Find someone with a Champion book and use what it calls for in the marine section. Or call me, I have the book and do lots of Olds motors. Next: unleaded fuel will not leave much, if any color on the plugs, at any reasonable jetting. Plugs are properly read with new ones, of the correct heat range, in an engine thats not an oil burner, by looking at the very deepest part of the center insulator. That should be a white/parchment color. The side electrode should have a heat discoloration band of a straw color or yellow that is centered on the knee, or bend. If too rich= discoloration more towards the tip of the side electrode. Too lean, and the discoloration will be more toward the threads. This assumes the correct heatrange plug. You will make more power with an extended nose plug, and with less total timing. Champion plugs have a bright plating that allows easier reading of the plugs. Any other than a standard single electrode plug is Bull---t. Don't waste the time or money. Fine wire electrode plugs (AKA platinum or Rhodium) will make less power. IN A NON COMPUTERIZED, CARBURATED ENGINE! Any extra side electrodes will slow down the flame front, and will make less power, unless you are running too much timing. The shrouding effect slows the burn. A split electrode promotes detonation due to the smaller mass of the tip. We have seen LOTS of them with the split melted off. A proper, single standard electrode plug at the correct timing will make the most power. All of this and more was covered in the old Hotoat article from a few years ago. TIMINATOR 623-877-8553
