I have a 68 250 in my 50 Chevy sedan.It has the stock Rochester 1bbl. At Idle it kind of stumbles. So I pulled the PCV and put my finger tightly over it and the engine smooths out real nice. Also when I screw in my air/fuel mix screw in. I don't notice any change until it is almost all the way in. I'm kind of lost on this. I sprayed some wd-40 around the intake ports and carb while it was running and their was no change. The PCV is new but could still be bad. Any thoughts? Thanks, Todd