best for spark transfer; dull or sharp edges?

12many said

I’ve done that to a set of Autolite race plugs like he mentions, even though the end is ground back and rounded there is still a 90° edge. Kind or a tedious job grinding and trying not to hit the center electrode as you grind but a neat mod nonetheless

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Yep that's what I'm running too
Autolite 3924R
It was tedious and took some time
I used the end flap off the spark plug box
To put in between the center and ground electrodes to keep from damaging it with the file.
They still look great after about 1500 miles
I was running the standard Autolite 3924's
Before switching to the Race plug.
I think they are a click cooler plug by design also.
So far So good!