I recently decided to increase the gap on my denso iridium plugs after seeing that some other users had done this with good results (RT, cdelena).

Gap when I originally put them in was .040"; increased the gap to .045" (not as much as RT's .050", but same as cdelena) and the car ran like crap! Felt like it was missing under hard acceleration. Put the gap back to .040" and the car ran fine.

OK, here's the point of this post:
When I re-gapped to .040, I noticed that the anode (top part) was not completely over the electrode; in other words, the spark from the center of the electrode would actually have to travel at an angle to get to the edge of the anode instead of straight up. I didn't think much of it at the time and didn't do anything about that, just adjusted the gap back .040.

The more I thought about it, however, the more it seemed that this may not be optimal. Because the spark would have to travel at an angle from the electrode to the closest point of the anode, the effective gap might actually be larger than what I was measuring. It is possible that when I gapped the plugs to .045, I moved the anode both UP and BACK; when I re-gapped to .040, I only moved the anode DOWN, leaving the end point further back from the electrode tip.

Today, I took the plugs back out, adjusted the anode to make sure it was completely over the electrode and gapped them to .042. The car runs GREAT! Feels better than the previous .040 gap.

Maybe I'm just a spaz mechanically, but I relate this for others that may have had less than satisfactory results with denso iridium plugs and may have done the same thing I did when changing the gap.

 

I noticed the same thing when I pulled my plugs to check for tightness and detonation.....I tried to bend it back down so that it fit properly over the center