Changing spark plug gap.

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LRiddle
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Changing spark plug gap.

Postby LRiddle » Thu Aug 17, 2017 7:40 pm

I just added the final piece to my ignition system upgrade/rehab. Over the last few months I've installed new champion d21 plugs, new wires from tm tractor, new cap and rotor, pertronix electronic ignition and today I put on the perteonix flame thrower coil. Most of the work wasn't necessary but things I wanted to do for reliability and peace of mind.

So the question is: Can I open up the plug gap some with the hotter plugs and coil? My thinking is higher voltage can jump a larger gap, creating a longer, hotter spark and burning more fuel more efficiently. I believe the manual says to set gap at .023. Any thoughts or suggestions?
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Re: Changing spark plug gap.

Postby Jim Becker » Thu Aug 17, 2017 8:58 pm

You can go some but I wouldn't open it up much. The more voltage it takes to fire a plug, the bigger the chance it will jump somewhere else (like maybe inside the distributor).

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Re: Changing spark plug gap.

Postby Gary Dotson » Fri Aug 18, 2017 7:21 am

The Pertronix instructions say that if you want, you can open the gap to .035. Personally, I haven't bothered to do so but the next time I pull the plugs I probably will.

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Re: Changing spark plug gap.

Postby inairam » Fri Aug 18, 2017 8:13 am

I went to .030-.032 spark plug gaps on two Pertonix units. Both easy starts.
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LRiddle
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Re: Changing spark plug gap.

Postby LRiddle » Fri Aug 18, 2017 11:57 am

Thanks for the input guys. I think I'll open them up to .032ish to start and maybe go from there.
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Re: Changing spark plug gap.

Postby Rjpoog1989 » Fri Aug 18, 2017 2:42 pm

This may be a really stupid question, but how do you change the gap of a spark plug? I know you need a feeler gauge to measure it, that's about it. I've been running my pertronix with d-21 plugs at whatever gap they had out of the box.
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LRiddle
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Dozer blade

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Rotary Plow
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Re: Changing spark plug gap.

Postby LRiddle » Fri Aug 18, 2017 2:57 pm

Either a feeler gauge or spark plug gap guage. Put the gauge in between the elctrodes and bend the side, or ground, electrode either closer to or further from the center electrode until the gauge fits snuggly between them.
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Re: Changing spark plug gap.

Postby Eugene » Fri Aug 18, 2017 2:58 pm

Search the internet for "spark plug gapping tool". Whole bunch of different styles. Most have some sort of handle with slots. Simply place the plug's electrode in the slot and bend to open or close the gap.
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LRiddle
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Re: Changing spark plug gap.

Postby LRiddle » Fri Aug 18, 2017 3:02 pm

Here is a picture of one type of gauge in use. Then you simply open or close that gap until it fits right. You should check plug gap before installing them. Even out of the box they could be set different than your application calls for or perhaps from bouncing around during shipping.
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Luke Riddle
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Re: Changing spark plug gap.

Postby tnestell » Fri Aug 18, 2017 3:39 pm

I gapped my plugs at .035 when I installed a pertronix ignition along with their 40,000 volt coil. That was in 2006 and I haven't touched then since. I do use the Cub and have about 260 hours since then.

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Re: Changing spark plug gap.

Postby Puffie40 » Sun Aug 20, 2017 11:48 pm

Rjpoog1989 wrote:This may be a really stupid question, but how do you change the gap of a spark plug? I know you need a feeler gauge to measure it, that's about it. I've been running my pertronix with d-21 plugs at whatever gap they had out of the box.

if you are asking about how to change the gap after measuring, its done by gently bending the outer electrode. a small flat-blade screwdriver can be used to pry it up (Some gap gauges have a hole or notch that can be hooked on and worked like a bottle opener) or press the electrode against a hard surface to bend it down. Just be careful not to mess with the center or inner electrode. it cannot be adjusted and if the insulation chips or cracks, its hooped.

adjusting the gap is a pretty simple process once you get the hang of it. I like to keep my gaps below 0.25, but I'm also running magnetos as well.

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Re: Changing spark plug gap.

Postby Rjpoog1989 » Mon Aug 21, 2017 7:30 pm

Thanks for the replies all! I'm going to have to get a gap gauge and see where mine are at.
1948 McCormick Deering Farmall Cub: Woods 59 mower
1994 Toro Wheel Horse 312-8: 42" rear discharge deck
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