My view is that a spark plug is like a factory worker -- you replace them when they no longer do their job.
We replace them at every engine rebuild (some have been run a fulls season or more.)
Likewise, we have customers that replace them every race day.
I personally see no reason to replace a spark plug if it is sparking when it is told to.
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cut
z
www.CarlsonMotorsports.com
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33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com