I guess I need a simple primer on which plug is appropriate and why? I
have a 1970 TR6 that has been modified with higher compression, cam,
elec. ignition, etc. I have been running the Champion 9Y and the car
runs great. I've pulled the plugs numerous times and they look good.
Both my manual and the TR6 worshop manual say to use the 9Y. Even
Kastner's Competition Preparation manual recommends the Champion 9Y for
modified cars that are not full race prepared. If this is all the case,
when (and why) would a 12Y plug be appropriate. I have noticed that in
the Roadster Factory fliers they sell the 12Y plug for cars that need a
"hotter" plug. Could someone just go over the basics of plug choice and
the reasonswhy? When would one chose the 12Y over the 9Y and vice versa.
Thanks.
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