Angier,

I've had our 320 to FL210 on a few occasions.  It gets up there only if you're quite light (solo, minimum baggage, low fuel). It's only a practical altitude if you're catching a big tailwind.  IAS is only around 115-120 so any turbulence would necessitate an immediate descent.  With a 360 you could get up there a bit easier and have a little more airspeed margin.  You should have either electronic ignition or pressurized mags in addition to the stuff that Greyhawk mentioned.  I guess it all depends on your definition of "practical" but in general, I'd say that FL180 would be about the highest practical altitude for a 320/360 on most occasions.

Bill Harrelson
N6ZQ IV 500 hrs



-----Original Message----- What is the practical service ceiling with a 180hp IO360?
Years ago I was told you are there when the rate of climb drops to 100ft/min of less.
How high will it go?
Frost bite might be the limiting factor?