I have a 67 chevelle with a 350, started it for the first time in months. I am pretty sure my timing is right, dut i get a rythmic backfire/popping from the tail pipes. and also a backfire through the carb when I give it throttle. It does this no matter how far i advance or retard the timing. It does not want to idle but I believe that may be due to carb issues, holley650. Anyone have any suggestions? Also, it is running extremely hot! can a slipped timing chain cause this?