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

Posted by 54packpac On 2022/3/28 10:52:20

My 1954 359 L8 currently utilizes Autolite copper resistor 308 spark plugs. The gap is 0.025. Thread size is 14mm. Reach is 3/8". Heat range is 12 (cold). Seat type is gasket and tip is short projection. All works very well. Does anyone know if there is an iridium or platinum cross reference? What are the pros and cons of a modern hotter plug in a 1954 359 aluminum head should there be a cross reference? Holley MSD has a 14mm, 0.4375 reach, heat range 6 (hot) iridium plug. Will a longer reach be detrimental? Will things go boom and melt? Thoughts are welcome.

Attach file:

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  54packard359autolite308plug.JPG (114.72 KB)


  032822msdirridiumplug.JPG (62.41 KB)