I recently swapped my 91 Camaro from TBI to a carburetor, and I have two black HVAC lines that run in the engine bay from the HVAC controller. I am trying to figure out if they both get hooked to the carburetor and if so where? I currently have them both connected with a T to a full vacuum line off the carb and my vents now function, but when I put the heater on I hear a whistling noise coming from the HVAC controller in the car. When I turn it to cool the sound goes away, but when on warm it is back. I am curious if my HVAC controller is leaking, or if I don't have those two lines hooked up correctly. My car only blows out of the top of the dash if those lines are not hooked up and I want my vents to work, which they do the way i have it hooked up currently. Any help is greatly appreciated.

Thanks.

 

One should go to the carb to supply the vacuum to power the HVAC doors.

The other should go to the heater hose valve on the intake manifold. It cuts off the flow of coolant to the heater core when the AC is in the "max" position.

 

As per five7kid's comment ,you are applying vac to a outgoing line from the controller when that line should be getting the vac from the controller.

Typically the vac line from the engine runs to a one way valve by the dist The rear port of valve goes inside to the HVAC and the side port has a rubber line to the vac ball up front that stores vac so your vent positions don't change when the engine vac drops.