In Reply to: Which up-dated spark plugs for my 8n? posted by Jeff in Maine on October 03, 2020 at 19:48:45:
This was copied from another source: Does a good job of explaining the difference.
We recommend the HOTTER AutoLite 437s' gapped 0.025" for todays un-leaded fuel that FOUL the cooler H-10 or 216's. As you discovered, the 437's ceramic nose is LONGER, why? 'cuz the LONGER the thermal path to the cooler cylinder head the HOTTER the sparkie which then BURNS the oil and lead deposits from between the gap.