Thread: For Spark plugs fans . Indexing

Love it...

I discovered spark plug indexing years ago, while reading a book on how to get the most out of your Harley-Davidson Sportster engine.

Never got around to doing it, and have enough to work on and maintain without going to this extreme, but interesting theory...

I suspect that in the real world the definable difference between indexed and non indexed spark plugs would be just about zero.

Sound pretty pointless to me. The minor gain (if any) would be the same as the bees knob loss (if any) in compression...

Also the analogy of a bomb in the room... doesn't really work that way.
In this case the entire room is the bomb... if you are in the room you are inside the bomb.
The entire combustion chamber is the bomb. not the end of the spark plug.

Of course this is just my take on it.

Indexing plugs is a part of Blueprinting an engine to achieve maximum efficencey which equals more power, more power than your competitors that don't blueprint means the difference between winning and losing.
Flame travel/flame front is extremely important in HP competition engines, so if you don't think so then you will be among the losers, regards Frank.

The prime benefit is more toward eveness of burning, comparing each cylinder with its mates... and therefore smooothness.
This is supposed to translate to (marginally...) quicker spool-up plus a tad more peak RPM...

Rationale is... the less energy expended in vibration, the more available to the wheels.

Actual figures are a differant story.... might not be clearly felt in general motoring... but the Rover v8 is somewhat lacking in efficiency, so that any and every little helps !:...

I like to look at the spark plug electrode positions and give the same advice I always give.

"This engine would be a lot more efficient if it was setup to run a diesel injector in that hole."

I forgot to use the bathroom before I went out on track so have negated the effects of spark plug indexing.

I classify it in the last 1% of things you should do when you have the previous 99% up scratch, otherwise its just a whole load of mechanical time wasting.

Originally Posted by blue_mini

I forgot to use the bathroom before I went out on track so have negated the effects of spark plug indexing.

I classify it in the last 1% of things you should do when you have the previous 99% up scratch, otherwise its just a whole load of mechanical time wasting.

If you race a category like Formula Ford, Formula 3, V8 Taxi Cars, etc you use every last little tweak you can, it's all too tight and the competition too fierce not to as you've already covered the previous 99%.
Everyone in categories like that are dead serious and go all out.
It's Sheep Stations at 20 paces, even in State Championships.
If you don't want to do that too you choose another category.
It's not good or bad, just the way it is.

On a road car only the truly anal would do it......

But then, the sort of person that indexes plugs on race and road engines possibly does it on chainsaws along with modified earth electrodes and possibly modifies chainsaws including carbies too.

Modified (and indexed) chainsaw plug.



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A 17% increase in cross sectional area without having to bore the venturi = more airflow/power without losing depression across the venturi = no loss of torque.





Must. Get. A. Life.