Originally Posted by sbchevfreak
Make sure the chin spoiler and all air dams are in place. This era Camaro has a very small grille opening, and uses these pieces to direct airflow from under the bumper through the radiator core. If they are missing, it will overheat. You also need to have the t-stat in, for the reasons Cobalt mentioned.
I´d go with this as well, that airdam is critical for highway cooling.