Spark plug gap
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Joined: Jun 2007
Posts: 31,070
Likes: 566
I didn’t bother to read all the post, but yeah there is no rule on what the right spark plug gap is, its different for what ever the demands are. Run as large a gap you can get away with, without getting spark blow out, that’s it. Larger gap is always best.
Joined: Aug 2016
Posts: 2,767
Likes: 234
From: In BOOST
I read a workshop manual for a different car state "do not gap used spark plugs" but when searching online even NGK has not said that you should never re-gap a used spark plug. Anyone done this with success or is it always best to buy new plugs and gap those?
Joined: Aug 2012
Posts: 8,724
Likes: 1,830
How used we talkin?
I wouldn't regap plugs near end of life. If its apart, smarter just replace. Last think you want is weaken tip, breaks off inside cylinder during use.
But used but still fresh plugs, I wouldn't hesitate.
Scenario of, say, regapping half used plugs seems rare. If you're adding FI to car that didn't have before, you're likely changing plugs heat range. So plugs gonna be fresh.
Maybe if you're making a change in boost that necessitates gap change, but not heat range change, after plugs been installed for a while?
I wouldn't regap plugs near end of life. If its apart, smarter just replace. Last think you want is weaken tip, breaks off inside cylinder during use.
But used but still fresh plugs, I wouldn't hesitate.
Scenario of, say, regapping half used plugs seems rare. If you're adding FI to car that didn't have before, you're likely changing plugs heat range. So plugs gonna be fresh.
Maybe if you're making a change in boost that necessitates gap change, but not heat range change, after plugs been installed for a while?
Joined: Aug 2006
Posts: 5,586
Likes: 65
From: New England
Successfully re-gapped old Iridium plugs multiple times.
Joined: Aug 2016
Posts: 2,767
Likes: 234
From: In BOOST
How used we talkin?
I wouldn't regap plugs near end of life. If its apart, smarter just replace. Last think you want is weaken tip, breaks off inside cylinder during use.
But used but still fresh plugs, I wouldn't hesitate.
Scenario of, say, regapping half used plugs seems rare. If you're adding FI to car that didn't have before, you're likely changing plugs heat range. So plugs gonna be fresh.
Maybe if you're making a change in boost that necessitates gap change, but not heat range change, after plugs been installed for a while?
I wouldn't regap plugs near end of life. If its apart, smarter just replace. Last think you want is weaken tip, breaks off inside cylinder during use.
But used but still fresh plugs, I wouldn't hesitate.
Scenario of, say, regapping half used plugs seems rare. If you're adding FI to car that didn't have before, you're likely changing plugs heat range. So plugs gonna be fresh.
Maybe if you're making a change in boost that necessitates gap change, but not heat range change, after plugs been installed for a while?
That's what scared me - the possibility of the ground strap breaking in use. Definitely don't want that. Apparently you "shouldn't gap a plug more than 3 times..." according to various sources on the Net.
Joined: Aug 2006
Posts: 5,586
Likes: 65
From: New England
.24 to .28 
You can reference this for S2K gap guide:
https://www.scienceofspeed.com/index...ark-plugs.html
You can reference this for max gap adjustment allowed by NGK:
"NGK doesn't recommend adjusting the plug gap more than .008" in either direction"
https://www.ngk.com/proper-ngk-gapping-instructions
You can reference this for S2K gap guide:
https://www.scienceofspeed.com/index...ark-plugs.html
You can reference this for max gap adjustment allowed by NGK:
"NGK doesn't recommend adjusting the plug gap more than .008" in either direction"
https://www.ngk.com/proper-ngk-gapping-instructions
Joined: Aug 2016
Posts: 2,767
Likes: 234
From: In BOOST
.24 to .28
You can reference this for S2K gap guide:
https://www.scienceofspeed.com/index...ark-plugs.html
You can reference this for max gap adjustment allowed by NGK:
"NGK doesn't recommend adjusting the plug gap more than .008" in either direction"
https://www.ngk.com/proper-ngk-gapping-instructions
You can reference this for S2K gap guide:
https://www.scienceofspeed.com/index...ark-plugs.html
You can reference this for max gap adjustment allowed by NGK:
"NGK doesn't recommend adjusting the plug gap more than .008" in either direction"
https://www.ngk.com/proper-ngk-gapping-instructions
She seems to like it just fine. 10-11 pounds of boost on pump gas, 15 degrees timing. Reason why I gapped these new plugs is because I've been chasing down a random cutout at WOT in boost around 7 to 8 grand. Doesn't happen all the time but pretty much happens at least once when I do some pulls and it's so strange.
Thanks for the links