#3 hole?........on the old upright engines, #3 ran hotter because the
air was preheated by the oil cooler, and number 3 was off set to the fan,
causing a lack of airflow across number 3 cylinder. The redesigned fan
shroud and a fan with more volume cured that, by putting the oil cooler out
side the fan housing. Also a little known fact about the early distributors,
The number 3 cam lobe was off set a few degrees, can't remember if it was
advanced or retarded. But by changing the timing just a fraction it helped
cool number three some.
    If I remember this was the 36 HP engines. The hot rodders would use that
fan on the later engines, as it would use less power to run it, less drag.
That and the so called "Power Pulleys" sure burn up a lot of engines back
then. I even saw a generator interrupter switch in an old Hot VW magazine
once, for the drag race boys! That way not only could you fry your engine,
you could run down your battery while you were at it. :^)

Howard

> Dakota Digital is supposed to be the most accurate and that has to be
> installed at the #3 cylinder spark plug point.