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Old 06-30-2015, 09:10 AM   #1
Joshontech
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Spark plug gap question

I just put sparkplugs in my lumina ls 3100 engine. I know the recomended gap is .060 but I was wondering if putting it at .055 or .050 would hurt? I have the NGK G-Power platinum tip copper core plugs in it now. I know I did some research on the topic and say one thing that said gapping your plugs smaller may improve response time and smooth out your idle. I know it's easier on the ignition system to gap them smaller but I didn't know if it would do any damage to the engine. Thanks for your help on this guy's.
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Old 06-30-2015, 11:40 AM   #2
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Re: Spark plug gap question

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Originally Posted by Joshontech View Post
I just put sparkplugs in my lumina ls 3100 engine. I know the recomended gap is .060 but I was wondering if putting it at .055 or .050 would hurt? I have the NGK G-Power platinum tip copper core plugs in it now. I know I did some research on the topic and say one thing that said gapping your plugs smaller may improve response time and smooth out your idle. I know it's easier on the ignition system to gap them smaller but I didn't know if it would do any damage to the engine. Thanks for your help on this guy's.
I can't see why it would damage the engine to reduce the spark plug gap. But I would only put the AC Delco plug that is recommended by GM in there. And I would also gap them the way GM recommends.
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Old 06-30-2015, 12:36 PM   #3
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Re: Spark plug gap question

Fatter spark is more efficient, leave the .060 gap.
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Old 06-30-2015, 01:08 PM   #4
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Re: Spark plug gap question

I did replace the original spark plugs with acdelco platinum plugs advanced auto said they were the oem plugs that came installed in the engine. After about 30k miles I noticed the engine running rough and starting hard so I thought it was time to check the spark plugs. When I took the easy side 3 spark plugs out they were extremely yellowed and had rust colored deposits on the ground. I looked online and found out that the plugs where overheating henchmen the yellowing and rust colored deposits. I went to get the same plugs and they do not make them anymore not the exact same ones and also the acdelco all have high heat ranges so I figured that's why they overheated. My dad always uses the NGK plugs and they last forever and the g-power ones have a heat range a lot lower than the acdelco so I thought I would try them. And thanks for letting me know about the spark gap I just wanted to know if what they said on the one website was true.
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Old 07-01-2015, 07:04 AM   #5
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Re: Spark plug gap question

FWIW, original equipment plugs for ACDelco have been manufactured by Denso and NGK for years. Some original plugs pulled from engines have been stamped "AC-Delco by NGK" and "Denso" very clearly. Back in the '80s-'90s I worked at a Textron division which headed blank shells for AC-Delco by the millions, among many other OEM parts (valve retainers, crank and rod cap bolts, rocker studs, all sorts of ball joints, starter gears, etc.), and I know that wasn't an isolated incident. GM outsources a lot of the parts used in their products.

What is most important is using a plug with the proper heat range and reach.
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Old 07-01-2015, 08:09 AM   #6
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Re: Spark plug gap question

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FWIW, original equipment plugs for ACDelco have been manufactured by Denso and NGK for years. Some original plugs pulled from engines have been stamped "AC-Delco by NGK" and "Denso" very clearly. Back in the '80s-'90s I worked at a Textron division which headed blank shells for AC-Delco by the millions, among many other OEM parts (valve retainers, crank and rod cap bolts, rocker studs, all sorts of ball joints, starter gears, etc.), and I know that wasn't an isolated incident. GM outsources a lot of the parts used in their products.

What is most important is using a plug with the proper heat range and reach.
Wow that's crazy and I believe it too. What would be the proper heat range for my gm 3100 engine?
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Old 07-01-2015, 05:49 PM   #7
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Re: Spark plug gap question

First Guess: The deposits you saw were from the gasoline used, not from "overheating".

Second Guess: A straight interchange from AC to NGK won't hurt a thing. Going colder may--or may not--promote fouling.

Third Guess: .060 gap is just fine, but I'd consider smaller. Excess gap promotes misfire if the insulation on the secondary circuit has flaws. I'm pretty sure my 3.4L DOHC uses a .045 or .040 gap.
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Old 07-02-2015, 06:57 PM   #8
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Re: Spark plug gap question

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First Guess: The deposits you saw were from the gasoline used, not from "overheating".

Second Guess: A straight interchange from AC to NGK won't hurt a thing. Going colder may--or may not--promote fouling.

Third Guess: .060 gap is just fine, but I'd consider smaller. Excess gap promotes misfire if the insulation on the secondary circuit has flaws. I'm pretty sure my 3.4L DOHC uses a .045 or .040 gap.
That's what I thought as well because I have used injector cleaner and such but when researching online I found many instances where over heated plugs looked just like the ones I took out of my car.

I really don't understand why the manufacturer puts the recomended gap size so far apart on my car but I know that supercharged medals of my car and yes I have seen some crazy people supercharg the gm 3100 Gen 2 and they all said they use .045 gap.
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