Cooling Issue! HELP PLEASE!
 

Can anyone help with the cooling issues I am having?! I have replaced just about everything I can think of minus the heater core. But I got a new water pump, Thermostat, hoses , and went to the 79-82 radiator, because I read on here that the short 3 row, had better cooling capacity. I have an efan that moves 2800cfm, but as Im driving, thatg shouldnt make a difference. It only does it when Im driving, if I stop, it runs normal.
Running out of time, Help Please.
This for the 85 GS
Mods are mild streetport
Full racing beat exhaust,
Racing beat holley with intake
and no rats. All I can think of that can affect the cooling.

Have you done a flush of the cooling system (motor specifically)? Is it an older motor? If it is then you could have a coolant leak in the motor that is boiling the coolant.

You do have the correct thermostat for rotary, you know standard looking thermo will not work. Have you run it without the radiator cap on to check for bubbles? Take it up to 3k rpm.

Belt slipping? Radiator clogged? Are you losing any coolant? Is your timing correct?

That's about all I can think of right now...

Did you put on a new radiator cap? Also, once the system was back together did you run the car with the heater on so that all the air in the system would escape.