Mike -

The spark plug info you're getting from others is pretty much correct. I'll add
some info here about ignition system maintenance:

1 - Check and service spark plugs every 100 hours (+/-10). I typically have mine
serviced by Aircraft Spark Plug Service Inc 16152 Valerio Street, Van Nuys, CA
91406 (818) 787-5680. They do a full service on the plugs (test, clean, paint,
and repackage) for about $4 a plug. They come back looking like new (except for
the wear of course). The Champion rep doesn't like them much for various reasons
(one is they remove the original paint off the plugs) but I've been happy with
them. (I have two sets of plugs so I don't have down time).

2 - Check the ignition wires where they go into the plugs. Springs should show
now signs of arcing where they contact the plug. If they do a little VERY light
touch with a fine stone on a Dremel tool knocks it off. Also be sure the
"cigarettes" (rubber part) are clean and dry. You can clean them with MEK and a
cotton swab (Q-tip). Be careful not to allow the wire to twist at the spark plug
when you reinstall them.

3 - Slick mags should be serviced EVERY 500 hours using the inspection
procedures outlined in their service manual. Specifically I recommend changing
the contact points regardless of condition, cleaning the inside, and removing
the build-up of material on the end of the contact arm of the rotor and each
contact inside the rotor cap. To do this inspection requires having the Slick
technical data and proper tools. DO NOT just crack into a mag without proper
knowledge or tools.

4 - Pressurized mags require extra care including checking inlet filters and
being VERY sure the bleed orifice in the mag is open. If it isn't, moisture
combined with sparking action inside the mag creates nitric acid (if I remember
correctly) and the results are disastrous (and REALLY ugly when you open the
mag). If this happens it's best to just buy a new mag.

5 - Every 100 hrs check the magneto to engine timing. The timing will typically
change over time as the INTERNAL timing of the mag changes (a function of point
and/or cam wear). Engine timing should be dead on within a degree or two per the
engine manufacturer's specification (some limits are even -1/+0).

Ted Stanley - A&P-IA / ATP