Always run the hottest plug you can, not the coldest. We make over 1,400hp and spray an additional 900hp in the engine on NGK -10's. 11's are to cold for us. It is a non projected tip -10. Engine compression is 14:1. -10's is what most of the guys in our classes run. Some spray 600hp and some spray 1,200hp. All engines are between 13 and 14:1 using -10 plugs. Use a non projected tip -8 on motor. If it still looks like its not hot enough then put a projected tip -8 in and take some timing out to start. Make some runs and check plugs, then add timing as needed.