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Spark Plug Indexing

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Old Dec 6, 2009 | 12:23 PM
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From: Roggen, Co
Default Spark Plug Indexing

Has anyone on here ever done this? Like a few of you out there, I just watched on Horsepower TV how to do it and it makes sense why it would work. I guess for 15 bucks its a cheap mod.

To explain it if you've never heard of it, its pretty simple, when you screw your spark plug in the open side of the gap isnt always going to be facing the main part of the combustion chamber, indexing ensures the open side of the electrode is facing the chamber. The indexing washers just tighten your plug up sooner so the open side is facing the chamber. I guess its similar to sidegapping, just easier.
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Old Dec 6, 2009 | 12:32 PM
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it's a minimal gain for the time it takes to do...you may go thru several sets of plugs before you can get it right...

Not every hole in the head is tapped the exact same nor is the thread on every plug...

you could spend hours getting every plug in every hole right and might spend for 3-5 sets of plugs....for maybe .5 hp...not worth it to me...racers have long past that mark...better plugs are now available that can make more power regardles of where the electrode winds up being....

Use Copper plugs with a stock coil and Platinum plugs with a hiperformance coil...and ALWAYS use a brass cap and rotor....
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Old Dec 6, 2009 | 12:41 PM
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Actually they make copper indexing washers...when you buy them it comes with 3 sets of 10 thicknesses, .010, .021, and .031. You dont buy several sets of spark plugs to find the right set that will line up.

I already know bout the whole ign setup...brass everything, copper plugs, wider gap, I went with the 9mm ford racing wires and a 60k coil. I havent got to test drive my truck yet with all the ign goodies on it due to my fuel system woes...Thanks to the blindingly slow speed of the USPS.
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Old Dec 6, 2009 | 01:26 PM
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I also saw the show on Spike... I was wondering the same thing
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Old Dec 6, 2009 | 01:37 PM
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like I said...I have done it...the gain is very minimal....for stuff like we have...you get better performance and better gains doing the other mods as he has already...

Indexing becomes more important when compression is higher and you run a Domed piston where you will have issues with flame travel...

but even in these situations I cut the electrode clean off and run a very high output MSD coil...this isnt a street duty coil...

more important under boost condition where the cylinder pressure can actually blow the spark out before the gasses catch fire...
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Old Dec 6, 2009 | 03:06 PM
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I just sidegapped my coppers (.054) and called it a day. If you can tell the difference between that and Indexed plugs on a stock engine, I'd be amazed!

Last edited by ymeski56; Dec 6, 2009 at 03:09 PM.
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Old Dec 6, 2009 | 09:00 PM
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Me too. I cut the electrode short and gap to the side of the center thing in the plug.
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Old Dec 6, 2009 | 09:02 PM
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I kinda figured it was pretty similar to sidegapping, except sidegapping is free.
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Old Dec 6, 2009 | 09:20 PM
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Originally Posted by farmer12
I kinda figured it was pretty similar to sidegapping, except sidegapping is free.
Indexing is just too time consuming for the return. With my luck I'd cross thread at least 1 plug before I was done. Here's a Sidegap link if you need it:http://performanceunlimited.com/docu...degapping.html
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