So, I am guessing by this thread that it is ok to use the none shrouded stock NKG plugs. I have not looked, but now assume that the more standard type automotive plug fits even with it longer electrodes extending further out.
There are a very large number of tip designs available in spark plugs. In engines with cast iron heads you find short (low reach length) plugs with extended tips. Where the porcelain is visible in a side view.
You can also find very long reach plugs with extended tips. It may be possible to install one of those plugs and find that the ground electrode has touched the inside of the housing.
None of the plugs in the picture is long enough to touch anything. The longest is the NGK and it is passed out to competitors by Mazda Competition department (Mazda Comp) for use in rotary engines.
If there is the slightest bit of discomfort about changing plugs, then stick with what you have now. The cold racing plugs tend to foul do to the low tip temperatures. But any plug is going to foul with lead salts in 100LL. Going to a higher heat range is out of the question as far as I'm concerned. Too much chance for damaged porcelain or a melted out plug hole. Same thing for a piston engine. Take a set of new plugs and a wrench with you always.
I use a tiny paint brush to apply Nickle antisieze to the first few threads of each plug. It is conductive, so don't get it on the tip. Torque to the lowest number for your engine. As in: if it says 14 to 16, use 14.
Lynn E. Hanover
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