>"Martin A. Secrest" wrote:
>
> OK, I have to ask -- what's spark plug indexing?
>
> If I had to guess, I'd say that's when you file a "Champion" under "C,"
but I'm
> pretty sure that's not what you mean ...
Martin:
Here's what NGK says about indexing: for more, check out their tech
section at http://www.ngksparkplugs.com/Pages/techtips.html
"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. "
Don Marshall
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