180* vs. 160* Thermostat?

Tedderdog

Member
I am replacing the Water pump and my 1964 Buick Skylark, 300ci, no AC. Since I am doing that, just as well replace the thermostat. I have two choices. 180* & 160*. They both will fit but am wondering what the best choice would be. Much appreciated! Jerry
 
180 or 160

Contrary to popular belief, the thermostat does not regulate engine heat- doesn't matter if you run a 160 or 180. Your engine, on a normal day with a functioning radiator will operate around 200 degrees. The thermostat opens to allow coolant to begin to circulate from the warming engine to the cooling radiator, keeping it from overheating. A 160 thermo allows the process to start quicker and on an extremely cold winter day may not be advisable for quick warmup. You'd probably notice the difference most through your heater, which would NOT warm up quickly with a 160. Until later cars with their new smog junk and electronic brains, a 180 was almost always recommended by manufacturers- but for more complete combustion cars now operate up to 220, kept from boiling over by higher pressure caps and coolant, along with electric assist fans. Hope this is helpful.
 
I believe my car came with a 195 thermostat from the factory - hotter = more complete combustion (better gas mileage, better emissions, etc.). The ONLY time you want a colder engine is when making maximum HP, like on the track.

-Bob C.
 
Prior to emmission regulations most thermostats operated in the 160-170 range as this provided an operating temp that gave the best engine wear rate with a 4 to 7 psi operating system.
When emmisions became a priority, higher temp thermos in the 180-185 range were incorpotated with an increase in system operating pressures of 13 psi or more to provide a larger safety margin before boiling occurred.
Now most manufacturers are using 195 or more to achieve more accurate control of emmissions with system pressures of 20 psi.
An interesting aside to this is that for maximum power an engine operting temp of 180-185 is the best.
 
temp AND pressure

Yes, I agree with using the higher temp thermostat, but make sure you have a good high pressure radiator cap too. the added heat will generate more pressure that you need to keep in the radiator. you don"t want to boil-over!! I've always been told to use a 12-15 lb radiator cap. Not the 7lb ones...
The only other problem you might have is your radiator. Make sure it isn't clogged, it needs to be free flowing. have fun out there!:bgrin:
 
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Prior to emmission regulations most thermostats operated in the 160-170 range as this provided an operating temp that gave the best engine wear rate with a 4 to 7 psi operating system.
When emmisions became a priority, higher temp thermos in the 180-185 range were incorpotated with an increase in system operating pressures of 13 psi or more to provide a larger safety margin before boiling occurred.
Now most manufacturers are using 195 or more to achieve more accurate control of emmissions with system pressures of 20 psi.
An interesting aside to this is that for maximum power an engine operting temp of 180-185 is the best.

Very interesting. Here is my current understanding. Please correct if wrong:

The operating temp. the engine reaches is controlled by the thermal dissipation capacity of the cooling system (i.e. radiator), not the t-stat. The thermal dissipation rate of the cooling system being a constant at same speed, all three t-stat (160, 180, 195) result in the same operating temperature at constant highway speed -- over 200 at same ext. temp. Cold is below 110. The cooling system was designed to allow for temp to reach above 212 with the HOT light starting at 248. (Manual 120-49). Under average conditions, the t-stat does not change the operating temp of the engine at constant speed; it just changes the speed the engine temp. fluctuates and whether the engine temp stabilizes at the intended speed/usage. The t-start controls how temp. fluctuates and thus the thermal stress on your engine. The more temp variations the more stress = the more wear.

I read on a different forum that 160 t-stat is the preferred temp for Hotrod as it keeps the air under the hood from getting too hot too fast when doing stop-and-go, thus gaining HP (colder air) for sudden acceleration and then dissipating heat fast to prevent spikes. Because of the latency between time the t-stat opens (after the temp reaches the t-stat rated temp) and cooling system starts bringing temp down, the engine temp could have already reached 248 with a 195 or 180 t-stat. The sooner the t-stat opens, the smoother the temp spike, thus the 160 t-stat selection.

