Gapping spark plugs....will a smaller gap mean better gas mileage? - Chevelle Tech
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post #1 of 6 (permalink) Old Aug 20th, 07, 6:13 PM Thread Starter
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Kev
 
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Gapping spark plugs....will a smaller gap mean better gas mileage?

I just did my yearly change over of my ac delco spark plugs. I am running a 350 with steel vortec heads and R44LTS6 spark plugs. I guess last year when I put in my first set I didnt set the gap right and I think they were set at factory specs or around .060 or .065 give or take. I have done some checking and came up with .045 which my mechanic also confirms is correct for those heads. Would the huge diff in gap specs mean that I am now going to get better gas mileage or what? I know that running a wider gap means a bigger spark kernel and that running a smaller spark kernel is what I have now. Does smaller gap kernel mean hotter/tighter spark or what? I would like some other opinions from anyone who is knowledgable on this subject.
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post #2 of 6 (permalink) Old Aug 20th, 07, 6:30 PM
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Re: Gapping spark plugs....will a smaller gap mean better gas mileage?

I have always heard that the larger gap burns the fuel more efficiently. That is one of the reason's for hotter coils and ignition boxes. At the same time, You need to gap your plugs for your ignition. If it is too wide, you won't get an effective spark and it won't burn all the fuel. If your running a stock ignition then the factory recomendations should give you the best milage and performance.

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post #3 of 6 (permalink) Old Aug 20th, 07, 9:05 PM Thread Starter
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Re: Gapping spark plugs....will a smaller gap mean better gas mileage?

I am running a complete MSD ignition system. My old plugs were as stated but now the new ones are gapped at .045. It seems to be running a little rougher now with the narrower gap. Not too bad but noticeable.
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post #4 of 6 (permalink) Old Aug 20th, 07, 10:55 PM
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Re: Gapping spark plugs....will a smaller gap mean better gas mileage?

The main criteria for plug gap is the type of ignitition, fuel mixture, and intended use. Stock points ignitions may not fire gaps over .035 reliably (and max gap decreases with rpm). Electronic ignitions are capable of firing much wider gaps but most performance engines won't see any benefit (power or mileage) from gaps beyond about .045. I've seen factory HEI applications that called for .070 gaps but they were because of extremely lean mixtures in smog engines. The larger the gap, the more spark energy it takes to cross it. That extra energy results in a bigger spark which is helpful when mixtures are very lean (and also if they're really rich) but if the extra energy isn't available, there's no spark and it's a miss instead.
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post #5 of 6 (permalink) Old Aug 21st, 07, 9:11 AM
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Re: Gapping spark plugs....will a smaller gap mean better gas mileage?

Quote:
Originally Posted by 53Chev View Post
I just did my yearly change over of my ac delco spark plugs. I am running a 350 with steel vortec heads and R44LTS6 spark plugs.
Doesn't the final "6" in the part number mean the intended gap is .060? Therefore the side electrode is longer than the one on an R44LTS?
Sounds to me like you have the wrong plugs if you want a .045 gap.

If there's no misfire at the larger gap, a smaller gap isn't going to improve fuel economy.
If there's no misfire at the smaller gap, a larger gap isn't going to improve fuel economy, either.

How many miles are you driving each year? I'd be really surprised if you actually needed new plugs each year.
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post #6 of 6 (permalink) Old Aug 21st, 07, 6:13 PM Thread Starter
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Re: Gapping spark plugs....will a smaller gap mean better gas mileage?

Ok I finally got it and I am surprised it took me this long to figure it out. I went and picked up the R44LTS plugs and after putting them in, I noticed an instant improvement in performance and gas mileage. I am now using about 25 percent less gas then before. Thanks to those of you that took the time to offer advice
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