Aston Martin Engine Development: 1984-2000. Arthur Wilson L.

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      Figure 5.2 February 1982 – Nimrod shakedown testing at Silverstone with Ray Mallock in the driver’s seat. This was with the carburettor engine shown in Figure 5.1.

      During my time with AMT, I worked on a number of varied and interesting engine projects, including the 1.3-litre Frazer Metro, the 2.8-litre Tickford Capri and marine engines, as well as race and road AML projects. The 1,000 horsepower racing marine engine and the twin-turbo Bulldog are mentioned later in this book.

      The AMT Group C endurance race engine project was a three-year project started in 1981 for the 1982 season, and was aimed at the new fuel limit regulations that were to be introduced for the 1984 race. I don’t think anyone expected too much from the first year, the car was new and the engine would also be new as a race engine. Getting the two to work together while developing cooling systems, engine mounts and intake and exhaust systems matched to the aerodynamics of the car, etc. – there were bound to be teething problems and there were bound to be engine casualties while developing the car. Nobody goes into racing at this level expecting a free ride. In 1982, the first year of racing, we had our problems – such as the distributor rotor arm breaking due to vibration; this was easily solved and further to that the distributor was moved to the centre of the V for 83. There were also losses during cooling system testing in the car, and one car stopped during its first race at Silverstone due to the timing chain tensioner coming loose. But we had one problem that we didn’t expect and that was that we could experience valve spring breakage after six or seven hours of race conditions. It only happened in the car, we couldn’t break springs on the test bed even after running the equivalent of two 24-hour races. The only way that we could replicate the failure was to run a cylinder head test rig at 7,800 rpm continuous. At the time the engine was limited to 7,500 rpm. The test rig was based on a cylinder block, with an electric motor driven dummy crankshaft driving the standard half speed chain drive to the camshafts of the test cylinder head. Understandably things were getting a bit frantic as the 1982 race season was already underway, so we ran the test rig night and day to arrive at a solution. Everything was thrown at resolving this totally unforeseen problem, including burning a lot of midnight oil. The eventual solution involved new special surface treatment Schmitthelm valve springs, stronger valves with a reduced dish in the head and stronger top spring retainers. The last two parts were to ensure that the fitted spring length did not open up and allow the springs to go into surge. Despite this concern the car – entered by Lord Downe and run by Richard Williams – did very well in its first season, coming third in the championship. It ran very well at Le Mans that year, running consistently in fourth place for some considerable time until, in the early hours of Sunday morning, the engine started to use a lot of oil and eventually lost a cylinder. But with some careful coaxing by the RSW team it got home in a creditable seventh place overall, the fourth Group C car.

      I did an inspection report on that engine when we got it back to AML after the race. I have to say that it is the only time that I have ever seen a completely wornout Aston Martin engine. Valve guides were worn, piston rings were rattling around in their grooves and pistons were worn in the bores. The crankshaft was not too bad. It seems that – due to some aerodynamic effect – the air intake for the engine was vacuum cleaning the race circuit, taking in road grit to the engine in the process with the inevitable result.

      For 1983 the engine was extensively redesigned and lightened. It also became used as a stressed member for the EMKA race car. Further improvements were made to the valve gear, and peak power rpm was reduced to 7,000 rpm in the interests of durability. The EMKA was a beautiful car, built very close to the regulation weight. It was prepared and run by Michael Cane Racing and had a great deal of potential but needed development – it was its first year after all.