Spark Plug Gap - Ford Mustang Forum

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post #1 of 9 (permalink) Old 09-20-2001
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Spark Plug Gap

Hey guys... I'm putting in new plugs and I'm wondering what I should gap them at. The factory recommendations are .048-.052... Can I gap them any bigger than that for better performance? Open to any advice, thanks.

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post #2 of 9 (permalink) Old 09-20-2001
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Re: Spark Plug Gap

Gap them at the factory specs, unless you have a power adder like a blower or N2O. You will obtain the best performance under stock conditions with the recommended gap.

post #3 of 9 (permalink) Old 09-20-2001
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Re: Spark Plug Gap

I would go with .035 to .040 with a stock ignition and maybe .040 to .045 with a good aftermarket ignition system. Also this depends on if your running a turbo/nitros/supercharger. Increased cylinder pressure can really tax the ignition system if its not up to par in the higher RPM band. Frank..
post #4 of 9 (permalink) Old 09-20-2001
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Re: Spark Plug Gap

Well, thanks for the advice guys. When I pulled the old plugs out, they were gapped at .070. So, in the hurry I was in, simply gapped the new plugs at .070 and put them all back in. Then got on here and read your responses. Is it worth it to pull them all back out and re-gap them? Or am I okay leaving them where they're at? What are the pros and cons of gap sizes? Thanks.
post #5 of 9 (permalink) Old 09-21-2001
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Re: Spark Plug Gap

Yes, pull them all out and re-gap to our suggestions. Pros and cons--too large a gap will weaken the spark too little will not ignite the incoming fuel charge properly.. Frank..
post #6 of 9 (permalink) Old 09-21-2001
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Re: Spark Plug Gap

Alright, I pulled them all about again, and regapped them at .045. I noticed a better response from the engine, so I'm glad I did it. Thanks guys!
post #7 of 9 (permalink) Old 06-22-2002
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Spark Plug Gap Please Help

Hey guys I am getting ready for a tune in my 92 coupe, I am replacing spark plugs....But still have the stock ignition installed. I am planning on moving to a Crane HI 6s by the end of the month. I saw above that .35 to .40 for a stock and .40 to .45 for a aftermarket is the right gap. Is it ok for me to go ahead an move my gap to .45 or will this damage anything ???


92 LX Coupe --------
- 3.55's
- Incon 800TT (Install In Progress) , Kirban Regulator, Walbro 255, 36lb Injectors
- 180 Stat, Griffin 31" Nascar Radiator, Mark VIII Elec Fan
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post #8 of 9 (permalink) Old 06-23-2002
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not to be impartial...but good choice with the HI-6S... I think you'll like it. I'm still waiting on my money from BMW for saying how nice their car is
You can open your spark a little, with the box. a good rule of thumb would be not to open it to .045 from .040, but to open it about .004-.005. (i.e. if your running .038, go to .043, .039 to .044, etc.
of course others may disagree.
A tip you can do, if you're running single electrode plugs (not bosch +4's or splitfires, cut the electrode back to where its tip is halfway over the bottom. the take a file and round it off. Autolite has a plug like this already i believe, but this will help for a more powerful spark.
Are you going to go with the DynaMod or not right yet?
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post #9 of 9 (permalink) Old 06-24-2002
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Ignition or not you can run a .045 gap and be just fine. You wont hurt anything on your car. Later.

93lx - 8.2 @ 86 MPH 1.95 60'

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