AHC The Big Healeys

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Origin

The original Big Healey, known as the Healey 100, was built as a prototype in 1952. It was aimed at a gap in the market between the ageing MG "T" Type and the up market Jaguar XK range. It was known that Austin were looking for a new sports car at the time and this probably influenced Donald Healey's choice of components used in the design.

The car made it's debut at the 1952 Earls Court Motor Show and by the end of that week a deal was struck between Donald and Leonard Lord for Austin to produce the car as the Austin Healey 100.

If you'd like to find out more, you could check out this article written by Rob Ransom for the 50^th Anniversary of the Austin Healey 3000.

Design

Chassis/Body

As an engineer, Geoffrey Healey was aware of the importance of a stiff chassis for good handling, and for it's time the Healey chassis was quite good. It is a ladder type chassis constructed from hollow rectangular section members; two main longitudinal members with a cross member front and back, and a strong cruciform section just behind the gearbox. Outriggers behind the front wheels and in front of the rear wheels are connected to inner sills add significantly to the torsional rigidity of the chassis. Welded to the top of this chassis is the tub, a sheet metal inner body, floor, A and B posts. This time it is the bulkhead around the transmission tunnel that adds strength to the chassis. The body and trim panels are mounted on the tub. The doors, bonnet and boot lid are in steel, whilst the bonnet and boot surrounds (shrouds) are in aluminium.

Engine

The AH 100 engine is a 2660cc four cylinder unit from the A90 Atlantic. This engine has its origins in trucks and lived on for many years in London Taxies. It is long stroke, low revving unit with loads of torque. The AH 100-6 engine is a four main bearing, six cylinder unit from the Austin Westminster, and contrary to popular opinion does not have it's origins in truck manufacture.

Initially at 2639cc, this was enlarged to 2912cc for the AH 3000 requiring a new block in the process. Early 100-6 engines had the inlet manifold cast into the head making the engine very inefficient. On the road this car was slower than it's 100 predecessor. The head was changed to a 12 port design which was retained through into the AH 3000 engine. At the same time, the connecting rods were changed from clamped little ends to fully floating gudgeon pins. This combination enabled the engine to rev more freely.

Transmission

©JB

With the torque of the A90 engine but less weight, first gear was too low to be of any use so the selector mechanism was modified to disable first gear. This gave a 3 speed box with overdrive on the top two ratios. A stronger, revised gearbox was introduced with the BN2 with overdrive on third & fourth gear and this utilised all four ratios. These gearboxes were from column change saloon cars with the result that the floor change conversion emerged from the left hand side of the gearbox. During the reign of the 3000 MKII, the gearbox was modified to a centre change with the lever emerging from the top. The Laycock overdrive was retained as an option throughout.

Brakes

Drum brakes were used on all four wheels until the introduction of the AH 3000 when discs were fitted to the front.

Variants

100 BN 1, 1953-55: two-seater roadster, three-speed plus overdrive.
100S, 1955: Racing 100 with Weslake-type cylinder head and all-round disc brakes.
100 BN2, 1955-56: two-seater, four-speed plus overdrive.
100M, 1955-56: 100 upgraded to Le Mans spec.
100-6 BN4, 1956-59: 2+2 seating, 2639cc six, length extended by 6.5in & wheelbase extended by 2in.
100-6 BN6, 1958-59: two-seater roadster, same wheelbase as 2+2.
3000 Mk I BN7, 1959-61: two-seater, 2912cc, front discs in place of drums. Two 1.75in HD6 Carburettors.
3000 Mk I BT7, 1959-61: 2+2, otherwise same as the BN7 Mk I.
3000 Mk II BN7, 1961-62: two-seater, triple 1.5in SU carbs in place of twin 1.75in, revised grille.
3000 Mk II BT7, 1961-62: 2+2, same changes as BN7 above.
3000 Mk II BJ7, 1962-63: Often known as the MkIIA; 2+2 convertible with curved screen, quarter lights, winding windows and permanently attached folding hood. Changed back to two 1.75in HS6 carburettors.
3000 Mk III BJ8 Phase 1, 1963-64:2+2 with new dashboard, folding panel behind rear seats, twin 2in carbs.
3000 Mk III BJ8 Phase 2, 1964-68:2+2 with improved ground clearance and anti-tramp bars.

Brief History of the AH 100

1952	The birth of a legend! Sensational launch of the Healey 100 at the Earls Court Motor Show. Austin's Leonard Lord concludes manufacturing agreement with Donald Healey. The car is re-named the Austin Healey 100 type BN1.
1953	While Austin's Longbridge factory is being prepared for production of the Austin Healey 100, work begins at Healey's Cape Works, Warwick, building the first BN1 models for motor shows in New York, Los Angeles and Frankfurt. A fourth car is prepared for a sales promotion tour of the U.S. The Austin Healey 100 wins the Grand Premium Award at Miami's World Fair and is acclaimed the International Motor Show Car of 1953 at New York. A standard production car is taken to Utah Salt Flats and records an average 103.94 mph in a 5000 kilometre endurance run. By the summer, production at Longbridge tops 100 cars per week.
1954	Donald Healey achieves 192.62 mph over a flying kilometre in a 224 bhp supercharged streamlined 100, while Carroll Shelby goes on to break sixteen U.S. and international speed records at averages of nearly 160 mph. Record and race achievements result in the development of the famous 100S model, the 'S' standing for Sebring. Only 50 cars are made.
1955	Production of the BN2 model commences in August but is not launched until the Motor Show in October. Changes include a new gearbox. During the period January 1953 to August 1955, approximately 10,000 BN1s are sold.
1956	Production of the 100 BN2 ceases in August, after just one year in which 4600 had been made. Total production of Austin Healey 100 models is 14,600 in a little over three years. Less than 10 per cent are made right-hand drive and only 3.5 per cent are 'home market' cars, making original UK registered models very rare indeed. Production of 100/6 models begins in August of this year.

Thanks are due to various contributors in putting together this article, including The Northern Healey Centre, Phil Gardner, Alan Cross & Rob Ransom.