what determines the correct thermostat for your engine?

[jerry S]

What is the "rule of thumb" in deciding whether to get a 160, 180, or 190 thermostat?

 

[69Rcode_Mach1]

I don't know of any rule, I just went with 180 because that is the typical operating temp you want.

 

[66HertzClone]

I'm not sure there is a rule, I was using a 180 stat until the EFI was installed. It requires a 195 to operate correctly, I can see the gauge reflects the higher operating temp since the change.

Remember that the stat opens at that temp and closes if the coolant should get below it. It is likely that the engine will not stay at that temp, operating conditions, and other components will decide how hot or cool the engine will run.

A higher temp thermostat will allow and engine to stay cleaner inside, the higher temps will cook off any condensation and keep the crankcase cleaner in the long run.

 

[oz]

On a 'warmed up' non daily driver (both carbed and fuel injected), I go with 180 t-stats. The main reason I see is that the lower engine temperature slightly reduces the risk of detonation. Another thing to consider is that with more power, you have to disipate more heat. The extra room between 180 and boiling helps reduce the instance of overheating.
That said, with a stock engine, use a stock temp t-stat.
Never use a 160 degree t-stat. That is just too cold to keep an engine clean. Anything fuel injected will stay in 'warm up' mode... not good.

 

[Hack]

Higher engine temps also reduce cylinder wear.

 

[rbohm]

higher temps improve wear, fuel economy, and drivablity, cooler temps improve power. i usually run a 180 stat on a carbed car, and 195 on efi cars. i have run a 160 stat on a carbed car that had detonation problems that couldnt otherwise be cured, but i dont like doing that. also in southern az i will run a 160 stat in the summer with a marginal cooling system.

 

[krash kendall]

Don't be confused. A thermostat only controls the minimum operating temperature of the engine, not the maximum temperature.

 

[DJCarbine]

I switched to a 160* Tstat recently because I am running 14 degreen initial with about 44-46 total timing advance. I figured the cooler temp would help with detonation problems. I also noticed a power improvement with advancing and re-curving my timing and going with the 160* tstat. Cylinder wear goes up with the lower temp Tstat, but I find that my operating temp still stays around 170, and never is below 165

 

[67coupe351w]

Don't be confused. A thermostat only controls the minimum operating temperature of the engine, not the maximum temperature.

Maximum temperature is a function of engine power output, radiator size, and ram air velocity (among some other things like timing).

If a car had infinite cooling capacity (uberly large radiator) the engine would run at T-stat temp (+/- a degree or 2) always.

 

[D.Hearne]

Not all T-stats will keep an engine at the rated temp of the T-Stat. Use the one that keeps it closest to the temp you want it at. On my 89 Ranger, a 160 degree stat keeps the engine around 190-200.

 

[Edbert]

I'm glad OZ said it. You can easily run too cold for your own good if you don't pay attention.

Also, ignore everything except steam if you have a factory gauge

 

[84convertablegt]

I have a rebuilt slightly warmed up engine (289) in my 65. I couldnt get to car cool enough with a 180 and a stock rad. I switched to calibrated 160 from Mr. Gasket and still ran hot. So I got a griffin aluminum and problem solved. My 160' tstat has proven to work well, it is definately not too cold for my car. I usually run right at 160 on a cool day but on the hot days I run up to 180-185, so using anything higher than a 180 would put me into a not so happy zone for me. On my 95, I run a 180, but only because I have a SCT chip to turn the fans on sooner, etc. EFI cars are much more sensitive. Like D.Hearne said, use the one that keeps the car running where you want it at. The rating on a t-stat is only when it will open, not what it will run at, unless your radiator/fan combo is super efficient.

 

[65ShelbyClone]

I have a rebuilt slightly warmed up engine (289) in my 65. I couldnt get to car cool enough with a 180 and a stock rad. I switched to calibrated 160 from Mr. Gasket and still ran hot.

That just proves that if the cooling system is incapable, then a properly functioning t-stat has nothing to do with overheating.

I used a 195 in my '89 GT during winter and when I needed to smog it while the rest of the time I used a 180. I noticed no difference in economy, but the gage of course read ~15 degrees different between the two. A margnal fan clutch was to blame for the hot weather cooling problems I had, but a flex fan and Summit radiator kept it locked on 180 in August with the A/C on full tilt.

With that said, a cooler thermostat has never solved any cooling problem I ever had. 180 is the lowest I would go except for a dedicated drag car.

 

[2nd Mustang]

http://autos.yahoo.com/maintain/repairqa/fluids_heat_air_conditioning_general/ques019_2.html

I have a 160 in my warmed over 302, with a four row radiator and stock water pump, flex fan and no shroud. It averages around 170-180 on normal days and near 190 during summer. I can feel the performance loss at 190 as opposed to 170.

 

[67coupe351w]

Not all T-stats will keep an engine at the rated temp of the T-Stat. Use the one that keeps it closest to the temp you want it at. On my 89 Ranger, a 160 degree stat keeps the engine around 190-200.

Most likely your radiator is not sized correctly to cool your 331.

Another option is the T-stat is mislabeled or malfunctioning. It goes back to what I said in my previous post. If you have an infinitely large radiator your engine will run at T-stat temp always.

Since none of us have infinitely large radiators (but rather close to properly sized..usally on the small side) our engines will run around T-stat temp a good amount of the time (mild weather, mild driving, ect.) until our radiator capacity is pushed to its limits...whether it be from ambient temps increasing during the summer (some noted their cars run hotter in the summer than winter) or from driving like a bat out of a very hot place (making your engine produce full power, more power = more heat).

It sounds to me from reading the above posts that the best rule of thumb is this:

160 = band-aid for under-sized radiator.
180 = good for carbed vehicles.
195 = good for EFI vehicles.

 

[D.Hearne]

Most likely your radiator is not sized correctly to cool your 331.

Another option is the T-stat is mislabeled or malfunctioning. It goes back to what I said in my previous post. If you have an infinitely large radiator your engine will run at T-stat temp always.

Since none of us have infinitely large radiators (but rather close to properly sized..usally on the small side) our engines will run around T-stat temp a good amount of the time (mild weather, mild driving, ect.) until our radiator capacity is pushed to its limits...whether it be from ambient temps increasing during the summer (some noted their cars run hotter in the summer than winter) or from driving like a bat out of a very hot place (making your engine produce full power, more power = more heat).

It sounds to me from reading the above posts that the best rule of thumb is this:

160 = band-aid for under-sized radiator.
180 = good for carbed vehicles.
195 = good for EFI vehicles.

I'm fully aware that the radiator in the Ranger's too small, but it's all that will fit. Also why I posted what I did. Run the one that lets the engine run closest to what temp you want it at. Not all cooling systems are equal or up to the demands you put on them.

 

[65ShelbyClone]

It sounds to me from reading the above posts that the best rule of thumb is this:

160 = band-aid for under-sized radiator.
180 = good for carbed vehicles.
195 = good for EFI vehicles.

That's a good way to put it.