Thread: correct 478 spark plug
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Old February 21st, 2024, 04:11 PM
Prowbar Prowbar is offline
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Truck: 1965 GMC 1500, 478 V6, SM420
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Default Re: correct 478 spark plug
From my 1965 manual, the factory spec is a C42N plug, so a little colder. 3/4 reach is fine.
Haven't had any trouble with my 478 dieseling. Mine is a 62.
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