Originally posted by Terry Haines:
OK 'aftermarket engineers' define why you need to change the heat range and 'hardness' of a spark plug.......I'm gonna love this.... 
Well, in my case I have increased compression by more than a full 'point', thus increasing combustion chamber temperatures. Ha ha, didn't think you'd actually get a good answer from anyone on this one, did you Terry? :p I did my homework on this one. I am a real engineer after all.
Not completely sure if I'm cold enough yet, but I'm as cold as I can go on double plats. A little more testing with the TR6's I have laying around to follow, but I'm not leaving them in there for long.
However, unless anyone has gone with increased compression, forced induction, or maybe nitrous (?) there is no reason to change heat ranges. Unless you enjoy fouling spark plugs.
