Plug gap with Accel HEI
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
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From: WV
Plug gap with Accel HEI
Could anyone tell me what the plug gap is when using the Accel HEI high output coil? I have heard that you use a wider gap than .035 when using this coil, but it was on the car when I got it and I have no instruction sheet.I have a stock 89. Thanks WW
Last edited by WW7; Nov 18, 2007 at 04:16 PM.
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Use the same gap as stock .035. The ACCEL HEI coil really doesn't put out a lot more voltage than the stock GM coil. With a stock motor, you may not even see a lot of improvement with the ACCEL coil.
Instructor
Joined: Jul 2007
Posts: 222
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From: Toronto(Don Mills) Ontario
I installed the Accel HEI coil, plus their HEI D.-Module, in my 86, back in 1990. Also Taylor 8 mm plug wires. Gapped a new set of plugs(NGK, as I recall) to .040" ! Have had no problems since, and continue to gap new plugs at the same .040"
Pro
Joined: Oct 2004
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From: Clarksville Tennessee
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Voltage is determined by the plug gap and the cylinder pressure, not the distributor contents. Opening up the gap will require a larger voltage to jump the gap. This will shorten the spark duration. (The NO Free Lunch rule.) If you truly have an upgraded ignition system (meaning more energy, not voltage, contained in the coil) then this will allow you to increase the gap size (generally a good thing) while not necessarily shortening the spark duration.
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
gap
the emissions sticker on most cars should give the plug gap. I gap mine with a pertronix flamethrower coil at .045. I am using splitfire triple platinum plugs, and pull them every 10,000 miles, and they just seem to be happy in there. nice n clean
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by c4cruiser
Use the same gap as stock .035. The ACCEL HEI coil really doesn't put out a lot more voltage than the stock GM coil. With a stock motor, you may not even see a lot of improvement with the ACCEL coil.
With the same ignition system, the spec for my plug gap is .045". I believe in some older stock HEI equipped GM cars the spec was .060". There is a lot of room for experimentation in plug gaps, especially with the relatively powerful HEI ignition system. When you start to experience misfires, stop increasing the gap and back off to where it didn't.
RACE ON!!!
Clarification: The same ignition system, minus the unnecessary Accel coil. In other words a stock HEI.
Last edited by CFI-EFI; Nov 19, 2007 at 11:27 AM. Reason: Clarification
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Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by coupeguy2001
I am using splitfire triple platinum plugs, and pull them every 10,000 miles, and they just seem to be happy in there. nice n clean
RACE ON!!!
Melting Slicks
Joined: Sep 2003
Posts: 3,326
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From: I live at www.domesticlugnuts.com I sleep in PA
Since I change my plugs every 10k, I just use the Autolite copper plugs. I didn't see any performance or mpg difference with the platinum plugs.
Pro
Joined: May 2003
Posts: 682
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From: Annapolis MD
if you want to get the full benefit of the plug and add a few extra hp gap at .047 to .050 and index the plug with the open face towards the exhaust valve. draw a line on the sharpie to know you are opening the face to the exhaust valve.
Racer
Joined: Oct 2004
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From: Mukilteo Washington
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by 77 vette
I would think that he checks, cleans and re-installs them again.
RACE ON!!!
Large Impressive Member
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Voltage is determined by the plug gap and the cylinder pressure, not the distributor contents. Opening up the gap will require a larger voltage to jump the gap. This will shorten the spark duration. (The NO Free Lunch rule.) If you truly have an upgraded ignition system (meaning more energy, not voltage, contained in the coil) then this will allow you to increase the gap size (generally a good thing) while not necessarily shortening the spark duration.
