The valve travel in full gear is 5″, rather greater than most of her contemporaries and one can only argue about the somewhat excessive preadmission – typical of the era. Nevertheless, the engines were noted hill climbers and free-running in character.
As with many other designs, a new CME eventually carried out some rebuilding, the primary result being the complete destruction of the Class 8’s attributes. Nobody seemed to discover why. Neither the drivers nor the running people could understand why the performance was so lacking and Mr. Smith told of a shed fitter almost sacked for hacking at a slide valve in an effort to improve matters! The reasons are obvious on inspection. The rocker had been deleted and a heavy bar substituted, albeit with a guide to relieve the valve spindle glands, making the drive direct but with a massive offset. Quite apart from the dubious mechanical engineering the major transgression of directly driving outside admission valves via launch-type links is inexcusable. The angularities so neatly dealt with in the original design now added together to produce very poor valve events. In 1950 Whitelegg denied all knowledge of a problem, but who would be brave enough to tell him at the time?
Thankfully, I was able to explain the reasons to the perplexed David Smith in his 81st year, thereby exonerating his revered designer. The table portrays the excellent cut offs of the Manson gear.