The information I received in the Savvy Aviator seminar is:

A regular, one minute cycle of about 50 to 100 degrees (I think that
was the number) of EGT for one cylinder is an indication of a burned
(not sticky) exhaust valve that will fail, typically 100 hours after
first indications. The mechanisim seems to be that the valve rotates
as it goes up and down, about one rpm. Every time the nick in the
valve meets the nick in the valve seat extra gas escapes. Once you've
seen the plot of this, it shows up like a neon light.

- Steve Mills
N2679V 'Vicky" @ PDK
Cardinal RG '75



On Mon, 10 Dec 2007 06:18:02 -0800 (PST), Jay Honeck
wrote:

What I have started doing is looking at average, peak-to-peak variation, and
standard deviation on each channel, over a half-hour or so of stable cruise.
I am watching for any trend or sudden change in variability of data on a
channel. Doesn't tell all, but I hope it will alert me to something going
awry, whether it is engine or sensor. And it was easy to do in Excel.

In another forum a guy mentioned that you want to look for
fluctuations up and down in EGT, as it is an early indicator of a
sticky valve.

The question, of course, is what's a "normal" fluctuation, and what's
"abnormal"... Looking at my data most cylinders go up and down 10 to
15 degrees pretty regularly...

I'm assuming that's "normal" because they're all doing it -- but it
would be good to see some hard data on what these lines actually mean.