Reading Spark Plugs  Thanks to Larry Meaux of Meaux Racing for
providing this information and pictures.  Plugs are best viewed
with a 10x power illuminated magnifying glass.  Heat Range:
Heat Range = Ground Strap, the ground strap indicates the heat-
range of the spark plug. If the "color" of the ground strap
"changes" too close to the ground strap's end, (which is above
the center electrode), then the heat-range is "too cold" ,
meaning that the strap is loosing heat too quickly to the base
ring, and is not able to burn off deposits until near its end.
If the "color" of the strap changes near where it is
welded/attached to the base ring (last thread ring), then it
means that the plug heat-range is "too hot", because heat is not
being tranferred/cooled from the strap to the base ring quickly
enough !!!! The strap might begin to act like a "glow-plug",
eventually causing preignition and/or detonation later on.
Proper heat-range is when the "color" is at the half-way point
on the strap, neither too cold or too h