turning prop backwards
When moving the prop, I've always turned it backwards so the mags wont fire if the grounding is faulty. Now with my new O-320 I'm being advised not to turn backwards because the vacuum pump seals might be damaged.
My recollection is that there was a thread about this here many moons ago - I seem to recall consensus was that the dont-turn-vacuum pump-backwards story is the aviation equivalent of an urban myth ?
Cant find the old thread using the search function, maybe someone can confirm.