AC Cobra
USA/UK
The A.C. Cobra is at present an export only model. It is based very closely on the A.C. Ace, which normally carries a Bristol or Ford Zephyr engine. Suitably strengthened to withstand an American Ford V8 unit of 4t litres capacity, the Cobra is manufactured at the A.C. factory at Thames Ditton and shipped to the States, where car and engine meet. About 10 Cobras per week are sent over to Shelby American, Inc., who are selling them like hot cakes.
The A.C. chassis was designed by John Tojeiro, and was in fact based on the very successful Bristol-engined "Toj" raced by Cliff Davis. It has a laddertype tubular frame, with independent suspension at both ends by transverse springs and wishbones. The Cobra has tubes of heavier gauge and the shorter Vee-type engine has permitted the insertion of extra cross-bracing. Rack and pinion steering and anti-roll torsion bars front and rear are additions to the specification, and naturally the differential and universally jointed half-shafts are heavier. The differential is of the selflocking variety and the track has been slightly increased, both front ann rear.
Panelled in aluminium, the open two seater body has a lower grille and bonnet than that which the overall height of the Bristol engine demands. The Ford unit, with its own all-synchromesh four-speed gearbox, is in fact notably compact. With the over-square dimensions of 101.6 mm. x 72.9 mm. (4,727 c.c.), it probably develops around 275 b.h.p. in touring trim and over 350 b.h.p. when tuned for racing. All this in a car weighing some 18 cwt. can only result in a simply shattering performance.
I was thus more than delighted when, during some glass-lifting exercises at the Steering Wheel, Carroll Shelby suggested that I should borrow his personal Cobra for a day. To make the most of the occasion, that day started before 5 a.m.! Carroll had remarked that the car was "set up for the street", which means that it was neither geared for an ultimate maximum speed nor fitted with the greatest available number of carburetters. It was, in fact, far more flexible on top gear than any luxury limousine and its traffic manners were impeccable.
What can one do with a car which will out-accelerate practically anything on the road when top gear is engaged at 15 m.p.h., yet has about the best close-ratio gearbox that could be imagined? The desire to feel that "whoosh" of power from zero revs. on fop is always competing with the excitement of rushing past 50 m.p.h. on bottom gear. With the final drive ratio fitted to the test car, 6,500 r.p.m. came up at once in top and I lifted my foot. This resulted in a timed speed of 136 m.p.h., bur of course 150 m.p.h. could be exceeded with a suitable crown wheel and pinion in place.
The engine must be praised very highly indeed. A new lightweight Ford model, it is utterly smooth at all speeds up to 6,500 r.p.m., and would certainly go. much higher if one turned a blind eye to the dial. The clutch copes happily with the mammoth torque and the four synchronized gears may be selected with the greatest ease and rapidity. The roads were damp, though not wet, when I started my performance tests, and rain was actually falling at their completion. As a result, the figures which I recorded could be beaten on a dry road. Nevertheless, to accelerate from a standstill to 50 m. p.h. in 3.8 seconds or to 80 m.p.h. in 8.2 seconds is a somewhat dramatic performance.
Very quiet mechanically, the power. unit has just a trace of exhaust "beat". This noise, so typical of big V8s, is rather objectionable to most hearers and could probably be eliminated by some cross connection of the two separate exhaust branches. It would appear that V8 noises are accepted in America, but in England they are no more popular than were the single-cylinder detonations of the 500 c.c. racers. This is a minor point, however.
The A.C. chassis has been improved by the adoption of rack and pinion
steering, which is both sensitive and
precise in action. The angle of roll
during fast cornering has also been greatly reduced by the front and rear
torsion bars. At fast touring speeds,
the Cobra is easy to handle and the
sheer luxury of having all that power in reserve is one of motoring's greatest
sensual pleasures.
Driven to the limit, the Cobra is not
for the beginner. To start with, it is a
foot shorter in the wheelbase than other cars of comparable potency, such as the
Ferrari, so one tends to be rather busy
when drifting fast curves on full throttle.
I admit that my test was too short to
allow me to get to know the car, and I
am sure that I would have gained confi dcnce with experience. The machine is
being improved with the rapidity which
results from racing a new model, and I
expect that it will become easier to
handle in spite of its spectacular performance. In any case, it is only when'
driven at racing speeds that the Cobra demands considerable skill.
The traction afforded by the independent rear suspension, plus the self
locking differential, renders extremely
rapid starts particularly easy to carry
out. The disc brakes on all four wheels
are immune from fading, but demand quite a lot of pedal pressure for emergency stops at fairly low speeds. Continuous use of the brakes from high
speeds causes them no distress whatsoever, which is a comfort when so much performance 'is available.
Well-made and attractively finished,
the aluminium body is of that excellence for which A.C.s are renowned. The
hood does not flap, though it naturally bulges a little at over 120 m.p.h.
American instruments were fitted to the test car with proper round faces, but
the speedometer was inoperative so 1
'calibrated the rev. counter, which was
notably steady. I found the seating position very comfortable and the ride was
good over all but the worst bumps.
The A.C. Cobra is a high-quality
sports car with a stupendous performance. It is outstandingly flexible and
has perfect town manners, while it may
be driven everywhere on top gear or
run at high speeds on the close "indirect ratios, according to the whim of the
moment. It is by no means heavy on
. petrol and its great reserve of power,
' when sensibly used, must be regarded as
an excellent safety feature on crowded roads.
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CARROLL SHELBY (1925-)
A smooth-talking Texanchicken farmer and race driver, Shelby was responsible for the :wild AC Cobra and Shelby Mustang. A firm believer that there was
no substitute for cubic inches, he was a seminal figure in the Sixties' American muscle car movement.Author: ArchitectPage
