I set the gap to .025 You should always check the gap on new plugs. I have found some set way to big out of the box. I think the 386 plug is a resistor plug and will work, but as Richard said, the 3116 plugs do seem to work better. When I got my TO20 I installed the 386 plugs because they came with a tune up kit I bought online at the time and I ran them for a few years. I later switched to the 3116s and the engine seemed to respond much better.