[madtexan]

Hi All,
This one has me puzzled. My GTO does the opposite of what most other cars do.. It cools when idling in N but creeps up when driving say 30-50 MPH even on 78 deg day.

car details:
Orig 400 YS block w RAIII cam w quadrajet carb. Auto trans 200R4

20" Mr Cool electric radiator set to come on at ~190 deg. Installed per Mr Cool instructions w provided shroud and then placed OEM shroud on top as you can see in pictures.

I think 180 deg thermostat.
30yo OEM style radiator. 3 core.
30yo OEM water pump.
I drove the car today and it heated up to abt 220 and then parked in driveway idling in neutral and dropped back to 180.

Any Ideas which part to change first?