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Author Topic: 1975 .060 plug gap(!?!)  (Read 6111 times)

Offline TandocTools

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1975 .060 plug gap(!?!)
« on: December 05, 2010, 05:22:26 PM »
My Chilton's lists the factory plug gap for my 75 GMC C15 with a 350/4 barrel and H.E.I. at .060--Can this be right?  I just got some iridium NGKs that were gapped for my application from the factory at .035.  Why so different from GM's specs?  I know how to gap iridium plugs so that's not a problem, but that's a bigger gap than I have ever seen on a stock vehicle and just wanted to double check before I install them!
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Offline ohio hab

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Re: 1975 .060 plug gap(!?!)
« Reply #1 on: December 05, 2010, 06:12:13 PM »
I use .045, never used .060, seems to big a gap for stock ignition. I would only use .060, with an Msd or like aftermarket ignition.
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Offline VileZambonie

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Re: 1975 .060 plug gap(!?!)
« Reply #2 on: December 05, 2010, 07:04:28 PM »
There were two specs depending on the plugs used. One was .035" the other was .060" do you know the engine code? Y or V? What plugs are you running?
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline onelow84

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Re: 1975 .060 plug gap(!?!)
« Reply #3 on: December 05, 2010, 07:25:26 PM »
quite a bit of newer cars/trucks are .060 I wouldnt think you would have a problem unless you have a lot of blowby or something. those NGK's are good plugs. I would go .045 but thats me...
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Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #4 on: December 05, 2010, 07:28:14 PM »
The plugs were NGK YR5IX but I'm not sure what code I have.  On the build sheet and on the glove box sticker the only code I see associated with my engine is "7F LS9 350CU V8 4BBL". Am I not looking in the right place?
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Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #5 on: December 05, 2010, 07:30:33 PM »
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Offline onelow84

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Re: 1975 .060 plug gap(!?!)
« Reply #6 on: December 05, 2010, 07:35:54 PM »
watch out for problems with that clear cap, I have seen people have trouble with them arcing
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Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #7 on: December 05, 2010, 07:39:54 PM »
Will do.  I'm just using it to "scrape by" until I can afford a D.U.I.!
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Offline VileZambonie

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Re: 1975 .060 plug gap(!?!)
« Reply #8 on: December 05, 2010, 07:45:27 PM »
.035" on that plug

I've had a clear cap on my 85 K20 since I put the engine in... Haven't changed it yet and that was Feb 2008
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #9 on: December 05, 2010, 07:51:30 PM »
So I should leave it at .035 or open it up to the GM spec of .060 or something in between?  What motor is my Chilton's referencing as .060 if not the 4bbl 350 with H.E.I.? 
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Offline VileZambonie

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Re: 1975 .060 plug gap(!?!)
« Reply #10 on: December 05, 2010, 07:52:02 PM »
.035"
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline fitz

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Re: 1975 .060 plug gap(!?!)
« Reply #11 on: December 05, 2010, 07:52:12 PM »
My Camaro has a DUI HEI ignition with a clear cap on it.
Reading this post made me realize that cap is about 10 years old now.
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Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #12 on: December 05, 2010, 08:53:00 PM »
Now I am compelled to try both!  I'll report my results!
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Offline Irish_Alley

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Re: 1975 .060 plug gap(!?!)
« Reply #13 on: December 06, 2010, 02:47:58 AM »
the engine code vile was talking about is the vin number engine code it’s the 8th one in from the left to right
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Offline TandocTools

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Re: 1975 .060 plug gap(!?!)
« Reply #14 on: December 06, 2010, 10:33:33 AM »
When I went to get my tags the clerk said my VIN was weird--the eight digit from the left in my VIN is an 0.
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