Hugely popular since its introduction in 1958, the Austin Healey Sprite (and MG Midget) over 110,000 had rolled off the prooduction line at Abingdon-on-Thames, helping to make the traditional home of M.G. cars the largest factory in the world, during the 1960's, devoted to the production of sports cars.
Around 85 per cent were exported, mainly to the United States, and it was to satisfy the demand from this market for more creature comforts and to bring the cars into line with the character of the MGB, that the M.G. Midget Mark II and Austin-Healey Sprite Mark III models were introduced.
There had been particular resistance to detachable widescreens in America, and the rising sales of rivals with wind-up side windows no doubt encouraged B.M.C. to incorporate this feature on their small sports cars. At the same time B.M.C. took the opportunity to rearrange the cockpit layout, not only making it more luxurious, but easier to "work" in.
Of course the true enthusiasts were only concerned with power output. There were cylinder head and exhaust manifold modifications, which increased maximum power to a genuine 59 b.h.p. (net) at 5,750 r.p.m., and a stiffer crankshaft was fitted to reduce vibrations.
Extra power from the engine was obtained by increasing the size of the inlet valves by 0·06in. and by modifying and reshaping the siamesed inlet tracts to reduce the "uvula" which separated the ports. At the same time, the compression ratio was raised to 9:1, although an 8·3:1 commpression ratio engine was available for countries with low octane petrol.
A new cast-iron, four-branch exhaust manifold, similar in shape to that of the MGB, was adopted to replace the older type inherited from the Austin A.35
. The modified manifold eliminated the double bend in the down pipe and was responsible for one of the extra horse-power. Crankshaft main journals were increased in size from 1·87in. to 2·0in., while a minor change saw the abandonnment of the engine driven petrol pump in favour of an S.U. electric unit.
The rear suspension was completely revised by the adoption of half-elliptic leaf springs. It had always been a problem to make quarter-elliptic springs of the old design with a combination of low rate and sufficient lateral rigidity to locate the back axle accurately. Moreover, the whole weight of the rear of the car was carried on an anchorage point only 4in. long, requiring long, heavy channel section stiffeners to spread the loads through to the struccture. The result was always a compromise resulting in a hard ride and undue roll stiffness at the rear, with a consequent tendency for the Sprite to be very sensitive on steering.
Eliminating The Quarter-Elliptic Parallelogram Layout
The new springs gave a better ride, and the previous iterations tendency to "dart" was eliminated without any loss of steering accuracy. The four-blade, half-elliptic springs were anchored at the forward ends in brackets, and at the rear were shackled to a plate bolted to the floor by way of the box section members which reinforced the boot floor. With this half-elliptic rear springing the unsprung weight of two heavy axle brackets needed for the former quarter-elliptic parallelogram layout was eliminated, plus half the weight of the radius arms and approximately one third of the weight of the thick, wide, quarter-elliptic spring. The engineers were also albe to eliminate much of the body stifffening required by the old layout.
Thus the total weight saving all but made up for the extra weight of the door glasses and window lifts, and the all-up weight of the Mark III cars is, amazingly, only 6lb more than that of its predecessor. The change to wind-up windows did not detract from the sporty appearance of the car, and only a die-hard enthusiast would have bemoaned the passing of detachable widescreens. To fit wind-up glasses into the relatively thin doors of the Sprite and Midget without a major body redesign called for curved side glasses. This also ensured adequate elbow room was retained withhout any increase in external body width.
Small swivelling quarter vents with non-locking catches were standard equipment and a new, more rigid windscreen frame with full height cast aluminum pillars was fined to provide a firm sealing abutment for the doors. A thin tie rod between the top and bottom rails of the screen frame prevented it "opening up" when the hood was tensioned and also provided a mounting for the driving mirror which was previously located on the scuttle, where it created a blind spot.
Inside The Cockpit
The main effect of the revised cockpit layout was to give it a designed look, rather than the appearance of having been assembled from a number of unrelated components. The revised facia was both good looking and practical, with the matching trip speedometer and electronic rev counter angled inwards to fall on the arc of focus of the driver's eyes. Both were clearly visible through the unobstructed upper half of the a new three-spoke spring steering wheel, which had a cowled column incorporating the indicator stalk.
The instrument panel was a steel pressing taking up two-thirds of the width of the facia, and on the left-hand section (right hand for left-hand-drive cars) the fuel gauge and a combined oil presssure gauge and coolant thermometer were mounted. This section of the panel also provided a mounting for the electrical switches, choke, and heater controls and screenwasher plunger. The whole of the panel and facia was finished in black crackle enamel, surmounted by a paddded leathercloth roll which was extended along the tops of the doors.
On the passenger side a crushable, fibreboard parcel shelf with a padded edge provided stowage for maps and small oddments, and was designed to collapse safely in the event of accident. The floor and transmission tunnel were covered in good quality pile carpet, and this had bound edges and rubber heel mats for both occupants.
On The Open Road
If you ever get the chance to sample the original Sprite, then a Mark III, you will quickly realise the difference between the two, particularly in the suspension area. In fact, such were the changes made that the Sprite Mark III had a great deal in commmon with that of the larger MGB. The wider location base for the rear springs allowed B.M.C. to put more rubber into the shackles. This provided quieter running as well as a better ride. Final drive vibration evident on the earlier model was all but gone. The handling was light and predictable, and there was ample elbowroom with two large people on board. These changes helped the Sprite and Midget compete with the then recently-released Triumph Spitfire