[Healeys] hot/cold plugs

Richard J. Hockert rjhco at att.net
Fri May 31 10:09:59 MDT 2013

The temperature rating of sparkplugs has nothing to do with how big the bang

The purpose of different heat ranges is to transfer the correct amount of
heat out of the sparkplug and into the head so that the sparkplug is
operating at its optimum temperature.  The plug has to be hot enough to burn
off deposits but not so hot that the ceramic or metal melts.

Modified racing engines make more power, which equals more heat, which means
more heat must be transferred out of the sparkplug and into the head to keep
from damaging the sparkplug.  The solution is a colder plug, which transfers
out more heat than a hotter plug.

Learn to read your sparkplugs to iterate in on the correct heat range.  NGK6
is a good place to start, go to 5 if the plugs are fouling; go to 7 or 8 if
you see heat damage to the sparkplugs.

Best regards,
Jim Hockert
Dallas, TX

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