Hmmm another thing I just thunk of.. when the positive electrode is drilled, if it's a copper plug, one might get down to the copper, or a lot closer to it... now this may effectively reduce the resistance at high voltage, because I'm thinking that the core nose is part of the resistance of the plug, and if one allows the high voltage to take a route where it can move as surface charge, it miiiight be a less resistive path than if it had to go all the way through the bulk of the carbon stuff.

I'm gonna have to measure resistance to the tip and resistance to the bottom of the cavity next time I drill one to see if they are the same or not.

Edit: Gah, and now it makes sense why some people expect it to blast ions out of the cavity. I was always skeptical of that, but if the energy is passing up the sides of it as surface charge it could well make ions in whatever gas is present, which then become the path of least resistance, so the spark jumps through them, heating the gas more and expanding it, so it jets out with the spark and is pulled toward the negative.... And... that will only happen if the core nose is resistive... hmmm seems to be a case for picking your mod plugs carefully, I'm pretty sure autolite were constructed in that way, will have to check up on anything else...

Yes!! I've thought of that tool as well.......but don't have one on hand.

Thanks for the link.

From what I could tell on LaPointe's site a larger hole wasn't any more efficient than a smaller hole. The smaller hole lasts longer. I think your hole is too large and the plug will wear out too quick. The hole interferes with the cooling so the tip will run much hotter than it is supposed to.

Harbor Freight 94606 has the right size drills.

An automatic center punch will smash the electrode in. A drywall screw will dent the metal just enough to get the drill to start though I have a drill press.

I've tried but Halo plugs for my cars are never available.

What about just chopping the ground strap back so it only covers half the center electrode? That's an old performance mod that gets rid a lot of the quench area that this precision drilling is supposed to do.

There was another recent thread on sidegapping... on Marvin, idle quality wasn't so good, bit better pull above 2000 though, mpg wise less than 5% difference, or I'd have noticed.

I have completed my indexing and drilling mod to my existing Denso Iridiums. I will report back when I have several tanks of gas burned up. I have been averaging 16.5mpg in 70% city driving.

For those of you with Tundras or any other truck, what mods have you done in order to increase FE?