The ChampionL92YC has just a bit longer reach with a few more threads - it gets your spark in the combustion chamber a little better. The stock-style plugs are slightly shrouded. I think it starts better with these - others say it too. If you have the heads off, you can screw one in and kinda see where you're at . . . ok with standard compression pistons, but you should double check anything with big domes.