There aren't any non-RC plugs, actually there aren't any RC plugs either....there's just glow plugs . Choosing a plug for an unthrottled engine is much the same as choosing one for an RC engine, apart from not having to worry about how it idles or transitions. Although come to think of it, I guess you could say they transition from not running to flat out as soon as you give them a flick. Most of the time you can barely detect the time it takes to reach full speed . My favourite plug for engines that I run 4 stroking rich is the Taipan red (hot) plug. There's no discernible rev drop when the glow igniter is removed. This is with zero nitro fuel so it could possibly be too hot for nitro.