[cadillac_al]

Eventually you should notice the coolant level going down or the trans fluid going down or the engine oil too. It's pretty rare for Chevy headgaskets to fail. Does that smoke have any smell to it that you could identify? If it still runs fine during the smoking then it must not be the carb. The earlier tip about the trans fluid should be verified. Remove the hose from the modulator (or at the manifold) and see if it is wet in there. If it isn't trans fluid then it must be burning oil. Valve seals are usually pretty consistent; worse at start up and not so bad when running. Does you valve cover have a baffle in the PCV hole?