1970 GMC Truck carb.

Carburetors don't pop. Worn, fouled, or broken parts can cause a backfire "through" the carb, but it's not the carb. Ignition timing, point dwell, if you have the old style distributor, a partially fouled spark plug, a weak or loose plug wire, and maybe even a camshaft with one or more worn lobes. You have lots of things to check, but you will find the problem if you are patient and take your time. Good luck.....mickey-d