Trying to figure out whats going on with my motor. 70 Skylark 4bbl 350. Was a 2bbl but swapped to a quadrajet. Anyway it has a backfire in the passenger side exhaust. Its also rythmic so I'm pretty sure its one cylinder. Had some lifter tick a few weeks ago but I changed the oil and it went away. Just noticed the pop in the exhaust now, but it could have been there for a while. I pulled the plug wires and put a spare in. They are all firing. Messing with the timing can mellow it out some and happen randomly but not go away entirely. What could cause this and what should I check?
