SBC350 - 160F while driving, 200 at traffic light

[russgt]

It looks like you installed a flex fan, are you still using it? I would suspect that the extra air flow from the flex fan at speed is causing the extra (160 degree) cool down while driving. A clutch fan would disengauge at speed but the flex fan is still pulling. At low engine RPM (while sitting in traffic) you do not have enough coolant flow/air flow to keep the engine from warming up (200-210 degrees) the good new though is that your electric fans are working correctly and can cool down the engine.