decoking' became a relative rarity, and it was found that the
average mechanic was so proud to work on such a magnificent engine
that he did not 'mess it up', In any case, the XK engine's 160 bhp
was enough to propel the 1320 kg (2912Ib) car at more than 190 km/h
( 120 mph), hence the designation XK120.
A rather 'graunchy', but very reliable Moss four-speed manual gearbox
was used in a shortened version of the Mark V saloon's ladder-design
chassis. This used conventional half-elliptic leaf-spring rear suspension
with a live axle, and Heynes's new independent front suspension,
which employed wishbones and torsion bars parallel to the chassis
sides. A feature of this front suspension was the brilliantly simple
ball joints used to locate the stub axle carriers. Steering was
a recirculating-ball type and so arranged that it could be set on
either the right-or the left-hand side to cater for export markets
from the start.
The XK120 in production
At first the XK120 had an aluminium two-seater roadster body, built
in the old manner on an ash frame because Lyons did not envisage
making many of these cars. He saw them principally as a mobile test
bed for the engine and an advertisement for his planned Mark VII
saloon, which would use the same unit in the longer Mark V chassis.
The great expense of assembling the giant presses and tools needed
for all-steel body construction could be justified only if a large
number of cars was to be produced. As it happened, there was such
a demand for the car that he had to do just that, although it took
until 1950 to tool up for the first all- steel XK120. The demand
had been set off, first, by the car's spectacular appearance and
incredibly low price-there is some evidence that Lyons initially
saw it as a loss leader-and, secondly, by a demonstration for the
doubting Thomases that it really was capable of the performance
claimed when test driver 'Soapy' Sutton managed 213.4 km/h (132.6
mph) with a mildly modified version before astonished journalists
on the Jabbeke motorway in Belgium in May 1949. Only a V12 Ferrari
costing four times as much and available only to selected racing
teams could match this. So Jaguar, who had planned to spend the
year making Mark Vs and preparing for production of the Mark VII,
found itself with a bulging order book for XK120s.
Competition successes for the XK120
The first customer cars-mostly for export-left Foleshill in July
1949, a month before three were entered in the new Silverstone Production
Car Race. It was Britain's first big motor race since the war in
which production cars could be compared, and two of the XKs, driven
by Leslie Johnson and Peter Walker, left the field standing. Johnson,
who won at Silverstone, went on to perform impressively in America
before receiving a new works-supported XK120 in company with Walker,
Wisdom, veteran Italian racing driver Clemente Biondetti, and rallyman
lan Appleyard, whose successes with an SS100 included a Coupe des
Alpes in the Alpine Rally. Appleyard had special connections with
the factory because, apart from being a Jaguar dealer, his crew
consisted of his wife, Pat, who happened to be Lyons's daughter!
And their car, registered NUB 120, was to become one of the most
successful competition Jaguars.
Johnson spearheaded Jaguar's assault on the classic Le Mans 24-hour
race in 1950 and took his near-standard car up to third place, leaving
many outright racing sports cars trailing, until failing brakes
led to an overstrained clutch and eventual retirement. Many similar
cars suffered from brake trouble in those days because of the development
of all- enveloping coachwork. These bodies, which were better streamlined
than the old-fashioned types used on models such as the SS100, meant
that cars were capable of higher speeds, The result was that the
drum brakes suffered badly at the limit of their performance, as
they had to stop the cars from far higher speeds and, because of
the better streamlining, without the benefit of such a good flow
of cooling air. This problem was made worse by a reduction in wheel
sizes to take modern tyres, which meant that brake drums of smaller
diameter had to be used to fit inside the wheels, It was a problem
that was not really solved until the introduction of disc brakes,
pioneered on competition Jaguars. Despite the retirement of Johnson's
XK120 in the all-important Le Mans race, enthusiasts everywhere
were extremely impressed by its showing against far more specialized
machinery that could not be bought by ordinary people. And Heynes
was convinced that, with a special competition version of the XK120,
it would be possible to win at Le Mans. Lyons agreed and authorized
the building of the C (for Competition) type, which went on in 1951
to the first of Jaguar's five victories at Le Mans, and is described
in the 'Glory Years’ chapter.
Meanwhile XK120s continued to win races all over the world and
make up most of the fields in international rallies. By far the
most successful XK120 rally drivers were the Appleyards with NUB
120, which they used to win the Alpine Rally (1950, 1951, 1952)
and the Tulip Rally (1951) and many others in a life that extended
to more than 100,000 miles!
