Neat-O, Barney! Excellent info! I never thought about it that way.
Mostly, I like that this method makes up for errors due to FWT.
Barney Gaylord wrote:
> You can adjust the valve gap on a stock MG engine without using
> either a click adjust or a feeler gauge. Rotate the pushrod with
> your fingers. Turn the adjuster screw down to close the gap until
> the pushrod stops turning (zero clearance). Note the orientation of
> the slot in the adjuster screw, and think of a position at right
> angles to it (make an "X" with your fingers). Rotate the screw
> anti-clockwise 1/4 turn (or 91 degrees if you prefer), and lock down
> the jam nut. That's it, resulting in a perfect .015 inch gap.
> It isn't magic. It is a result of 24 threads per inch and 1.42 to 1
> rocker arm ratio.
> The math is: 1/24 x 1/4 x 1.42 = 0.0148
> You would have to miss the rotation angle by 6 degrees to have an
> error of.001 inch.