vacum problen on carb

[ole yeller 1978]

I have a 300 inline with a one barrel carter carb. On the carb by where the electric choke bolts on is a fitting that is threaded on the inside. Nothing is hooked to it, and it sucks air like crazy. I looked in my chiltons, it shows the carb and the fitting I am refering to but dosn't say anything about what hooks to it. I know I have to do somthing with it but don't know what other than block it off. Oh yea it is on a 78 f100. Thanks for any help.
Jeff

[dvldrmmr]

sounds like thats where the hot air tube from the exhaust connects - i dont have mine connected but mine doesnt suck air so i cant say for sure ... this is on a 81 carb though, so it could be something different for you ... someone more knowledgable than me chime in ...

travis

[javi2001]

Yes this is the Hot air tube. It is supossed to be connected to stock exhaust manifold. Was the manifold changed for a header? or an EFI one?

You can simple plug it BUT the climatic control is not going to work any more. If the manifold was replaced, you can make your own hot air tube using 1/4" cooper pipe a flare nut an a piece of hose.