when i'm comparing heat range between different plugs I measure how far down the porcelain goes in the body of the plug before it bottoms out. the shallower the colder; the deeper the hotter. I always prefer the tip as far in the chamber as possible without any interference with the piston or valves. I always measure ohms resistance.
Good info , thanks.. measure ohms from the plug tip to the electrode?
yep. I've seen resistor plugs run anywhere from 3500 ohms to 15000+ ohms. some resistance in the secondary wiring is good but I try to avoid anything around 10,000 ohms for the plug and wire. capacitive discharge ignitions need some resistance, inductive ignition seems to be fine with less.
