It has been scientificly proven that a bumblebees and wild turkey cannot fly. They do. Just as bublebees fly, engines are more likely to overheat without thermostats. The statement more flow cooler engine seems correct the way it was presented but it ignores some factors not presented. Consider this, the engine depends on the coolant,oil,octane of fuel,timing,type of metal,thickness of metal, shape of metal,air flow around said metal,the engine compartment itself and last but not least ambiant temperature. Designers through the years have engineered these engines to keep a delicate balance of all these factors and more. We benifit today from one hundred years of trial and error.
I'll use two engine types to make my point. The Model T was equipped with a 4cyl engine that had no water pump. It relied on convection to move the water through the engine. As the engine block heated hot water would rise into the radiator from the engine block this forced the cooler water down through the radaitor into the the block, a circle. In conjunction with oil airflow temp. ect ect. the engine functioned well for 1908. Look at 1908. Rural areas,rough roads with little traffic,and longer trips with fewer stops. By 1927 problems were beginning to show. Model Ts had a tendancy to run hot and boil over in the summer especially in cities and urban areas. Why? Look at 1927. Stoplights, heavy traffic in the city,pavement,Shorter distances but more time driving due to traffic. Why did the T overheat? It was not designed to function in stop and go traffic on Mainstreet in July. The balance was upset. The cooling system could not cope. The convection that worked so well in 1908 could not overcome the change in driving habits. The engine block heated the water normal convection began but due to the reduction of air flow the water became super heated because it stayed too long in the block. The hotter radaitor I'm sure was removing more BTUs "heat" but it was not enough. The longer it ran the hotter it got. What helped fix this problem the waterpump and then the thermostat.The water pump cooled the engine a great deal but it became cold natured in winter and still would over heat at times in the summer. To explain the thermostat I will use a later engine known for it's overheating problems the flathead V8. Truthfully the flathead was designed for running in the cold Dearborn winters at 10 below. At at 100 in the summer the flathead had to be driven carefully to keep from overheating even brand new factory fresh with all the bells and whistles. Hotrodders at first blamed the thermostat and removed it. It seemed to run cooler for a while but it seemed to get even hotter the longer the engine ran. Why? The balance was upset. The dual water pumps and massive raiators of the flathead were designed to keep that hot running engine cool. The pumps flowed massive amounts of water. It took longer to overheat but it still would overheat. The superheated water comming from the pumps so fast they went through the massive radiator with no time to cool properly. This was OK until the whole volume of water became overheated and could no longer remove the excess heat from the block. The radiator even though hotter and removing more BTUs was losing the battle to the superheated block. A circle. In this case without a thermostat the water was moving to fast and overheating. The exact opposite of what happened to the convection cooled Model T. Same same but different. The hot rodders solution was a flat washer in the thermostat housing with a one half inch hole. This gave enough restriction to let the radiator do its job. Most of the time this cured the problem. It's that delicate balance again. The thermostat slows the water down a little even when it is fully open. It is documented that racing engines of the flathead era did better and did not overheat as much with the washer than without.
