Well, Whats with these 1776 engines ? This is about the 5th one in the last year that I`ve heard about with some kind of "pooping and poping" problem.  Timing to high, carbs not in sync, fouled plugs, plug connectors bad, resistor in the rotor bad, cap bad , Advance in the dist. not working .  Without seeing or hearing the Varmit , Its hard to say whats wrong ,but all of above could cause the problem plus a few other little things