Posted for Walter Atkinson <walter@advancedpilot.com>:

 John:
 
 You have it right, except that if you had poor F:A ratios, you'd end up with
the leanest ones just ROP--the very worst place to be for the valves.
 
 I had to laugh when I bought my Twin Beech and all of the old hat experts
were telling me to run it rich or I'd burn it up.  None of them had ever seen
an engine monitor and I'd take them up and ask them to show me the *right way*
to lean the engines.  These engines have acceptable F:A ratios so leaning them
to roughness and richening to smoothness left ALL of these engines about
50-75dF LOP!  NONE of these old experts believed what the engine monitor was
proving,..  that they had been running them LOP of over 50 years and never
knew it!
 
 Get used to believing the DATA rather than anyone's opinion.
 
 Walter
 
 
 On May 30, 2006, at 6:12 AM, Halle, John wrote:
 

"""
 All this was interesting to me in an academic sort of way until I started
thinking back on my early training (back in the late 60s.)  At that time,
there was (I think) a single engine temp guage (pretty sure it was egt from
one randomly selected cylinder) on the Cherokee 140s on which I trained, but
there may have been no engine temperature guage. Without regard to any guage
that might have been installed, I was taught to lean for cruise by slowly
leaning the mixture until the engine ran rough and then enrichening it enough
so that it smoothed out again.
"""