Hotter makes it cooler

[Chevy nutcase]

When I got my 66 c10 it was bone stock and the temp gage didn't work. When I cleaned and painted the motor I replaced the faulty sensor with a new one and I replaced the old crusty thermostat with what they had on hand, a 160°. I thought it might help it run cooler but now that the gage was working it always seemed to run hot. It never overheated but it would hit the H and with a laser thermometer on the water neck I knew it was running around 190° - 195°. I was told it's not so bad if it stays there but I still didn't like it. When I got it inspected I told the old guy who owned the shop what I did and he said put a 180° in it because the coolant is moving through the rad to fast. I heard that theory before but hearing it from him affirmed my actions. I got a 180° and voila it stays much cooler.