period test report from the USA

As 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.

Traffic, 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.

Tasca 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.

If 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.

On 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.

Classic 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 introduction.

John Tojeiro also designed the body, a sleek shape reminiscent of the Ferrari 166 Mille Miglia.

Design 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 temperatures.

Aided 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.

Its 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.

Shelby 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 bhp.

The 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.

During 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.

As 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.

Placed 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.

The 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.

Among 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 differential.

As 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.

This 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.

And 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.

Road 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.

Directional 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.

Caution 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 Ace-Bristols.

Without 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.

There is a roomy (relatively) glove box, but we were surprised to find there's no map-reading light.

English 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.

Every 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.

The 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.