The Ford Barn

[email protected] · 07-18-2012, 09:13 PM

Maybe a HAMB question but let's see what happens.

This spark plug indexing info is in wikipedia and I am curious as to if it actually works with Model A's. Anybody have any knowlege on Model A drivers doing this to tweak that last micro-ounce of performance out of 40 hp?

Indexing spark plugs
A matter of some debate is the "indexing" of plugs upon installation, usually only for high performance or racing applications; this involves installing them so that the open area of the spark gap, not shrouded by the ground electrode, faces the center of the combustion chamber, towards the intake valve, rather than the wall. Some engine tuners believe that this will maximize the exposure of the fuel-air mixture to the spark, also ensuring that every combustion chamber is an even in layout and therefore result in better ignition ; others, however, believe that this is useful only to keep the ground electrode out of the way of the piston in ultra-high-compression engines if clearance is insufficient. In any event, this is accomplished by marking the location of the gap on the outside of the plug, installing it, and noting the direction in which the mark faces; then the plug is removed and additional washers are added so as to change the orientation of the tightened plug. This must be done individually for each plug, as the orientation of the gap with respect to the threads of the shell is random.

Pete · 07-18-2012, 09:26 PM

I never did any dyno pulls on an A/B engine to determine if plug indexing did any good but I did on flathead Ford V8's.
The engine was a 315 ci all out engine on alcohol and made 318 hp.
Plug indexing had NO affect. I tried both conventional electrode and side electrode racing type plugs.

Patrick L. · 07-19-2012, 05:48 AM

I've tried it back years ago on high power V8s,, no difference.. I also years ago made my own 'split-fire' sparklers,, no difference either..

MikeK · 07-19-2012, 09:20 AM

I know you guys are talking about the ground electrode orientation, but I did something else. I have a set of original 3X for my 40B and I loosened the top lock nut for the insulators and rotated the porcelain so the 3X's would all line up. Sure looks nice!! Gave me a real power surge.

Patrick L. · 07-19-2012, 02:26 PM

Boy, when I get that kind of power surge, I hope JoAnn is nearby..

Brian LI · 07-20-2012, 08:48 AM

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I would think that with the amount of turbulence in the incoming charge of a flathead engine that indexing plugs is probably a waste of time.

Kurt in NJ · 07-20-2012, 09:06 AM

The 3X plug is designed so that indexing is not a problem, the ground electrode is off to the side --my top speed when using 3X plugs was 67mph, with other plugs I never could drive over 55 ----but I would say it was the change to a "B" cam more than spark plugs, I just havn't used any other plugs since the cam change

jrapose · 07-20-2012, 10:49 AM

Mike, You made me smile...and these days that is a hard thing to do....thanks...I enjoyed your comment...

Joel
Chester Calif. (working too hard)

07-18-2012, 09:13 PM	#1
[email protected] Senior Member Join Date: Aug 2011 Location: Illinois Posts: 736	Indexing of spark plugs on your Model A Maybe a HAMB question but let's see what happens. This spark plug indexing info is in wikipedia and I am curious as to if it actually works with Model A's. Anybody have any knowlege on Model A drivers doing this to tweak that last micro-ounce of performance out of 40 hp? Indexing spark plugs A matter of some debate is the "indexing" of plugs upon installation, usually only for high performance or racing applications; this involves installing them so that the open area of the spark gap, not shrouded by the ground electrode, faces the center of the combustion chamber, towards the intake valve, rather than the wall. Some engine tuners believe that this will maximize the exposure of the fuel-air mixture to the spark, also ensuring that every combustion chamber is an even in layout and therefore result in better ignition ; others, however, believe that this is useful only to keep the ground electrode out of the way of the piston in ultra-high-compression engines if clearance is insufficient. In any event, this is accomplished by marking the location of the gap on the outside of the plug, installing it, and noting the direction in which the mark faces; then the plug is removed and additional washers are added so as to change the orientation of the tightened plug. This must be done individually for each plug, as the orientation of the gap with respect to the threads of the shell is random.

07-18-2012, 09:26 PM	#2
Pete BANNED Join Date: May 2010 Location: Wa. Posts: 5,423	Re: Indexing of spark plugs on your Model A I never did any dyno pulls on an A/B engine to determine if plug indexing did any good but I did on flathead Ford V8's. The engine was a 315 ci all out engine on alcohol and made 318 hp. Plug indexing had NO affect. I tried both conventional electrode and side electrode racing type plugs.

07-19-2012, 05:48 AM	#3
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Indexing of spark plugs on your Model A I've tried it back years ago on high power V8s,, no difference.. I also years ago made my own 'split-fire' sparklers,, no difference either..

07-19-2012, 09:20 AM	#4
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: Indexing of spark plugs on your Model A I know you guys are talking about the ground electrode orientation, but I did something else. I have a set of original 3X for my 40B and I loosened the top lock nut for the insulators and rotated the porcelain so the 3X's would all line up. Sure looks nice!! Gave me a real power surge.

07-19-2012, 02:26 PM	#5
Patrick L. Senior Member Join Date: May 2010 Location: Largo Florida Posts: 7,225	Re: Indexing of spark plugs on your Model A Boy, when I get that kind of power surge, I hope JoAnn is nearby..

07-20-2012, 08:48 AM	#6
Brian LI Member Join Date: May 2010 Location: Long Island "The weiner of New York State" Posts: 41	Re: Indexing of spark plugs on your Model A Sponsored Links (Register now to hide all advertisements) I would think that with the amount of turbulence in the incoming charge of a flathead engine that indexing plugs is probably a waste of time.

07-20-2012, 09:06 AM	#7
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,182	Re: Indexing of spark plugs on your Model A The 3X plug is designed so that indexing is not a problem, the ground electrode is off to the side --my top speed when using 3X plugs was 67mph, with other plugs I never could drive over 55 ----but I would say it was the change to a "B" cam more than spark plugs, I just havn't used any other plugs since the cam change

07-20-2012, 10:49 AM	#8
jrapose Senior Member Join Date: Jan 2012 Posts: 249	Re: Indexing of spark plugs on your Model A Mike, You made me smile...and these days that is a hard thing to do....thanks...I enjoyed your comment... Joel Chester Calif. (working too hard)