"Dennis O'Connor" wrote in message ...
Lotsa "depends"... One of the benefits of owning a plane, or flying the
same one most of the time, is that you get to know the idiosyncrasies... On
mine, from experience I know the proper rpm for mixture cutoff that gives
the smoothest shutdown, and 99 times out of a 100 results in both props
stopping at the same angle... Just a game I play for my own satisfaction...
There is also the method of going to 1800-2000 rpm, pulling the mixture as
lean as it will go without shutting down, wait 10-15 seconds, then gently
close the throttle to idle, wait until the engine slows, then fully cut the
mixture... This helps to clear lead fouling off the plugs...
denny

We run an O-360 with an Ellison TBI... the plugs tend to foul very
quickly, even if the engine is leaned during taxi. Therefore, our
shutdown procedure is to run up to about 1300 rpm and pull the mixture
out to right about peak. We let it run like that for 20-30 seconds,
then throttle back to about 800. Mixture is chopped to cutoff, then
we push the throttle up. As soon as it starts to speed up, we cut the
ignition off.

This process results in a clean start for next time, and the least
amount of shaking we've managed to accomplish without the engine
deciding to spin backwards for a few revs.