Here’s the lesson. When you change a part. Take the time to make sure the replacement is the same...... This is a short lived plug from my Chevy Citation 2.8 V6 X-11 tow car. I changed the front bank but couldn’t get to the rears. Next morning got on the road at 3:50 am going to a race and within a minute on the interstate the engine cut out badly. I found if I ran in 3rd it would keep running. 3 hours later, all front cylinders were dead. I pulled the plugs and saw this.

The problem was that it was the right delco number but it had a E following. The E stands for extended, this plug has an extended tip and the front 4 threads were extending into the cylinder and I am sure were glowing red for the whole trip causing pre ignition. Amazingly I won the race and towed it home and changed the head gasket so I could race again the following week. 

All of this would have been had I just compared the new plug with the old.... Just a reminder to always check the parts to see if they are really the same.