Armstrong Siddeley Motors internal memo re LWK 444

From Mr Cutler to Mr Chapman: In addition to the replating of the radiator grill, bumbers etc, which has been carried out during your absence, a thorough investigation to establish the cause of the fall of engine performance was immediately to hand. On stripping the engine it was found that several exhaust valve seats were in poor condition, this trouble had obviously been caused through slight sticking of the valves, which were fitted with the very first prototype single return spring, the outer spring being used only to return the rocker mechanism, The design was abandoned a considerable time before the engine was put into production and our main endurance running has been carried out on the present production type of valve mechanism, which is of the normal two spring type with the collar attached to the valve in the normal way. New valves, guides, collars and springs were fitted and the mechanism is now completely to production standard, including the camshaft. The engine compression ratio has been raised to 7:1 to bring the engine up to date and to take advantage of the premium fuels