In America, world champion-to-be PhiI Hill bored out an XK120's
cylinder block to 3.8 litres (which was to become a significant
capacity in Jaguar history) and won numerous events; in Britain,
the greatest driver never to win a world championship, Stirling
Moss, made his name in the big time with one of the semi-works XK120s.
Moss was offered the car in 1950 when Wisdom opted for an official
works drive in a Jowett Jupiter in Britain's premier road race,
the Tourist Trophy, held on Ulster's Dundrod circuit. Moss overtook
Johnson to win in atrocious conditions and so impressed Lyons that
he was signed to drive for Jaguar when the company ran a full works
team of C types the following year. It was an excellent birthday
present for Moss: he was to be 21 next day! He also made mincemeat
of the opposition with an XK120 in the 1951 Silverstone Production
Car Race.
Other drivers enjoyed notable success with XK120s, particularly
the Belgians Jacques Ickx (whose son became a Grand Prix star) and
Johnny Claes who won the 1951 Liege-Rome-Liege rally-in reality
the world's roughest road race; former Spitfire pilot Duncan Hamilton;
and Sir James Scott-Douglas, who helped start the glorious Scottish
team, the Ecurie Ecosse.
The XK120 fixed-head coupe
As these stalwarts raced on their alloy-bodied XK120s, steel-bodied
cars, which weighed about 25 kg (56Ib) more, but looked almost exactly
the same, had been in production since April 1950. Production of
the Mark VII saloon finally started in October 1950, leaving Jaguar's
staff free to work on a fixed-head version of the XK120, which was
introduced in March 1951. It met the demand for a car as civilized
as the Mark VII saloon without sacrificing the performance of the
sports car. This new coupe was like an XK120 roadster (to use the
American description which has now become universal; Jaguar preferred
to call it a super sports) with an attractive steel top, the lines
of which bore a close resemblance to those of the Mark VII. Wind-up
windows replaced the roadster's sidescreens, the doors were fitted
with exterior handles and the interior upholstered like the saloon,
rather than the far more spartan-but lighter-roadster. Ventilation
had received special attention, with quarter lights front and rear,
following complaints about too much heat in the cockpit from people
using the cars in hot climates. A heater was also fitted as standard
following complaints from people living in cold climates about too
little heat in the cockpit! Wire wheels-like those used on an increasing
number of competition XK120s to assist brake cooling and fast wheel
changing-were offered as an option. When these wheels were fitted
to either the roadster or the fixed-head coupe, the rear spats had
to be left off because of the protruding knock-off hub spinners.
Soon after, Jaguar provided more options in the form of tuning
equipment for customers who wanted to use their XK120s (and Mark
VIIs) in competition. These consisted chiefly of higher-lift camshafts,
higher compression pistons, larger carburettors, stiffer springs
and thicker brake pads; they were based on well-tried items used
on the C type. These modifications could boost the engine's power
to 190 bhp.
Demand for the XK120 and the Mark VII was so great that Jaguar
was again faced with the old problem: the factory was not big enough.
So Lyons started searching for new premises once more and managed
to acquire a modern factory used by Daimler to make cars and buses.
Daimler had made armoured cars there during the war, but its needs
were contracting and in 1951 the firm decided to centralize its
operation on the main works at Radford, Coventry. Jaguar was happy
to move into the million square feet at Browns Lane, Allesley, on
the outskirts of Coventry, which is still the company's home.
Meanwhile, the fixed-head coupe, which was not normally used in
top--line racing because it was heavier than the roadster-although
it found favour in winter rallies-was publicized in 1952 by a run
at the Montlhery track near Paris during which Johnson, Moss, Jack
Fairman and Bert Hadley averaged 161.43 km/h (100.31 mph) for seven
days and nights to cover 27, I 19 kilometres (16,851 miles) and
take nine international records.
The XKI20 drophead coupe
The company was still recovering from the move to Browns Lane and
it was not until April 1953 that a new Jaguar was launched-in this
case a drop head coupe version of the XK120. This was more like
the fixed-head car than the roadster, with a well-tailored folding
hood replacing the steel roof. The roadster retained its spartan
trim and the V-shaped windscreen that protected its occupants so
well from the elements, whether the skimpy lightweight hood was
up or stowed away: it was considered normal in those days to drive
a roadster with the hood off in almost any weather.
The drophead coupe, however, was intended to be driven with the
hood down only when the weather was really good. This was particularly
important because the flatter, fixed-head style windscreen needed
with the wind-up windows set up air currents that whipped around
the back of the occupants' necks: fine on a good day but not so
pleasant on a bad one!
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