Spark Plug ground strap position

[Mach1 Driver 560]

I just ran into this today, and am wondering what others think. The story is that if you point the ground strap 2-3* towards the exhaust valve (from dead center between the valves) that you will get slightly smoother Idle and better efficiency. Mark down the length of the porcelain on the open side of the strap and use copper crush washers to align it as needed. This seems like a lot of effort.

[Brian Conway 264]

Yes ' clocking ' the plugs is a bit of time and effort. Usually reserved for the track for that elusive tenth of a tenth.  Brian

[barnett468 418]

14 hours ago, Mach1 Driver said:

I just ran into this today, and am wondering what others think. The story is that if you point the ground strap 2-3* towards the exhaust valve (from dead center between the valves) that you will get slightly smoother Idle and better efficiency.

Whoever wrote that was likely smokin somethin or has a serious case of the placebo affect.

In general, indexing plugs is a complete waste of time for any street based engine.

Indexing plugs has more affect on engines running alcohol than engines running gasoline.

There is absolutely no one single position of a plugs electrode that is the optimum for all engines because combustion chambers differ in design, and the shape of the piston dome can have an affect as well.

The single easiest way to "attempt" to determine the optimum position of a plugs electrode in any engine is to run it on a dyno and test several different plug positions, however, on street engines, if there is any gain in hp, it will typically be statistically smaller than the error margin of the dyno itself, which would then render the results inconclusive.

Another method is to use transducers that will detect a misfire, then run the engine with the plugs in various positions.

The best method is to run the engine on a dyno while using tranducers.

Also, around 99.999% of the people would get significantly more hp by simply properly tuning their engine such as jetting and setting the timing curve for optimum performance than they would by indexing their plugs to the optimum position.

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[Vicfreg 771]

This is something that is supposed to be only useful for racing or really high performance use.  if your heads are off, you can try this, just get what are called "indexing" washers from Summit or Jegs. They come in different thicknesses and through trial and error, the theory is that you use the washer to limit the rotation of the spark plug while tightening it, and point the ground strap directly opposite the exhaust valve.  Meaning, that the spark plug opening is pointed directly at the exhaust valve.   

I have seen this done in the pits at high end drag races.  For most of us, not worth it.