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Indexing spark plugs; Indexing spark plugs
Topic Started: Jul 26 2014, 11:27 PM (1,023 Views)
Mrbreeze


I searched and did not find anything regarding this, I have always done this and wondered if anyone else does, I also use a one step hotter plug, calls for a BPR6ES and I always use BPR5EY-11, no problems, just thought I'd throw that out there for some feedback..
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perfesser
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Elite Member - Former Metro owner

What is "indexing"?
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Mrbreeze


I mark the ceramic with a sharpie where the ground tip points and I use old plug washers to shim the plug so that it points down to the piston, into the combustion chamber, if necessary.. That way the spark is always firing toward the piston..
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Old Man


What 'gains' have you documented by using 'indexing'?
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Mrbreeze


Well I've never burned any valves... I do know that if I use stock heat range plugs it just runs like I put regular fuel in it, not very zippy..
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Bad Bent
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Facetious Educated Donkey

A little research, at http://www.sr20-forum.com/naturally-aspirated-all-motor/4369-how-index-your-spark-plugs.html there is this pic:

Posted Image Spark plug firing "bubble"

At http://www.hubgarage.com/mygarage/summitracing/blogs/10030 and http://www.hubgarage.com/mygarage/summitracing/blogs/10030 they index the flame toward the valves.

From Hubgarage.com "The technique of indexing a spark plug involves getting the ground strap of the plug properly positioned when the plug is fully seated in the cylinder head. The ideal situation is to have the spark gap facing directly at the intake valve and approaching fuel charge. This increases combustion efficiency and puts the spark directly in the fuel charge path. When left to chance, if the ground strap would end up between the intake charge and the spark gap it blocks the flow, causing unneeded turbulence, and results in a less efficient ignition of the charge. In very high performance racing engines, indexing can also provide additional clearance for high dome pistons."

A little pricey but here are Moroso indexing washers for spark plugs: http://www.ebay.com/search/Moroso+spark+plug+washers

But the Mrbreeze indexing may save G10 valves :dunno

A little more searching and NGK says this:
"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 point 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."


Or a 50hp engine would "be lucky" to get 1hp. :-/ :hmm
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Woodie
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Bad Bent
Jul 27 2014, 02:42 AM
For a 500hp engine, you'd be lucky to get 5hp.
Or a 50hp engine would "be lucky" to get 1hp. :-/ :hmm
Optimistic math. A 50 hp engine would be lucky to get .5 hp.
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