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Differences and Similarities-continued

493 ohv

This is the redesigned 500 engine of 1932. There are many differences to the engine of 1931, I shall attempt to list them here. The fundamental reasons for the redesign appear to have been the extremely poor sales of the 350s (so lots of parts to use up), poor oil circulation, overheating, weak gearboxes and critisism of the excess weight of the 1931 500. An exercise was carried out to see if the 350 cycle parts could house a 500 engine, this would need to use the 350 crankcases, as the existing 500 crankcases were 1 + 1/2" too wide. This (in theory) was achieved by using the 350 crankcases complete with bottom end assembly (this meant that the 350 stroke of 90mm was used, so a larger bore and piston were required). The only difference that I know of to the 350 crank components being the alteration of the timing shaft, to allow the half time pinion to be a seperate component, no longer integral with the shaft. The stroke was therefore 90mm, and the bore became 83.5mm. I suspect a number of 350 crankcases were in fact, melted down and re-cast, as this later engine had a modified integral oil pump and valve gear housing. The cam shaft also evolved to have two lobes, as the previous version had suffered heavy wear.