Loud pop and sputter on WOT? 68 318 Barracuda

Traxfish said
Thanks! That was very helpful in visualizing what's happening. I will pull the plugs and see how they are after the trip. I drove 300 miles round trip for the eclipse.

Reading an AMC manual for later BBDs, it suggests adjustments to the metering rods are required for heavy load enrichment. Am I reading that correctly? I'd have to study further on how exactly to adjust the metering rods.

*added* The vacuum advance I've had a lot of work on. I ended up replacing the entire distributor because the advance diaphragm broke. It's not solved the hesitation issue.

BTW
Overheat can cause a plug insulator to crack or crack off, which has the potential to damage your engine.
But the thing I want to say is that at low load setting with a conventional coil, you might never know it! However, as the load is increased, the plug may not deliver it's spark to the tip anymore, but take a shortcut out the crack instead, and the fuel-charge in the chamber may not get lit, or comes late to the game. Depending on your throttle-opening, you may not even notice the 12.5% powerloss. But at WOT you will.