A common misconception (regarding a thermostat as used in the cooling system of a liquid cooled engine) is that it is there to maintain the coolant at the temp that the t-stat is rated for.
That number - the one stamped into the shell of the wax capsule (180 F in your case) only reflects the temperature that the stat is designed to open at. After the coolant reaches the rated temp, many other factors become involved. The valve - after opening - slowly modulates and controls the flow of coolant to the radiator. Engine load, rate of coolant flow, efficiency of the water pump and radiator cooling capacity are the primary factors affecting your coolant temperature.
Read this - it's written by a company that sells low temp t-stats and they have an agenda - but it's still pretty good:
The Function of the Thermostat & Cooling System Basics
The biggest misunderstanding about thermostats is that people believe they make the engine run cooler. They don’t necessarily do that. The cooling system and load on the engine determines how hot the engine gets, the thermostat fully open will still be the mercy of the coolant system’s ability to remove heat.
Most engines run slightly above the thermostat’s minimum opening temperature under normal loads. Under high loads, they will run at or above the thermostat’s fully open temperature – in other words, under hard driving, the thermostat’s opening temperature is completely irrelevant.
The thermostat can only determine when the cooling system is allowed to start cooling the engine. It sets a floor, not a ceiling on engine temperatures.
The thermostat basically behaves like the hot and cold knobs in your shower, if the water is too hot, it turns the cold on a little more and if the water is to cold, it turns up the hot water.By regulating the flow through the cooling system it speeds up and slows down the flow of coolant into and out of the engine block.
In liquid cooling systems, the ability to cool is determined by a number of factors, but the basic keys are the surface area of the radiator (how big/how many small fins), the air flow through the radiator (fans on/off, speed of car), and how quickly or slowly the cooling fluid goes through the radiator. If the coolant spends a small amount of time in the radiator, it loses less heat. If it spends a lot of time there, it loses far more heat. Therefore you don’t want the flow to be too high as the cooling system’s ability to cool the engine will be reduced, not increased.
The thermostat is there primarily to help the engine warm up in the morning. As we discussed in a previous article, the engine is designed to operate at it’s operating temperature. Most engine wear occurs when the engine is cold, once it’s warmed up there is very little wear in a healthy engine. Thus, we definitely want to run a thermostat to allow the engine to warm up as quickly as possible until it reaches our desired and designed operating temperature.
If the engine is below operating temperature, the bearings, rings, and other components are not yet expanded in size and therefore they “bang” against the other metals in the engine more than they would at operating temperature. No good.
So if we don’t run a thermostat at all, it takes a lot of constant load to get the engine properly warmed up and to keep it up to temperature on cold days.
We also in some circumstances may experience overheating if flow through the system is too high as the coolant has to spend a certain amount of time in the radiator to actually cool down.
(NOTE: the above statement is wrong on several levels. It is contrary to the basic thermodynamic principles involved in a heat exchanger - but I'm not getting into it)
Some race teams do choose not to run a thermostat, but they are the minority. They usually run at least a restriction plate in place of the thermostat to slow down flow and allow some warm up to occur. The reason that they may not run one at all is usually to remove a point of failure in endurance type races. In other words, if the thermostat fails and sticks closed, it could cause a pit stop or end the race. By removing it, they tolerate possible engine wear since they know they’ll be at high loads throughout the race. Their cooling system is usually tuned to compensate for the lack of a thermostat as well.
Running the factory thermostat will on the other hand ensure that the engine comes up to the designed minimum temperature very quickly. Until the engine is up to temperature, there is no cooling occurring. The factory thermostat will not however change how the engine runs under load because the thermostat will be fully open when under load. It effectively isn't there under load.
