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SparkPlug Indexing



This is from the NGK website.
3. Indexing

              This is for racers only !!

              Indexing refers to a process whereby auxiliary washers of
varying
              thickness are placed under the spark plug's shoulder so
that when
              the spark plug is tightened, the gap will pointed in the
desired
              direction.

              However, without running an engine on a dyno, it is
impossible to
              gauge which type of indexing works best in your
engine...while
              most engines like the spark plug's gap open to the intake
valve,
              there are still other combinations that make more power
with the
              gap pointed toward the exhaust valve.

              In any case, engines with indexed spark plugs will
typically make
              only a few more horsepower, typically less than 1% of
total engine
              output...for a 500hp engine, you'd be lucky to get
5hp...while there
              are exceptions, the bottom line is that without a dyno,
gauging
              success will be difficult.
Dennis Sly.
84 SVO, Silver