H. W. Stephenson
By Dan Wilson
Philip Dayson says:
> Mr. Stephenson says "variation of valve lift anywhere between 0.020"
> and 0.075" has no significant effect, so that it would not appear to
> be worth while to lavish time and care on determining what clearance
> to use, or even on effecting uniformity. ... Anywhere between 0.035"
> and 0.050" would be likely to be satisfactory."
> This statement is absolutely _contrary_ to the opinion of most
> restorers. Why the difference?? I have no reason to doubt the
> accuracy of Mr. Stephenson's work. Is there a factor other than
> hammer velocity at work? Any comments?
I'm not a restorer but I am sure Mr. Stephenson's assertion would burst a few blood vessels amongst those I know. The whole point of accurate valve settings is not loudness but loudness balanced against rapidity of action. There's a point at which reducing the travel begins to choke the instrument in rapid repetition and you go for a setting just above that.
Hugh Stephenson contributes long articles of much this same character to the PPG Bulletin. Amongst the restorers I know, they are treated with tolerant skepticism. The proof is in the pudding.
Dan Wilson
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