Jay's wrote:
"Sadly, I have to admit that our fear of harming our engine
has far outweighed our fear of an engine-out landing. There
is simply nothing you can do to your engine (in normal use)
that is worse than simulated engine-out landings, so we do
them very rarely."

I called the overhaul shop that just did a major engine overhaul on my
Lycoming O-320. First, these guys have been there for years and came
highly recommended by several independent sources in my search for a
reputable place to take the engine. I posed the question -- "How harmful
to a healthy engine is simulated engine failure practice?" I told him
that it was said that simulated engine-out practice is the worst thing
you can do to your engine.

He said he disagrees and assumed your concern was probably about shock
cooling, but said that while everyone needs to be aware of that, it is
of much greater concern with high-performance, turbo-charged engines
where people chop power and dive for the ground. With the 0-320, he said
in colder areas (I'm in AZ), you would use carb heat, and of course he
recommended what all CFIs I've ever flown with have done -- "clear" the
engine by adding some power for a few seconds one or two times during
the power-off glide/descent. Yes, that takes a little of the "reality"
out of the drill, but it is, in fact, practice/simulated.

He went on to say that if it were THAT easy to damage the engine by
pulling the power back to idle, how about when you pull the power abeam
the numbers and the hot engine is at idle through the rest of the
approach, landing and taxi and then is shut down completely (standard
practice every time for some)? He commented that it would be tricky to
just shut down a hot engine without damaging it if pulling power back to
idle is all it would take to do so.

You may not agree, and maybe your mechanic doesn't agree ... but as said
in an earlier post, if you think about all the airplanes in flight
schools that are doing simulated engine failures far more frequently
than we would (some much more powerful than an 0-320 ... I can't
remember what engine you have), there would be many more engine problems
in rental/school airplanes than there are if there's nothing worse for
an engine than simulated engine-outs.

I'm just the messenger on this one, not a mechanic, and being a girl, I
did not grow up tinkering with engines. But I dealt regularly with the
mechanics when I worked at the flight school, and I never heard them or
any that have worked on my airplane(s) say anything about simulated
engine failures being potentially dangerous to the engines.

Shirl