While the A90 Atlantic weighed 2,996lbs the Austin-Healey 100 was 1,904lb which resulted is vastly improved performance. When the Le Mans performance kit was developed after the 24 hour race in 1953 power went up to 110bhp and performance improved again.
The contract between the Donald Healey Motor Company (DHMC) and Austin allowed Donald Healey and his team at Warwick the role of promoting the new Austin-Healey 100 by way of competition and record breaking. So what better place for promoting to the burgeoning US market than record breaking on the salt flats at Utah?
History tells us that a single car was prepared in Warwick for the 1953 event, but while the production 100 was spritely enough for the average motorist, more power was needed for Bonneville.
So what was different with the engine fitted to the 1953 Endurance car?
To achieve the power needed the DHMC sough out the assistance of Harry Weslake at Weslake Engineering, who had originally designed the cylinder head for the A90/AH100.
As with any quest for additional power the first place to look is the cylinder head as the answer was to improve gas flow. Easier said than done, as not only were the inlet and outlet ports located on the same side, but the pushrods were there as well. Something had to give as anyone who has looked an original cylinder head of a 100 will see that the amount of machining that can be done to the inlet/outlet ports is limited by placement of the pushrods.
So Weslake designed a new 8-port cylinder head that incorporated the inlet/outlet ports on the other side or driver’s side of a RHD car. The location of the pushrods, being dictated by the positioning of the camshaft had to stay where they were. The new cylinder head was also designed to be cast in aluminium alloy.
The cylinder head design also meant that some alteration had to be made to the cylinder block and coupled with a higher compression, camshaft and distributor modifications as well as twin 1 � inch SU carburetors, the power was up to 132 bhp. Adequate for the 1953 Endurance car, but in the event itself, conrod failure cut short their record attempt. In case you thinking the engine sounds familiar, it was almost the same that went on to be fitted to the 100S.
Donald Healey and the team returned in 1954 with the same car, but modifications to the engine included fully floating conrods, nitrited crankshaft and lighter flywheel. The car itself was now fitted with four-wheel disc brakes and Dunlop peg-drive wheels. The main purpose of the Endurance car was to prove the durability of the Austin-Healeys at high speeds. 24 hours at constant high speed had to do the trick...
As we know, they also returned with another car called the Streamliner, which was as close to a road going 100 as chalk is to cheese. Not only was the bodywork extended forward and rearward, but the cockpit was completely covered save for a Perspex canopy for the driver’s head. It was Donald Healey’s aim to surpass the magical 200mph mark.
Here was a car that not only sported gearing for 200mph, but also looked as if it was doing all of that while standing still. However more than 132bhp was sufficient for the Endurance car it was not for the Streamliner.
Once again they turned their attention to Harry Weslake for a new design that would withstand the calculated required compression ratio of 13:1 and the rigours from using methanol fuel.
For this, Weslake cast another angle faced 100S style cylinder head, but instead of the aluminium used previously returned to cast iron for greater reliability under the strain of the sustained high speeds/revolutions involved in record breaking. Interestingly this cylinder head was designed to be mated to the block without a gasket, which required careful hand lapping. In any high compression engine the head gasket is usually the weak link.
This configuration also meant that any passage of coolant between the head and the top of the cylinder block was eliminated by plugging the water galleries in both the head and block at the faces. Of course the coolant still had to flow between the two and this was achieved by running the coolant externally from the rear of the block to the rear of the cylinder head. A header tank was mounted rear of the engine on the firewall to allow for the bleeding of air in the system.
When breathing through a crankshaft mounted Shorrock supercharger the Streamliner engine produced in excess of 240bhp.
While this was a sizable amount for any engine that started out producing a wheezy 67bhp in the Austin 16, it was unfortunately not enough for Donald Healey to reach his 200mph goal, as he managed to set an average top speed of 192mph. However he did return to the salt the following year with the supercharged 100-Six engined Streamliner, the same cars as in 1954 with a substantially more aerodynamic body, modified from its 1954 guise following further work in the wind tunnel. Sadly, Gerry Coker’s striking finned and memorable shape was no more. It is in this car that Donald Healey set 203.11mph. To this day DMH remains the fastest ever Austin powered Healey driver.
Will he remain so? That remains to be seen, as while the Healeysreturntobonneville team of course have the greatest of respect and affection for the 1954 results of the DHMC it is hoped to equal, but not surpass them in 2009. The engines of both the 2009 Endurance and Streamliner cars had been constructed using techniques as close as possible to the original, but it is hoped that the cars prepared with modern materials such as tires will achieve the required result.
By the way the entire engine used in the 1954 Streamliner still exists and is fitted to a 100M in Queensland, Australia.
Patrick Quinn
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