Originally posted by Big Jim:
Contrary to common belief, a colder plug does not generate more horsepower in and of itself. Too hot of a plug will wear faster and too cold of a plug will foul too easily. Unless you have made extensive modifications such has much higher compression or huch wilder cams, don't mess with it unless you have studied the subject in depth.
Unless you have S/C, T/C, bottle, or increased compression, stick with the OEM specified heat range. I'm doing OK with the colder plugs on my 3.0 w/SVT heads, but they are due for a pull to really check them soon.
