By locating top dead centre and then rotating the engine backwards until the center portion has dropped 11/16ths your IH engine is now at 45 BTDC.
Not sure if I would trust this to measure exactly how far the piston went down on an ironhead. The spark plug goes in on an angle and is not going straight down into the top of the piston so the angle would give you a false reading. I bet the spark plug was on the top of the head on your race bikes.
Itís not really your bike unless you work on it yourself!
"Believe nothing, no matter where you read it, or who said it,
no matter if I have said it, unless it agrees with your own
reason and your own common sense."
-Buddha (536 B.C.-483 B.C.)