If your exhaust manifold valve is stuck open you will be fine. I would leave mine open on my 292 and it would be 30-35 degrees out and the motor would run fine. I had a similar issue...when mine was cold or hot everytime you stepped on the pedal it would hesitate majorly. That was caused mostly by a bad accelerator pump and a wobbly throttle shaft. So it ended up having a vacuum leak from the carb itself. Rochester 1 barrel carbs are prone for that. I would bye a new carb or switch to a slightly bigger one...like a holley 2 barrel and try that. Or fiddle with your air mixture screw and Idle adjustment again...I think it is just a worn carb. My 2 cents. T.J.
