This is a 1975 460 with I believe a Motocraft 4350. It has been sitting for two years and am trying to get it going. The engine starts fine but idles around 1700 rpm's. Also, when I open it up and kick in all barrels the the secondaries stay opened and then it idles around 4300 rpm's. They won't close until I shut the engine off and restart it. I have checked for vacuum leaks with propane and found none. I have actually directed the propane directly down the primaries and nothing happens. I have checked to make sure that the primaries are pretty much closed at idle and they are. If have turned the screw in and out on the front of the carb with no response. I only have the tranny, brakes, and vacuum advance hooked up and everything else plugged off.

Any idea what this could be? Is there an idle adjustment screw somewhere I am not seeing. I have tried adjusting the actual linkage and nothing happens.

Any help would be great!
Shane

 

Sound like the plates are binding um inside the venturies.
I would thake the carb off and look at the plates on the bottom and see if there isn't some build-up in the venturi area causing them to stick.
Jimmy

 

up here , rust is a real problem even if they havent been sitting . we start the engine ,and while keeping it running ,spray wd40 down the throat of the carb at the same time actuating the linkage and spraying it. if its not real bad ,and yours doesnt sound like it , it usually works

 

I appeciate the idea. I've actually just ordered an Edelbrock 650 AVS off-road carb to replace the 4350, but while I wait I'll try your idea.

Shane