440 six pack high idle

The outboard carbs have an idle circuit. If you block them off from the intake the car will not idle well at all. You will be causing more problems.

don’t disconnect the outboard Mechanical linkage and drive the car. That linkage closes the carbs.

Male sure the outboards are closed and disconnect the vacuum lines so they will not open. then run and drive the car and see what happens.

Make sure the throttle cable isn’t holding the center carb open. Disconnect it and leave the return spring on and run the car and check the idle speed.

How much idle vacuum does this have? How big does the cam sound?