Re: 1954 359 L8 / Iridium spark plug in place of Autolite copper resistor 308 spark plug

Posted by 54packpac On 2022/3/28 15:19:42

Riddle me this. I'm almost over it and not to beat a dead horse with a stick. On JEGS NGK has an iridium 14mm x 3/8" reach plug. Albeit the gap is 0.059. The copper Autolite gap is 0.025. I'm wonder if there is a conversion chart for gap in copper vs iridium plugs? Gapping iridium plugs is very fragile I heard. Of course the next issue is heat range. NGK might go as high as 8 vs the Autolite 308 of 12. NGK shows a GM 1973 455ci engine as compatible. This all goes out the window if I have to adjust the timing and fuel enrichment correct?

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