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10-29-2019, 12:27 PM
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#1 |
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Junior Member
Join Date: Jul 2002
Location: Scottsdale, AZ
Posts: 1,695
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Plug Gap 1975 350
Looked at this ol 75 Silverado last night. I just noticed the emissions sticker says 'Plug Gap - .060'. I thought HEI's were .045? Have I been doing it wrong?
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"I was patina when patina wasn't cool." 1973 Cheyenne SWB Gold White Fleetsides/Saddle |
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10-29-2019, 12:41 PM
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#2 |
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Senior Member
 
Join Date: Jan 2001
Location: Orem, Utah
Posts: 7,794
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Re: Plug Gap 1975 350
No, when the HEI first came out GM recommended a gap of .060. They later changed it to .045 because they had problems at the larger gap as the plug electrodes wore. The .045 is what I run in mine.
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I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man. - Thomas Jefferson |
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10-29-2019, 02:30 PM
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#3 |
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Registered User
Join Date: Aug 2012
Location: Oklahoma City, OK
Posts: 2,476
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Re: Plug Gap 1975 350
My 75 had the same .06 gap specified. Needed a special plug with a tx suffix for extra wide gap or something. Have since switched to the normal plug and .045 gap. Didn't notice any difference in starting or running performance.
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11-07-2019, 03:05 AM
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#4 |
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Registered User
Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 2,629
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Re: Plug Gap 1975 350
A little fundamentals may be in order. HEI's came out with an increase in voltage and or amps to get mixtures burning better. The thought was you could create a bigger spark I suppose.
Tried my stock 70 chevy Gen 1 block with and HEI and R45ts plugs at different gaps. Did everything from .035 to .060, still to this day it seems to like .045 more than anything. Now if you really get into it, I supposed A/F ratios would matter as well as timing. I bet that thing was lean from the factory. Dawn of the EPA era. |
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