No Perry I don't really notice it as a miss untill doing the warm up mag
check on the ground later.  It tends to miss more at below normal combustion
temps and takes a little longer to warm the combustion temps up coming from
a low rpm going to a high static or for take off. Most of this is oil burn
off from the plugs as my engine dumps a little oil on the lower ones after a
shut down.  If they have just been cleaned recently from all deposits (Lead)
they mis less infrequent at the lower colder rpms.  This is just in the warm
up or going from a botched landing to a go around where I'm at idle and
increase power for the go around.

Most of us who rent never really see the plugs at the 100 hour inspection or
even feel the degrading performance because the AP's who do the 100 hour
clean and usually re-use the plugs as they complete the 100 hr inspection.
Most of the time on aircraft type plugs the build up starts at the bottom
and works itself up to the center and end electrode if left unchecked.  This
is when it really starts to miss and breakdown.  This might help, take one
of your plugs and knock some of the deposits off and send it in for an
analysis like to one of the oil sample companies (call first) and their lab
can probably tell you just what it really is.  This may help you to isolate
the problem too.

As too the design of the plugs aiding or abetting this problem only in my
humble opinion, I seriously doubt it.
What Bill Jepson had to say on the oil, I would really look toward his
suggestion.  All of this may be tied together.  With the sample sent to a
lab, you'd have more to work with knowing for sure just what it was.  I know
this is a real dumb question, but what color are the deposits you're
finding?  Are they soft, med hard, or hard like rock?
Where are they forming on the plug the most?  Forming anywhere else besides
the exhaust?

I don't really remember, the plugs didn't really look any different than
any other
time you remove a plug. I think I cleaned them in acetone and had to do
a little
light scraping. Maybe the lead contamination is more like a film over
the electrode
surface?

Perry

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