Side gapped spark plugs

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Side gapped spark plugs

Postby L67PSI » Sat Oct 21, 2017 11:09 pm

Hi all,

I saw the idea online of side gapped spark plugs and thought I'd give it a go on my VT supercharged L67. Today I removed the plugs to fit new ones, anyway here is a pic of one that I removed. It's approx 6 months old and gapped to 1.1mm on a 45 degree angle from the center electrode to ground strap. I noticed that the center electrode has slowly started to wear on the edge. With these installed it ran smooth and no issues under boost.

Has anyone else tried this? Also any comments on the plugs condition?

Side_gapped_NGK.jpg
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Re: Side gapped spark plugs

Postby The1 » Sun Oct 22, 2017 7:02 am

Youl find the plug centre and strap will wear quickly, performance won't be any better only worse as you've reduced the surface area where spark can arc from. Obviously your coils are upto the task if you've not seen any more knock introduced, from testing I've done the only better design that creates more consistent spark is the v groove, which adds slightly more surface area again

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Re: Side gapped spark plugs

Postby delcowizzid » Sun Oct 22, 2017 7:25 am

Yeah one would expect side gapped to be going bad in a shorter amount of time with only a third of the centre electrode surface used and a third of the ground electrode surface used to produce spark probably clever marketing by manufacturer really lol
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Re: Side gapped spark plugs

Postby festy » Wed Jan 24, 2018 11:51 am

My alfas and bike all use OEM 'side gapped' plugs, although I usually run single ground plugs in the alfas because the OEMs are about $30 each :oops:

Advantages are that you don't have to index the plugs on hot motors, better plug life and less sensitive to voltage (more forgiving on gap).
You'd lose most of the advantages with a single ground side gapped plug though.

These two plugs have plenty of miles on them, but wear looks minimal and even.
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NGK-R.jpg
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Re: Side gapped spark plugs

Postby vlad01 » Wed Jan 24, 2018 12:26 pm

I've used those multi electrode bosch ones before. They were shite
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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Re: Side gapped spark plugs

Postby delcowizzid » Wed Jan 24, 2018 12:58 pm

Nothing beats a standard copper plug lol
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Re: Side gapped spark plugs

Postby vlad01 » Wed Jan 24, 2018 1:10 pm

genuine Nippon denso GM plugs ftw!
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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Re: Side gapped spark plugs

Postby festy » Wed Jan 24, 2018 2:31 pm

delcowizzid wrote:Nothing beats a standard copper plug lol

Big valves and high lift cams beat them pretty badly in some hemispheric combustion chambers :comp:

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Obviously no one style of plug works best in all engines.

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Re: Side gapped spark plugs

Postby vlad01 » Wed Jan 24, 2018 2:38 pm

Thats the builders fault, not the plug.

I don't see how its possible for the valves to do that, looks like the pistons was contacting the plug.
I'm the director of VSH (Vlad's Spec Holden), because HSV were doing it ass about.

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Re: Side gapped spark plugs

Postby festy » Wed Jan 24, 2018 3:09 pm

No, that's using the wrong length plugs on a well built head.
Trust me, it's a thing.

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