a thermostat is designed to open at a certain temperature,holding the water in the radiator till the thermostat reaches that temperature..thus allowing the water to be cooled in the radiator.he may need a larger radiator but switching to a cooler thermostat will definately make the engine run hotter,I run a 195 in my duster 340 and 200 is the hottest I have ever seen it in the middle of the day idleing in traffic in the middle of orlando and it was like 90's that day and I don't run a shroud,it runs a constant 190 degrees unless parked in traffic,I run the autolite plugs in everything.
