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In the last couple of days I saw a post (or article) concerning spark plug orientation. It maintained a couple of HP could be gained by having the spark plug gap face the squish area (or intake in a hemi) and named a source for washers to control which way the plug faced in 120* increments. The problem is I can't remember where I saw it. Must be oldtimers disease. Anyone else see this?
 

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FOG
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fatbob said:
In the last couple of days I saw a post (or article) concerning spark plug orientation.
Dunno. My plugs are straight....never had to worry about their orientation. :D

The last thing I read on plug orientation was that it's essentially a non-issue unless you've got a serious performance machine and are looking for the last little bit of burn efficiency on the track.

T113
 

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Same answer as Trooper - If I recall, those looking to cover every possible variable looking for more power, "index" the plugs.

Mark the outside to show orientation, then use various thickness spacers to position plug as desired.
 

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Out of curiousity I wanted to see how my plugs faced. I pulled them, marked them then put them back in. The gaps on both plugs just happen to face the intake valves perfectly. Maybe that's why my bike is so damn fast. Or maybe it's fast because the engine is strong and the plugs don't make a difference!?

All joking aside, like others have said, unless it's a race engine it won't matter. I don't know where to get the spacers from.
 

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Ok Guys, Here's the scoop.
Those of you that read my fng rant when I introduced myself to this forum know that I work in the motorsports industry (4 wheels not 2) and own a racing parts supply/engines development/motorsports consulting company. We stock and sell plug indexing shims ( not expensive at all) for the people that insist that plugs need to be indexed. (I guess they need something else to do).
In the real world we have never been able to find any difference at all in performance either on the dyno or on the race track from indexing plugs. Haven't done it in years.

Rapid One

"When in doubt, Gas it. It won't help but it ends the suspense!"
 

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Someone will have to explain to me how it conceptually can make any difference at all. How can the 2 mm difference in spark location from rotating the plug make any noticible difference when you have a cylinder that's 4 and 3/4 inches or about 120 mm wide? Personally, I find it hard to believe, but am very willing to be convinced by data.
 

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I don't know if indexing plugs will make any difference on street bike, or anything else. What I do know is, a guy from these parts used to spend hours while on the road, indexing plugs. He won the modified eliminator NHRA World Championship in '74, I believe, with a small-block '69 Z. Dunno if the indexing was a big (or any) part of it, but it worked for him.
 

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I don't know if indexing plugs will make any difference on street bike, or anything else. What I do know is, a guy from these parts used to spend hours while on the road, indexing plugs. He won the modified eliminator NHRA World Championship in '74, I believe, with a small-block '69 Z. Dunno if the indexing was a big (or any) part of it, but it worked for him.
I'd say it worked for him if there were no other modifications to his engine, but I think maybe he did a few other things to it?
 

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In the last couple of days I saw a post (or article) concerning spark plug orientation. It maintained a couple of HP could be gained by having the spark plug gap face the squish area (or intake in a hemi) and named a source for washers to control which way the plug faced in 120* increments. The problem is I can't remember where I saw it. Must be oldtimers disease. Anyone else see this?
That's an age old track theory. Never did a dyno or have proof positive, but, I always run them that way. The theory makes sense. But I doubt it's a couple HP, a better, proper burn, to get all you can get, is all.
 

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If one really wants indexed plugs there's a far easier way to do it: E3 sparkplugs. Anyway you do it they'll always be indexed.
I read a test a few years back published by one of the hot rod magazines where they found no power difference from indexing spark plugs. Yes, it was done in a dyno cell.
Me, I don't worry about such nonsense. A spark is a spark. And no I don't use E3 plugs ( I detest the phony hype). I currently have NGK's in my scoots.
 

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Absolutely useless, I've built engines from street, to oval track and Top fuel drag bikes, waste of time, but if it floats your boat have at it, BTW there is a voltage regulator out there that really will add HP intermittently, when the battery is fully charged, it kicks out unloading the alternator drag. Compufire
 

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Ironbutt
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Complete waste of time IMO. Let's say (for the sake of argument) that indexing the plugs in your Harley did make 2 extra HP. Do you really think you'll be able to feel that extra? In my experience, it takes at least a 10 HP increase before you can really feel it. Now, if you are talking race bikes where every fraction of a second counts then maybe it's worth the effort.
 

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The last thing I read on plug orientation was that it's essentially a non-issue unless you've got a serious performance machine and are looking for the last little bit of burn efficiency on the track.

T113
This it in a nutshell streetbikes do not need to worry about plug orientation not enough gained to make it worth the effort. Then there are the fanatics so it is up to you. I fussed over it for a few years.
 
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