Originally Posted by beertracker
I need some ideas on this problem. According to the tach the engine is idling at 2000 rpm. The tach is good as the engine is roaring at idle. The throttle plate is fully closed and there is a gap between the idle speed screw and throttle stop. Moving the fast idle cam does not help. The idle mixture and fast idle mixture screws are set at 4 turns out. It's a 700 cfm 4 barrel Q-jet. I haven't done any internal work on the carb.
What should I try next?
If I understood you post right, the throttle blades will not close any more than they are now- that is, the throttle blades are fully touching the throttle bores of the carb, but it's still idling high?
Look it over very closely for a vacuum leak would be the next step.
It could be losing vacuum at the carb base, the vacuum hoses coming from the carb or intake. The carb top or base can be loose from the carb body- this will cause vacuum leakage internally in the carb.
If the brake booster is shot, it can be leaking vacuum.
Is the car shifting OK (if AT)? Is the vacuum advance working?
Has the engine or the carb been sitting for a long time? Did it just start this, or?