SBC350 - 160F while driving, 200 at traffic light

[78 Chevyrado]

How can you tell what the temp is when your going down the road? what are you using to measure temp. The dash gauge is worthless for telling actual temp numbers, and the cap in the radiator can be off by as much as 10-15 degrees difference between the radiator and engine block, especially if the T-stat is closing. The only way to know the engines real temp, is to measure directly from the block, cylinder head, or intake manifold BELOW the T-stat.

When my intake reads 198 in my truck, at the radiator it reads about 182.

If you're engine is truly cooling below 190-195 degrees, the T-stat is what it is, unless you have a bypass somewhere besides the heater hoses.

If you are going by the radiator cap for temps, double check it against a known good thermometer, just in case. If you can get your hands on one, try to come up with an infrared thermometer. They are awesome.

Are you using the air conditioner? depending on how you hooked it up, the AC may make the fans run when it does. My truck runs the coolest at a red light, with the AC on.