Looking to replace the ancient plugs in my Commando, and I realized that none of the replacement charts show a unique plug for the Commando. They just show the same plug for every small block. The FSM shows N10Y for the 273-4, N9Y for the 340, and N14Y for everything else — this makes me think that there was something about either the dual point distributors or the high static compression ratios that mandated different spark plugs (probably the latter). What's frustrating is that I can't find any crossover charts that list the N10Y so I can find a replacement (and I know that Champion recalibrated their numbers sometime in the interval). And manufacturers today don't even tell you what the heat ranges of their plugs are, to enable you to choose a hotter or cooler plug. The engine had N12Y in it (at least 12 years old), but they were fouling up pretty bad. Any suggestions? I am thinking the plugs from a 340 would actually be a better match than those for a 2 barrel, low compression engine.
