Originally Posted by oilcanhenry

There _SHOULD_ be a "can" (looks more like an expanded disk) on he side your ignition distributor. This is the vacuum advance device, that adusts your ignition timing, along with a centrifugal device that runs inside the ignition distributor and is not dependant on any vacuum to operate.

This old-style device needs to be connected to your carburetor by a small hose, for your motor to operate correctly.

Your Chevette motor was designed to work with BOTH ignition advance devices, when it was installed as OE, in the old Chevette that it was pulled from. Barring that, plug any and all open vacuum hoses, as "oldchevy" suggested here.