Re: Spark Plug Gap
The recommended plugs are Champion L77JC4 or QL77JC4 gapped at 0.030"
The latter are inductively suppressed, denoted by the letter "Q"
The NGK plugs you mention are resistively suppressed , denoted by the letter "R".
You should not be using resistively suppressed plugs.
They are also a couple of grades on the cool side.
If you must use NGK then the equivalent of L77JC4 is B7HS-10
and the equivalent of QL77JC4 is BZ7HS-10.
The Letter "Z" denotes inductive suppression.
However they are are only equivalents and may not be the best suited for your engine.
See
HERE for an explanation for the need to use inductively suppressed plugs rather than resistively suppressed ones.
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