Originally Posted by dgordner
What would I be looking for around the porcelin on the plug?
Cracked porcelin on the exterior of the plug will make it arc or ground (dead-miss) to chassis under a high load, I.E. WOT, that's when the ignition is at its weakest and we all know electricity always finds the path of least resistance and it's much easier for it to ground to chassis than ground through the plug.
A cracked insulator can cause a miss fire, it will not arc at the tip or on ground electrode but rather on the inside body of the plug making it have a miss fire.
You might just be a tad on the lean side if at WOT you aquire a mis-fire, you could have some trash inside the main jets, I've actually had this problem before on a 1966 mustang 289 2 barrel I had, it ran like a devil till you got in it ( WOT) then it would miss like crazy, that one little piece of thrash in one jet cost me a couple hundred dollars worth of ignition parts till I figured out it was the carb.
Cp