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Indexing spark plugs........myth or fact?

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knighty

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I have loads of customers come to me getting all excited about indexing spark plugs.....a year back I spent a few hours on my dyno trying all angles possible.......plus specifically pointed at the inlet and then pointed at the exhaust valves........it made absolutely no difference to power at all.......engine was a 7hp gx160, spinning to about 6400rpm.......but I did find a difference in power between spark plug types, the plug gap, and coil types.......

Whats the general feeling here on indexing plugs?.......I feel its only really relevant to huge-power motors........happy to be proven wrong
 
It’s more of a flathead thing as far as im concerned. If I was them I would spend more time making sure they use the proper plug, with the proper heat range. Just my 2cents.
 
Cheers guys - I value your opinion.......I have loads of motors come to me with a paint-pen stripe down the open gap side of the plug where its been index'd toward one of the valves by the previous builder.......it was starting to bug me.........I really feel these builders were at the edge of their knowledge-base and essentially clutching at straws, just trying to wow their customers with fancy talk over what is essentially nothing, what is known in the medical industry as a placebo effect........the gains I find on my flow-bench, which are substantial, absolutely trump the hell out of any minuscule gains I ever found in the ignition system!

15-20 years ago I was deeply involved with the design and development of IRL motors for TWR (Nissan-Infiniti), WRC for Hyundai and Ford, BTCC for Proton and Peugeot, LeMans for Reynard and Ascari.......never once did we ever index the spark plugs!!!!
 
I also did research on the dyno for indexing and found nothing. Now with that being said, my dyno isn’t one that will measure that kind of a miniscule change. You need a super sensitive to change dyno for that task. Back in the day when we were indexing the spark plug in the flat head it was for the purpose of not allowing the intake valve to strike the ground strap on the plug and shut the engine off
 
Thanks for this info. I have never indexed a plug. I could never buy into it. I don't see how an explosion would care where the ignition is pointed. I have worried about this for years. Never had a dyno to test it. Thanks a bunch.
 
I can confidently say my Dyno is super sensitive. I find the real fine gains are detected in the spin duration time......my dyno measures down to 2 decimal places. 0.05 seconds gain on the dyno usually equates to around 0.3 seconds on the track.......this relationship is well proven over 3 years and over 6000 dyno pulls and hundreds of customers motors with plenty of wins........indexing the plug was worth zilch.
 
Thank God! I have never indexed, and didn't figure it could matter to the explosion, but never had empirical data to back it up... Nice to know I only have to work on the 10,000 other variables now.
 
Exactly, everyone with the clones are running the 3910X which is gapless, so it doesn't make a difference anyway. lol

We run a much hotter NGK projected tip plug, works very good in restricted motors that are pulling tons of fuel.

Now if you want to really test plugs on your dyno and see a difference, I'm told the plugs from Brisk will add power that is noticeable. But at $15-20 a pop I can't justify it. Would love to see one of you guys with time, dyno and some extra cash do it though!
 
1fasttiller said:
Exactly, everyone with the clones are running the 3910X which is gapless, so it doesn't make a difference anyway. lol

We run a much hotter NGK projected tip plug, works very good in restricted motors that are pulling tons of fuel.

Now if you want to really test plugs on your dyno and see a difference, I'm told the plugs from Brisk will add power that is noticeable. But at $15-20 a pop I can't justify it. Would love to see one of you guys with time, dyno and some extra cash do it though!
Click to expand...
we ran gapless in the flatheads as well, ngk bu8h
 
I agree if you gain anything for $15-20 how can you say that is expensive, you spend hundreds of dollars in search of miniscule gains. I am of the camp the only gain from properly operating, gapped correct heat range plugs is the change in compression ratio.
 
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