1980 firebird formula coolant leak, frost plug?

it has a 305 carburated and on the driverside right by the manifuld and the oil filter on the underside there is a plasic part and it's leaking from there anyone know what the plasic part is?

Thanks very much, Cory

Sometimes, ordinary metal frost plugs are replaced with rubber/plastic expansion-type plugs. They are used as a temporary or quick repair for a demaged or leaking frost plug. They don't last forever, though.

Alternately, there are small block drain plugs right beside the oil pan, one on each side of the engine. Usually they are plugged with steel crew-in plugs.

Thank you very much