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setting plug gap on cut back ground electrodes

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Old Oct 2, 2008 | 08:31 PM
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Default setting plug gap on cut back ground electrodes

I have a set of Autolite AR 3910's, the ones with the cut back ground electrode, how are you setting the plug gap on these?
Say your setting it to .040", are you measuring the distance between the edge of the ground electorde to the edge of the center electrode ?

cheers
Nick
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Old Oct 2, 2008 | 09:47 PM
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Hi Nick,

electricity like to go the easy way- set the gap at the closest point, be it the side or the end of the electrode.

Just for info, I used a couple of sets of the Autolite AR plugs. Made the car hard to start, (very easy to flood it), and didn't last for long. It was running very rough and was missing at idle. New set of AR's fixed it, but wasn't too long before it was at it again. And they were also about 2x more $. I went back to plain old Autolite plugs and no more problems.

I'll admit up front that with the rectangle port heads and the ZL-1 cam and 12.5 compression, there are lots of reasons it gets cranky. But it sure is easier to start with standard full electroe plugs and they DO seem to last longer.
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Old Oct 3, 2008 | 08:51 AM
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I will set up the gap to .040 between the edge of the electrodes and see what they do.
I have some Autolite 3923's and 3924's here aswell I can use.

Nick
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Old Oct 4, 2008 | 09:16 AM
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Originally Posted by lvrpool32
I will set up the gap to .040 between the edge of the electrodes and see what they do.
I have some Autolite 3923's and 3924's here aswell I can use.

Nick
.035", not .040"
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Old Oct 4, 2008 | 10:03 AM
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Depending on the ignition type it is easy to run wider gaps. between .040 and .050 is about is low as I would go with aftermarket electronics
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Old Oct 4, 2008 | 03:39 PM
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[QUOTE=gkull; between .040 and .050 is about is low as I would go with aftermarket electronics[/QUOTE]


Like MSD? Their information doesn't give a gap measurement, it just says change it in increments of .005" - .010".

I'm running a blown big block with MSD. Should I start around .050"?

Thank you
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Old Oct 4, 2008 | 05:10 PM
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Originally Posted by FB007
.035", not .040"
I don't use those plugs, but my gap is .060, unblown big block, with MSD ignition
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Old Oct 4, 2008 | 05:19 PM
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Originally Posted by lvrpool32
I have a set of Autolite AR 3910's, the ones with the cut back ground electrode, how are you setting the plug gap on these?
Say your setting it to .040", are you measuring the distance between the edge of the ground electorde to the edge of the center electrode ?

cheers
Nick
I didn"t think you were supposed to set the gap on those cut back plugs???????
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Old Oct 4, 2008 | 05:41 PM
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Originally Posted by BigBlockTank
I don't use those plugs, but my gap is .060, unblown big block, with MSD ignition
Thank you! Mind if I ask which plugs you do use?
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Old Oct 4, 2008 | 07:08 PM
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.035 with Autolites and .035 with Delphi plugs and an MSD ignition.....

Last edited by redvetracr; Oct 4, 2008 at 07:11 PM.
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