Recently picked up a mid-80s Bianchi roadie. It's a dull red color. Bottom bracket serial reads S4167C5.

Maybe a Stelvio? It looks a lot like this Stelvio-- Road Test/Bike Review (1985) Entry-Level Racing Bikes

It has a "Bianchi Special Columbus" badge on the fork, and a similar "Bianchi Special Produzione Columbus" badge on the frame.

Without wheels or a chain, the otherwise-complete bike weighs 14.8 lbs on my luggage scale.

It's no museum piece, with plenty of little chips and surface rust spots. (The irony of wanting to identify it is I'm not going to make any effort to keep it original.)

The rust (original?) calipers are Modolo. The (original?) pedals say Lyotard 82, though I see this was stock on an '85 Stelvio so the 82 is not the production year.

Will post pics in a follow up.