Originally Posted by Crossfire451
I understand what your saying, the other structures around the center electrode may interfere with the flame "kernel", In my saw's case it may be just the fact of a new plug made it run better. In my haste to post I might have overstated the plug's benefits. Several companies make special washers for plug degreeing. I've always read that ultimately the gap of the plug should face out into the cylinder or towards the intake valve to take advantage of the swirl affect around the intake valves
I have an old snap-on plug tester and cleaner that, along with my multimeter, I used to test several plugs and the validity of the manufacturer's claims earlier this year to write a thermodynamics and electrical conductivity paper. it was quite lengthy and I can do another series of tests for everyone if they provide my with the plugs. I will charge the plugs with a battery of tests: conductivity, heat dissapation, dynamic resistance, static resistance, spark distribution, and spark output, as well as anything unique someone wants to know, as those were the criteria I used in my paper.
majority of the people that make the claim about plugs having "drastic" improvements are those that do have worn plugs and replace them with new ones.
typically you index the plug so that the gap is facing the intake valve or the space between the intake valves (like us). washers are generally not required because the manufacturer provides you with a range of torque specs, i.e. 11 to 15 ft/lbs, for indexing purposes. you are correct about this aiding in the swirl effect and it is also to prevent plug-to-piston contact in nitrous-fed, F/I, and high c/r vehicles.