Which Spark Plugs with a Low Boost S/C


10 Year Member
Apr 23, 2008
NC State University
As the title says, which spark plugs do you run with a supercharger at about 6lbs of non-intercooled boost? I've read threads that say NGK TR6, but they were all at least two years old, and I can't find those particular plugs on any of the auto shops' websites (NAPA, Advanced, Auto Zone, etc.). Are they under a different part name/number now? Or if not, where can I find them?

Is there some other kind of plug that I can use (i.e. heat range, gap size, material, etc.)? I'd rather not use a copper plug on account of having to change it at least once a year, but if that is absolutely the best thing then I guess I can deal with it.
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Even at "just" 6#s (especially non-intercooled) you want at least one range colder. TR6s are common. I believe Autolite 103s are one step colder as well.

You really should be pulling the plugs fairly frequently on a S/C car to check the running condition, even at "just" 6-psi. Make sure you close the gap down some to avoid misfires under boost. Normal gap is ~0.054" I believe. I run 0.032" with a 9# pulley. You might try 0.040" or so with the lower boost.