This article originally appeared in Light Plane Maintenance, Sep. 2007.Spark plugs. Those pricey little fire-starters screwed into each cylinder can tell you much about the health of your engine and perhaps about your operating technique. Like anything else, learning to remove, read and reinstall spark plugs takes some knowledge and practice, but it's something that's well worth your effort. It is definitely not the same as dealing with automotive plugs, so you may have some things to both learn and unlearn. The list of tools you will need begins with a six-point, deep-well socket and socket wrench, and a 7/8 or 5/8 open-end wrench, depending on spark-plug type. (The special, very expensive, Champion spark-plug socket is nice to have because it's magnetic, extra deep and also designed to protectively cradle the plug.) You also need a torque wrench (3/8 drive is the best all-around choice), and an inexpensive plug sandblaster (or, better yet, access to a high quality blaster/tester) with proper blast media. You will need cleaning solvent such as methyl ethyl ketone (MEK) or acetone for cleaning the firing ends and cigarettes, and some anti-seize compound for the plug threads. Don't forget to buy new or use annealed plug gaskets, since reusing the old ones without annealing them is a no-no, and definitely asking for cylinder-gas leakage. Lastly, get a plug tray if you don't have one, or make one. They are ridiculously priced for what you get but some form of tray is an absolute necessity. It will allow you to easily keep track of which plug goes where (so you can use the plug to help determine cylinder health) and to avoid dropping one off the bench. A dropped plug is a throwaway every time it happens. The plug internals and tip are too delicate to tolerate dropping of any sort, and a crack in the ceramic is not always readily apparent ... but your engine will know very fast, to its detriment.
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