Spark Plug 101

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Nov 16, 2003 | 05:43 PM

#16

MAHinton

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Joined: Jan 2002

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From: Kansas

I have a stock ignition in both trucks (the "breakerless" kind), with stock coil, and stock wires. The underhood sticker has the gap listed at 0.052 to 0.056, so I run 0.054 on regular Motorcraft plugs (don't know the number for sure, just the equivalent of what the Hayne's manual has listed). Granted, I don't drive that much, 3,000 miles a year total on both trucks, and almost all city. But I've not had any problems with wires, caps, rotors, or coils burning out prematurely. Most people have been rather shocked when I mention the plug gap. But that's what the sticker says, that's what any manual says to reference, and I don't have any other point of comparison.

Matt

Nov 17, 2003 | 08:36 AM

#17

71FoMoCo

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Joined: Feb 2003

Posts: 395

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From: South Carolina

Alright, somebody edjumacate me here. Does more gap make more power? I've got full MSD ignition/Dizzy with MSD 8.5mm wires, Autolite plugs. How much gap is optimal for max power?

Nov 19, 2003 | 10:40 AM

#18

71FoMoCo

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From: South Carolina

...

Nov 22, 2003 | 10:11 AM

#19

71FoMoCo

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From: South Carolina

...

Nov 23, 2003 | 06:54 PM

#20

Andysutt

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Joined: Jan 2003

Posts: 3,775

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From: Conway Arkansas

I have a duraspark ignition, ford electronic dizzy, MSD Blaster 3 coil, 8mm Accel plug wires...
and I run Autolite 45s gaped to .50
Runs very good

Nov 23, 2003 | 06:54 PM

#21

Andysutt

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Joined: Jan 2003

Posts: 3,775

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From: Conway Arkansas

I have a duraspark ignition, ford electronic dizzy, MSD Blaster 3 coil, 8mm Accel plug wires...
and I run Autolite 45s gaped to .50
Runs very good

Nov 23, 2003 | 07:12 PM

#22

proeliator

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Joined: Sep 2000

Posts: 8,238

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From: Oregon

I just looked back in on this thread '71, so I'll take a stab at your question. Basically, you want as much of the spark kernel exposed to the combustion chamber...more spark equals better combustion equals, yes, more power. This is why some old racers used to "sidegap" their plugs. Some still do, and many index their plugs. Its the theory behind splitfires...and while I don't use them and everybody swears they don't work I've also seen two different FE's pick up some minimal horse on the dyno by doing nothing but switching over to the SF. Its also why those of us who can run a bigger gap do; you get more of a spark to light the candle. Now, many would argue that anything above a .060 gap does not yield any better results. I don't know that for a fact, but I do know that your plugs and wires don't last as long when they've got a big gap to leap. I usually run anywhere between a .050-.060 gap on mine. I usually advise to run somewhere in that range if you run top notch ignition components and have a hot electric ignition. Hope that helped.