<< Chuck wrote:
<snip>
First, I

had a trailing plug fail , it broke the insulator ...

Generally, broken insulators are a good indication of detonation.  Do you have a knock sensor on the engine or some other means of detecting this condition?  It may be worthwhile to run a little richer under high load conditions till you can be certain you don't have a problem.

Second, I noticed that on take-off at the low elevation fields, which was
most of them on this trip, the RPM would be at 5200 which is normal, then it
would drop off after 3 or 4 seconds into the takeoff roll to maybe 4700.

Isn't this an indication of cavitation at start up? Once the plane gets rolling, the prop is able to get a decent "bite" which loads the engine down.

Regards,
  Peter Militch Cozy Mark IV #740

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