Back firing and rough idle after hard driving
 

Has anyone experienced this problem after A/Xing? 78'sc motor. Temp ran up to approx 220deg. It seems that now when the car is started in the morning I have a very rough idle and constant backfire until warmup. At that point back firing seems to stop or at least only happen at times. I realize that may be due to my richening the fuel mixture due to fact that the car began ideling at around 500rpm. I pulled the plug wires one at a time and 2 cylinders didn't seem to make the idle drop. Could it be the plug wires?

Just fo the heck of it, check to make sure your pop-off valve is snugly in place. This presumes you have a pop-off.

pop off valve is installed. I will check that tonight. By the way, is there supposed to be a plug on the vacum opening on the bottom driver side of the cis airbox? smog equipment has already removed. Thanks