This is from NOS:
Spark Plugs and Nitrous Oxide:
What Works, What Doesn’t, and Why
Over the years there seems to have been a great amount of technical material written about the simple operation of a spark plug and what they can do in relation to the way an engine runs. There are a few basic characteristics about spark plugs that you need to know to make an intelligent choice about the correct spark plug for your application.
First, and most important; a spark plug must be of the correct design to operate within the environment of your engine, not the other way around. This means that the spark plug has virtually no influence on how the engine burns fuel or runs in general. The correct spark plug will simply survive the conditions present in your engine. A spark plug must maintain a
certain temperature to keep itself clean. The wrong heat range can cause an overheated plug or a fouled plug. The heat range refers to the temperature of the ceramic material surrounding the center electrode. Lean air/fuel ratios are more difficult to light because there are less fuel molecules in the area of the plug gap when the plug is scheduled to fire; thus, projected nose plugs were designed for late-model lean-burn engines. Modern high-energy ignition also allowed larger plug gaps. All the while this was happening, something else happened.
Something that no one seems to have really noticed as the real culprit when the issue of factory type plugs being used with nitrous comes up. We’d like to clue you in. Quite often, a factory type, wide-gap projected plug will produce a misfire condition after only a few seconds of nitrous use. The misfire is not due to the heat range. The misfire occurs because the ground strap of the spark plug becomes a glowing ember because it is too long to dissipate the extra heat produced by a nitrous-accelerated burn condition. The correct fix for this phenomenon is to replace the plugs with one that has a shorter ground strap. By doing this, you will shorten the path for the heat being absorbed by the ground strap. You can use the same heat range, you just have to find a non-projected nose plus with a shorter and preferably thicker ground strap. If you only change the heat range of the spark plug to a colder heat range, you may very well still have the misfire problem. Since the length of the ground strap is the cause of the misfire, a colder spark plug may have the same length of ground strap as the hotter plug you replaced it with.
Spark plug gaps should generally be .030" to .035". Never try to gap a plug designed for an .060" gap down to .035". Find the correct non-projected nose plug designed for an .035" gap.
