I have a mild 360 that I race that is approx 10:1, edelbrock heads and a run a mixture of 1 gal 110 + 3 gal 93 pump gas. 3 or 4 years ago I was putting new plug wires and changed the plugs and notice I had 2 or 3 (I can't remember) plugs that the ground electrode was broke at the bend part. I figured the plugs were old since I didn't remember changing them recently. I just tore the motor down for a freshen up this past month and I had 3 more that were broke. Cylinder 1, 6, 8. I know these plugs are less than 2 years old, so now I"m questioning if I'm running the right plug. The plugs are autolite 3924's. So I guess my question is first off what is causing this? and obviously what do I need to do to fix the issue to prevent this from happening again?