Spark plug indexing

[cmontana]

Is anyone taking the time to index their spark plugs? If so, in what direction do you face the gap? Do you perceive a noticeable improvement in performance?

 

[Lawn Masters]

I just put it in till its tight enough that it wont come out or cause the saw to lose compression. how do you know when the gap is facing the piston anyway?

 

[CNYCountry]

I've heard of this but I thought it was more important in overhead valve engines or something, the gap faces the center of the combustion chamber so the negative electrode doesn't divert the newly started flame front.

I guess they use different thickness washers under the plug so when it screws in tight the negative electrode winds up in the orientation you want it.

From what I understand it makes very little difference if at all...

 

[klickitatsacket]

Yes on certain saws I will index my plugs. Some times it takes 8 or 10 plugs to find one that is right. I face the open gap toward the piston. I have been told both that it helps and that it makes no differance. I figure if the least it does is nothing then I have only to gain. I feel it actually does help. I find that there tends to be less build up on an indexed plug.

 

[PWB]

I just put it in till its tight enough that it wont come out or cause the saw to lose compression. how do you know when the gap is facing the piston anyway?

Just use a magic marker to put a mark on the plug where the gap is. Like the man said, you might go through a whole handful of plugs to find one that lines up where you want it. Never thought about doing this on saws, know several guys with drag cars that do it as standard practice, never tried it myself.

 

[CNYCountry]

Just use a magic marker to put a mark on the plug where the gap is. Like the man said, you might go through a whole handful of plugs to find one that lines up where you want it. Never thought about doing this on saws, know several guys with drag cars that do it as standard practice, never tried it myself.

I've heard of guys using washers under the plug of different thicknesses also but I always wondered how that would seal, and that obviously won't work with a tapered seat plug.

 

[ozflea]

Yes indexing spark plugs on 4 stroke engines is important just place a make on the outside of the plug opposite the plug gap and using plug washers get the plug gap alined to point to the inlet valve when tightened.

But not to sure if this works on 2 strokes.

Mc Bob.

 

[GOBRDGO]

copper indexing washers:
Moroso part # 71900 for 14 mm taper seat plugs
part #71910 for flat seat plugs
On a four stroke the trick is to make the gap face the center of the cylinder towards the exhaust valve. Never double up washers! This may be a trick that moves mountains on some engines or not at all on others. I'm not qualified to comment on a two stroke.

 

[GOBRDGO]

Bob just quoting a book, maybe it works different down under.

 

[ErrolC]

I came upon the subject quite a few years ago that gave some specific test results..I'll try and dig it up..the principle isn't so much to direct any flame front or the like..rather to take advantage of a sort of flushing effect the charge swirl has on,
1:most effectively cooling the plug insulator and central electrode, better managing the highs and lows (light load/heavy load) of the plugs working range
2:ensuring a clean exh gas free environment around the electrode which affects the opposing faces of the earth arm and central electrode and the ability to consistantly ionise the gap between and create the best possible spark.

There is another tip to better plug performance....proper gapping (of course), squaring the earth arm so it is parallel with the central electrode face.. and rounding the earth electrode arm tip (so the end isn't square as you look into the insulator, not side on).

This last point has definite benefits..as the electromagnetic charge builds in the central electrode, a counter field effect builds in the earth electrode arm, but it builds most, & more quickly at the corners (points) of the square end and causes the electrical arch to begin leaping prematurely, and only to the points causing a weaker (yet slightly longer duration) and less effective spark.

 

[Fish]

I index mine toward the holy city of Mecca, but of course, as anyone knows, that below the equator, you must do the opposite..........................................................................................






Also, with a tiny drill, I make my plugs hollow-pointed {splitfire of course}.......................................




But I am not qualified to comment at all...................







But I digress.................................