340 popping through carb at low RPM.

Matrick69 said

It definitely not a pop pop pop. More like one or two pops on acceleration and then clears up once it's off that 1000-1200 rpm range. It will also do it randomly on the highway if the motor slows down going up a hill in 4th gear. If I speed up to keep the rpm up, it's fine

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See? That was a very important question that you ignored. Had I not insisted on you answering it, you would not have known that the camshaft and valve train has an over 90% chance now of NOT being your problem. See how easy that was?

I'll be damned if it almost doesn't sound like a couple of plug wires crossed up. 18436572 is the firing order, and that's rotating clockwise. Double check your firing order and let us know. And before you say it, don't say "I know it's right", go check it. I cannot tell you how many times I JUST KNEW I had it right and it wasn't. LOL