[TR] Turning engine backwards?

[Paul Dorsey]

List,
I may have asked this in the past.  If I am handturning my TR3-4 engine with
the fan blade in an effort to determine TDC (carefully using a McDonald's
straw down the spark plug hole to gauge piston #1's exact highest point).  If
I turn the fan blade clock-wise till the moment the straw stops climbing, then
I think I am alright.  However, if I pass that point (even by 1 degree) so
that the straw starts any downward movement THEN I SHOULD NOT (EVEN SLIGHTLY)
BACK THE FAN BLADE IN THE OPPOSITE DIRECTION (CCW) DIRECTION lest I introduce
slop to the drive chain--IS THIS CORRECT?

CAN I GO A 1/16TH" SMIDGEN CCW?

Will it do the motor definite harm if I go an inch (turning the fan) in the
wrong direction?  Mind you, I'll refrain from this- 'but what if a friend
turns it an entire revolution backwards before I catch him?'

Thanks,
Paul
60 tr3 (w/ a TR4 engine)