simply stated, The AC Cobra attained higher performance figures than any
other production automobile we have tested. and it did it with the
Carroll Shelby chose a chassis that
has figured largely in hybrid projects for some time, and with great
success. Coupling the stout AC chassis and lightweight AC body with a
souped-up Ford engine, Shelby came up with an extremely track-worthy
sports car of very high performance indeed.
introduced the Tojeiro design as the AC Ace in 1954, powered by the
ancient long-stroke six-cylinder overhead-valve two-litre. In 1956 AC made
a deal with Bristol to use the famous BMW-derived Bristol power plant, and
the AC-Bristol became a respected competitor in sports-car racing. The
next engine option was the 2.6-liter Ford Zephyr engine, introduced in
1961, and then there was the Cobra.....
test report from the USA
a fourth-generation hybrid, the car must be considered in light of its
true purpose--SCCA class warfare. For such usage, it is accurately aimed,
and viewed in that light the secondary considerations such as street use
must necessarily come off second best.
for instance, presents some uncomfortable problems. With the Cobra's very
powerful engine developing maximum torque at 4,800 rpm, its high gearing,
and its fierce clutch, every stop and start presents an interesting
challenge in turning noise into motion. Its poor steering lock makes
parking and manoeuvring highly complicated. And finally, the battery does
not get enough input current to cope with low-rpm running under normal
conditions, let alone when using the heater, headlights, wipers, and the
inadequate electrical fan mounted in front of the tilted radiator.
Ford of Providence. Rhode Island, which supplied the test car, suggested a
smaller generator pulley to cure the constant discharge problem. A better
solution might be the alternator, since it is already optional for the
260-cubic-inch Ford V-8 that is used in both Fairlanes and Galaxies.
the car presents problems in traffic, one would assume that they would be
dissolved by the open road--the opener and the more like a race course the
better. In fact, the effortless sort of cruising that the car's
performance would seem to promise is considerably handicapped by the
encroachment on passenger space that the big V-8 makes. The engine is set
back in the chassis enough so that the driver's acceleration foot gets
cramped after awhile in the only possible position (with the right leg
bent inwards, toward the other, at the knee). Some relief is afforded by
the long pedal travel of the throttle control, but it only comes with
variations in speed.
the credit side, in regard to the driver's creature comforts, is an
interesting refinement in the clutch and brake pedals. These are hinged
below floor level, and also at the pedal faces. As a result, the pedal
faces maintain a constant total contact with the sole of the driver's shoe
regardless of the depression angle. The pedals are set closely enough
together to allow room for the left foot beside the clutch.
simplicity is the term that first comes to mind for describing the Ac
chassis (designed by John Tojeiro for his own sports-racing car in 1952
and subsequently taken over by AC). The frame consists of two
large-diameter steel tubes with heavy cross-members front, centre, and
rear. Narrow-diameter tubes are to support the all-aluminium body. All
wheels are independently suspended by means of lower wishbones and upper
transverse leaf springs. The result is a chassis that has given away
nothing, as far as handling goes, in production-class racing since its
Tojeiro also designed the body, a sleek shape reminiscent of the Ferrari
166 Mille Miglia.
work on Ford's Challenger V-8 engine began in 1958 under the leadership of
Robert F. Stirrat. Weight reduction became a main objective during this
period, and Ford aimed at producing a cast-iron engine that could compare
in weight with an aluminium power unit of similar displacement. The
decision to use cast iron was based on such advantages as the graphite
content in its matrix, which serves as a lubricant in itself and also
attracts and holds minute particles of engine lubricant, thus further
reducing engine wear. Cast iron also has excellent sound-damping
qualities, and tends to damp vibrations. Thermal expansion characteristics
are nearly ideal, assuring proper clearances at all operating
by Ford Foundry's latest techniques in thin-wall casting, with extensive
use of resin-bounded cores, Stirrat came up with an engine that weighed
only 450 pounds complete.
dimensions are very compact--8.93 inches high, 16.36 inches wide, and
20.84 inches long. A study of the short and stiff five-bearing crankshaft
indicated that about 70% of the total unbalanced couple could be balanced
by means of normal crankshaft counterweights. Two external counterweights
provide the other 30%, one mounted in front of the timing sprocket and the
other as an element of the flywheel. No vibration damper was needed.
Crankshaft stiffness is such that the fourth harmonic occurs beyond the
normal engine operating range.
modifications include higher compression, a hotter camshaft and a
four-barrel carburettor (Ford or Holley). As a power option, four Weber
carburettors will be available, an din racing tune the engine puts out 355
cars are shipped complete, except for engine and transmission, from AC,
and engines and transmission are shipped from Ford to its dealers whom
Shelby has authorized to carry out the installation. Our test car had the
lesser state of tune (and had not been test-driven by Carroll Shelby).
