Yep those are the ones. I was told by my uncle that they are caused by a too lean mixture. So we have been backing off the mixture screw to get a richer mixture. It has helped BUT we think that we better time the engine with a vacuum gauge instead of a light. The truck has a Langdon HEI dizzy and he suggest 10 degrees advance. We are going to reset idle to 500 then mixture screw 2.5 turns out then turn dizzy to get max vacuum. While its running we will spray starting fluid around the manifold to see if there are any leaks. I hate the burp noise!!!! But have no idea if it hurts the engine no one has chimed in on that....if we are wrong with our plan please (anyone) chime in. As an ex-Army guy I take orders well!