If you idle it down too low, you will not have sufficient oil pressure. Without having a oil pressure gauge to know, you need to get it up to 550 to 600.

You capped off the vacuum source on the intake manifold for the PCV system and now the engine smokes. Connect the dots.

That rubber hose on the front, side of the valve cover looks short, but it should have connected into the carb air cleaner. Is that not correct?

At idle the PCV system should have a slight vacuum on that hose, drawing fresh, filtered air from the carb air cleaner. Air enters the engine through that hose, collects the crankcase fumes that you saw, goes through the PCV valve into the intake manifold and the engine burns the fumes.

If the PCV hose is bad, replace the hose.

You say it idles best when the mixture screw is 1/4 turn out. What exactly happens when you turn the screw out an additional 1/4 turn?? What exactly happens when you add another 1/4 or 1/2 turn to that and it is at one full turn out????


'67 GMC 3/4 292 4spd