Even with the mild engine, the torque characteristics were incompatible
with most street driving, with a flat spot below 2,000 rpm and a really
devastating noise at maximum torque. We suspect that the valve clearances
were off on the test car, not only because of the terrific clatter but
also because the engine seemed to peak out before the 7,000-7,200 rpm that
Shelby claims to get with ease.
our acceleration tests, upshifts were made below 6,000 rpm, as no
improvement could be seen by staying longer in the lower gears. The
gearbox was not fully run in on the test car, and its movements were
inclined to be stiff. The short lever and its precise gate could be just
perfect, though, after another 5,000 miles or so.
has every other American high-performance car of recent times, Ford uses a
Warner all-synchromesh transmission. The gear ratios are very well chosen,
and close enough for racing, but it is a question whether a five-speed
unit would not give better results. With the 3.5-to-one final drive, a
starting gear is needed, and with a higher ratio, the car would be
undergeared for many circuits. Perhaps next year will see further
experiments in this direction.
in a chassis with less of a racing tradition, the power of the V-8 Ford
would have been an embarrassment rather than an advantage. The centre of
gravity is located slightly towards the rear, and the rear wheels have a
negative camber of about 3 degrees in their neutral position, with just a
trace of toe-in. This setup is obviously made to reduce or annihilate
oversteer.......but it is still the tail that begins to swing wide when
the limit is approached. Correction of such slippage is easy enough, with
judicious use of power.
existence of an actual limit of adhesion on a dry smooth surface seems to
be a purely hypothetical question with the wide-section flat-profile
Goodyear Blue Streak tires. Michelin X tires have always been an inherent
part of the AC Ace design and if the Blue Streaks fitted to the Cobra are
superior on a dry track, they certainly are not in the wet, on ice and
snow, or on a rough or irregular surface.
the many advantages of independent rear suspension, the one that stands
out on the Cobra is the unloading of the rear drive shafts and the
resultant lack of wheelspin, in spite of the lack of a limited-slip
for the comfort, the independent rear suspension makes absolutely no
contribution, since the springing is so stiff and wheel travel so
restricted. The whole car feels like so much unsprung weight at low
speeds, and it does not begin to soften up until about 50 mph. At racing
speeds it is highly satisfactory, each wheel staying on the ground and no
more than one deflection per bump being permitted by the hard springs and
the efficient shock absorbers.
ride gives the driver great confidence and help improve his feel of the
forces acting on the car, with the result that after a few hours at the
wheel at high speeds he begins to feel like an integral part of the
machine. Few modern sports cars can really give this impression--but then
the AC Cobra is not so much a modern sports car as a traditional sports
car brought up to the minute.
this feeling is obtained more in spite of than because of the driving
position. We were a little disappointed in the seats, which do not have
enough backrest rake (and only fore-and-aft adjustment of the whole seat).
The upright seating position is all right on a twisty circuit with plenty
of arm-and footwork, but far from ideal on a fast course with sweeping
top-gear bends. Since the steering is quite heavy at low speeds, turning
the wheel is easier when it is located at less than arm's length. At
speed, however, the steering becomes lighter, and as wheel movements are
ultra-small, with 1 2/3 turns lock to lock, most drivers would certainly
prefer a more reclining position with almost straight arms.
shocks are felt in the wheel, but with such direct and ultra-sensitive
steering, wheel movements are kept small and bumps could never alter the
course of the car to any extent. Road feel is excellent, and corrections
can be made almost before they become necessary.
stability at speed is usually good, regardless of crosswinds and road
surfaces. The car can be controlled with a fingertip on a good road, and
gentle curves call for, no extra force. Under racing conditions, a
reduction of steering-wheel work can be achieved by throttle steering, but
even on a normal road it pays to look ahead, and with intelligent driving,
it is possible to reduce the physical effort considerably.
when using the brakes on a slippery surface is imperative. the 12-inch
disks have no power booster, but so little pedal effort is required that
under extreme conditions most drivers are likely to apply too much force
on the pedal rather than not enough. The ultimate stopping power on a dry
surface is limited by locking of the rear wheels. The hand-brake is well
placed and comfortable in use, but it is not of the fly-off type as on
going the whole hog, HRG-fashion, the AC Cobra has a well-equipped
instrument panel, with gauges to tell you the temperature of the oil as
well as the water, large dials for MPH and RPM, and an oil pressure
gauge--but why the clock? It is obscured by the driver's right fist most
of the time, and when a clock is needed, it would hardly be considered
reliable enough anyhow.
is a roomy (relatively) glove box, but we were surprised to find there's
no map-reading light.
soft tops usually sacrifice a lot on the altar of lightness, and that of
the AC Cobra is no exception. It is not flimsy, and the fastening is
clever, but there is continual buffeting, rattles from the side windows,
drafts and leaks everywhere. In addition to the side clips at the
windshield edges, there is a slide at the center of the top of the
windshield frame, with the nailheads on the top securely fastened. The
frame for the top is removable and may be stored separately in the trunk.
time we test a genuine 150-mph road car, the question crops up whether
there is really adequate justification for their existence. In every case
we have been convinced that there is. For people who enjoy travelling
fast, the tremendous importance as a safety factor of a generous power
reserve at all times cannot be overestimated. High-speed highway merges
becomes routine and overtaking distances becomes amazingly short, so if
not used, the 150-mph sports car can be the safest yet simultaneously the
fastest (it goes without saying) car on the road.
AC Cobra is not as sophisticated or as well-integrated as the cars it is
competing with both in price and in racing classification. It will be
interesting to see if the phenomenal performance bias will "bring the car
off" as a commercial success. Commercial or not, the haircurling level of
performance the Cobra provides will certainly give the ranks of big
production-car racers pensive moments.