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Spark Plug Indexing....
https://slantsix.org/forum/viewtopic.php?t=15578		 Page 1 of 1
Author:  emsvitil [ Sat Dec 31, 2005 7:50 pm ]
Post subject:  Spark Plug Indexing....
As anyone done it?

Notice any differences?

Does it matter with the extended tip plugs?
Author:  Eric W [ Sat Dec 31, 2005 9:49 pm ]
Post subject: 
Drive a race car? No? Don't waist your time. Back-cutting to unshroud the spark would be better.
Author:  emsvitil [ Sat Dec 31, 2005 10:00 pm ]
Post subject: 
Quote:
Back-cutting to unshroud the spark would be better.

Not quite sure of what you mean..........
Author:  emsvitil [ Sun Jan 01, 2006 12:22 pm ]
Post subject:  cutback
Ok I think I've got it.........

I was going........ 'what does back-cutting a valve have to do with a spark plug'........


You mean cutback the plug........ :idea:

Got a dremel, so that's easy. I'd do either a single cut and have the ground electrode protrude over the center electrode by about 1/3.

Or a tapered cut (3 dremel cuts) and have the ground electrode over the center by about 1/2.

Then have the gap at about .042 instead of the .045 I'd run without cutting the electrode (there's less electrode to wear away, so just a little tighter to compensate)


From looking at the combustion chamber

Image

I'd think the ground electrode should be somewhere in the semi-circle that's on the head (roughly a 90 degree wedge as good).

And the place to avoid having the ground electrode would be directly opposite the good area (the 90 degree wedge next to the piston)

With 6 plugs and 6 combustion chambers I'd think you should be able to at least avoid the bad area.....
Author:  Eric W [ Sun Jan 01, 2006 7:00 pm ]
Post subject:  Re: cutback
Quote:
You mean cutback the plug........ :idea:

Got a dremel, so that's easy. I'd do either a single cut and have the ground electrode protrude over the center electrode by about 1/3.
Yes, thats what I ment. :oops:
Author:  64ragtop [ Mon Jan 02, 2006 11:48 am ]
Post subject:  Plug indexing?
I've read comments about spark plug indexing, and this thread confirms what I thought I knew about it. Mainly that I don't need to worry about it unless I build a race motor where every little bit counts.
BUT, curious ol' cuss that I am, I read enough to get confused, so I'd like some clarification.

EMSVITIL mentioned a good area for the electrode being "somewhere in the semi-circle that's on the head (roughly a 90 degree wedge as good).

And the place to avoid having the ground electrode would be directly opposite the good area (the 90 degree wedge next to the piston) "

Looking at his photo of the chamber, I guess his "good" area is the raised area between the valve seats. Though it seems to me that would shroud the spark to some infinitesimal degree.

The part of that post that REALLY left me scratching my head was about cutting the electrode with a Dremel tool. "I'd do either a single cut and have the ground electrode protrude over the center electrode by about 1/3.

Or a tapered cut (3 dremel cuts) and have the ground electrode over the center by about 1/2.

Then have the gap at about .042 instead of the .045 I'd run without cutting the electrode (there's less electrode to wear away, so just a little tighter to compensate)

I'd like to SEE that, as I can't seem to visualize it. Got pics???
Author:  emsvitil [ Mon Jan 02, 2006 1:37 pm ]
Post subject:  Re: Plug indexing?
Quote:
Looking at his photo of the chamber, I guess his "good" area is the raised area between the valve seats. Though it seems to me that would shroud the spark to some infinitesimal degree.

The part of that post that REALLY left me scratching my head was about cutting the electrode with a Dremel tool. "I'd do either a single cut and have the ground electrode protrude over the center electrode by about 1/3.

Or a tapered cut (3 dremel cuts) and have the ground electrode over the center by about 1/2.

Then have the gap at about .042 instead of the .045 I'd run without cutting the electrode (there's less electrode to wear away, so just a little tighter to compensate)

I'd like to SEE that, as I can't seem to visualize it. Got pics???

With the ground electrode in the semi-circular area of the head, I think this would minimize shrouding (at least on a slant-6 head)

no-pics, haven't done it yet.........

How about ascii art


normal:

===== |
______|


cutback:

===== .
______|


the end of the ground electrode would either only be over 1/3 of the center electrode or 1/2.

Top view of ground electrode
Single cut: (ignore '.'s used for spacing)

|....|
|__|


tapered cut:

.|....|
..\_/
Author:  emsvitil [ Mon Jan 02, 2006 1:41 pm ]
Post subject:  Picture
Here's a pic

http://www.geocities.com/jgkov/CutPlugs.html


That's about 1/6 over center electrode........
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