my 89 rs with the 305 tbi, no ac. it has a new water pump..thermostat..coolant..no cracked block or head gasket damage. runs great but drive it 20 miles and it over heats, the coolant boils back up into the recovery tank. WTF!!!! IF I CANT GET MY CAMARO FIXED I'D RATHER WALK! HELP PLEASE!!!

 

Check your air dam... it is an integral part of the cooling system for when you are driving on the highway...which I am suspecting from your post, when you experience overheating.

 

are your fans coming on? maybe the relay is shot or maybe the fan sensor wire got fried.

 

fans are coming on and air dam is in place..yet it still over heats..even has the local chev dealer stumped...[timing is set right also]