Would my dual snorkel scoop be affecting my cooling at highway speed?

89on35s said
74 Duster
360/A-500/3.23 gear
Stock Ignition
670 Holley Vac secondary carb
Cheap headers and dual 2.5" exhaust
Factory AC with 26" rad (recored to 3 core), factory shroud, 5 blade clutch fan from a mid 80s Dodge truck (1" off the rad)
External trans cooler
Timing set by vacuum gauge cause the balancer mark is way off. Vacuum advance currently disconnected.

Last Friday at the strip, it was started, stopped and idled between my 10 passes with no AC on for a few hours and the temp never topped 160*F. In traffic with the AC on, it does not go past 180*F. On the highway with the AC running 70ish MPH at 2000 rpm the temp goes just past 200*F and drops back to 180 once you are back in traffic.

Is this caused by my timing being out of whack or could my dual snorkel scoop be creating a positive pressure under the hood that limits airflow across the rad?

How does timing affect operating temperature? I searched and could not find the answer to that.
Cley

If the scoop is hooked up like it's supposed to be (into the carb) then you shouldn't get much back pressure at all. If it's open under the hood then maybe yes. The more advanced you set the timing the hotter it will run. Also, for the highway, any places around the radiator where air can bypass the radiator fins will/can cause a problem. The trick is to seal all spaces around (top, bottom, sides) the front of the radiator so the air has no choice but to go through the radiator fins. Most Moaprs came with a rubber cowl to hood seal on top of the radiator just for that reason. Also, your condenser should be mounted as close as possible to the radiator to prevent cavitation.
Treblig