Hot-rods/performance mods are also likely to have new, more efficient radiators to keep the engine operating temp closer to 180-185 (see above). A 4 rows, high efficiency radiator from US Radiator, for example, may dissipate over 30% more heat than the standard OEM radiator. In mild temp of Oregon or low temp of Michigan winter, the engine would run around or below 200 with open t-stat. As a result, a 195 t-stat (opening at or above 200) and possibly a 180 t-stat would constantly open and close, resulting in constantly fluctuating temp (= thermal stress = no good). A 160 t-stat might be best in that case.

My understanding is that the Buicks were manufactured with a 180 t-stat as the default for average US temps/usage. The selection of the right t-stat depends on whether you operate the car in extreme outside temp (very cold or very hot), the thermal dissipation capacity of you radiator (OEM vs high efficiency) and your intended use of the car.
 
Thermostat controls ONLY the minimum temperature.

Ben
Ben, what does “minimum temperature” mean?

The thermostat only controls the temp (+ a few degrees) at which the water starts flowing through the radiator.

Then, depending on outside temp, acceleration/speed, oil (synthetic v. Conventional), coolant fluid and thermal capacity of the radiator (high capacity, electric fans?) the temp may settle above the opening temp of the t-stat, or fluctuate/cycle up and down around that value.
 
Another reason to use the specified thermostat is if the engine runs too cool it will cause sludging problems also, depending of course how much one does oil changes. A t/s rated at 160* is where it STARTS to open. Very rarely will a t/s cycle that fast from fully closed to fully open.
 
The thermostat controls the operating temperature of the system. The rated temperature is the temperature that the thermostat BEGINS to open up. It takes an additional 15-20* for the thermostat to fully OPEN, so a 160 stat is fully open by 180*, a 180* stat is fully open at 200*. An engine will not run cooler if the thermostat won't let it. If the temperature of the coolant runs more than 10-15* above the thermostat rating, the thermostat has lost control of the system. The radiator should have adequate heat transfer capacity to over cool the engine. As long as that is true, the thermostat will open or close enough to keep the coolant at the rated temperature. My philosophy is to get the biggest radiator you can, and then set the operating temperature with the thermostat. Aluminum radiators out perform brass copper radiators, that is why you only need 1 or 2 rows maximum. Aluminum radiators have bigger tubes, Brass copper is too soft to support tube sizes over 5/8". Aluminum can support tube sizes up to 1 1/2". More tube to fin content, more cooling. My nearly 20 year old Griffin radiator with it's 2 rows of 1 1/4" tubes keeps my 600 HP BBB engine within 5* of the 180* stat rating. If you have a 160* stat, and your engine runs at more than 180*, there is a problem with the cooling system, the thermostat is fully open and the maximum allowed rate of coolant flow is being admitted to the radiator, simple as that.
 
The thermostat controls the operating temperature of the system. The rated temperature is the temperature that the thermostat BEGINS to open up. It takes an additional 15-20* for the thermostat to fully OPEN, so a 160 stat is fully open by 180*, a 180* stat is fully open at 200*. An engine will not run cooler if the thermostat won't let it. If the temperature of the coolant runs more than 10-15* above the thermostat rating, the thermostat has lost control of the system. The radiator should have adequate heat transfer capacity to over cool the engine. As long as that is true, the thermostat will open or close enough to keep the coolant at the rated temperature. My philosophy is to get the biggest radiator you can, and then set the operating temperature with the thermostat. Aluminum radiators out perform brass copper radiators, that is why you only need 1 or 2 rows maximum. Aluminum radiators have bigger tubes, Brass copper is too soft to support tube sizes over 5/8". Aluminum can support tube sizes up to 1 1/2". More tube to fin content, more cooling. My nearly 20 year old Griffin radiator with it's 2 rows of 1 1/4" tubes keeps my 600 HP BBB engine within 5* of the 180* stat rating. If you have a 160* stat, and your engine runs at more than 180*, there is a problem with the cooling system, the thermostat is fully open and the maximum allowed rate of coolant flow is being admitted to the radiator, simple as that.

Well said, Larry. Well said.

Ben
 
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