James,


I would not recommend this glow-plug for any engine larger than a .30.

[link=http://www.os-engines.co.jp/english/line_up/plug/plug.htm]OS themselves say it is unfit for such engines[/link], except for break-in, where the rich mixture would counteract the engine's tendency to detonate on such a hot plug.

You would need a medium-cold plug for your engine. The OS #8 is the hottest OS plug that should be considered appropriate.