[QUOTE=kstyer]Yes. The thermostat also acts like a restrictor when it's fully open. At some engine speeds and temperatures, it's okay to go without.
BUT, under some conditions, the unrestricted flow actually goes into and out of the radiator too fast. The result is the coolant never cools off. It gets through the radiator so fast it's still hot comming out of the radiator. As a result, you can overheat.
Also remember when a thermostat opens at 180, it's open. Any temp above that is a function of the heat created and the cooling system balancing out. if the engine ran at 200 for an example, it would still run at 200 if it had a 195, 180, or 160 thermostat.
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Man Ken, I've been in the cooling system business for 37 years and I couldn't have said it better. The myth that I hear often is the lower the t-stat temp., the cooler the engine will run. Not true under high RPMS.
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Click on images for Before and After pics!