spark plug indexing

[vintage bikeworks]

Did a quick search here for spark plug indexing and didn't see a thread.  Has anyone tried it and noticed any improvement?  I'm getting ready to give it a try. 

[fret not]

Indexing?  How do you mean?

[vintage bikeworks]

Positioning the spark plug so the open end of electrode gap faces the intake valve(s).  In this way, the spark faces the incoming air/fuel mix.  Can be accomplished with special thickness washers under spark plug seat or if you have a selection of plugs, you can try several until you find one that faces the right way when tightened.  Can potentially improve idling and overall performance. 

[The Prophet of Doom]

Be sure to write up how it goes on the XZ. Another must-do for my "all the mods" vision.

[Walt_M.]

Spark plug indexing? I'm not even sure if I have changed the winter air in my tires for summer air. And don't get me started on the muffler bearings.

[Jirik]

I'm hearing for the first time about it. You can use spark plug with more electrods (I don't know, if exists for our XZ).

This kind looks very well: https://www.youtube.com/watch?v=z3jQXl7o_JY

[vintage bikeworks]

Spark plug indexing? I'm not even sure if I have changed the winter air in my tires for summer air. And don't get me started on the muffler bearings.

Ha....!   :)   Ok, look at it this way.  By indexing the plug, you are not shielding the spark (with the side electrode) from the incoming fuel/air mixture.  The racing crowd has been doing this for a long time.

[vintage bikeworks]

Be sure to write up how it goes on the XZ. Another must-do for my "all the mods" vision.

....Will do. 

[QBS]

I am familiar with the concept.  A  two valve, squish design combustion chamber (like many American automotive V8s) benefits the most from the process.  A two valve hemispherical chamber with a centrally placed spark plug (think BMW air head)would benefit as well, but due the centrality of the plug replacement, not as much.

IMHO, our V's, with four valves, a narrow included valve angle, a central plug, and relatively flat chamber might theoretically see some power increase.  But, I'm thinking that in the real world it would be invisible.  One of the major, yet often over looked, advanced design features of the V engine is the very efficient combustion chamber design.  It breathes really well.  As such, to achieve a worthwhile  power increase over stock would require a fairly extreme amount of modification.  And that increase would be most applicable only in highly competitive racing situations.

[fret not]

I'm beginning to suspect that the state of engine tune would need to be rather extreme for this to make an appreciable effect.  I suppose it couldn't hurt. 

[The Prophet of Doom]

Even if it's just 1/2 hp difference, do that 20 times to 20 different components and you've made a decent seat of pants improvement

[Walt_M.]

I do believe the intake valves have been closed for a very long time as the spark occurs on the compression stroke. Spark plug indexing would be more important in older two strokes.

[vintage bikeworks]

Okay...  Indexing the plugs was a fairly straightforward process.  I had 3 different thickness of washers on hand to add under the spark plug sealing washer if needed.  Having an extra 4 new plugs allowed me, by trial and error to find 2 plugs that indexed correctly after being tightened.  This was easier than backing the sealing washer off and placing a shim washer underneath.  There was no "seat of the pants" improvement so...

Maybe the Vision's 4 valve head with centrally located spark plug does not benefit from the indexing.  With my current set-up of hotter dyna coils, better wires and iridium plugs, maybe I'm at peak ignition performance with the engine's present state of tune?  It may be possible someone who has a baseline miles per gal/km may see improved gas mileage after indexing?   I've never recorded gas mileage so have nothing to compare to.  Oh well.  It was little effort and no harm done in trying.