In my quest to squeeze a few more horsepower out of my car I came across this good article.


Rounding off the end of the side electrode as shown here reduces the peak temperature seen by the electrode so moving away from the possibility of detonation from this source. Also, in the relatively swirl-free conditions that exist at low rpm, this form gets the charge burning more effectively. Be sure to cut the electrode so the end of the tip is no further than half way over the center electrode. If plug life is not an issue cut it so it is between a 1/5 and 1/3 of the way over the center electrode.