160 vs. 180 thermostat what the differance?
 

This is from a post I place on the FE forum because I having a temp problem which prompted me to ask the following:

On the subject of 160 vs. 180 thermostat I'm not sure I follow the logic. A 160 will open sooner however, the engine does not continue to run at 160. Most will continue to increase in temp to around 180-185 I would guess. A 180 will not open full until 180 however, both the 160 and the 180 are open full once the engine is at operating temp which as I said I believe is normally 180-185. Plus, most electric fan thermo switches turn the fans on at 195+ so the engines would seem to always exceed the 180 mark and the thermostat should always be open full.

So,What is the benefit of running a cooler thermostat?

Thanks,
Mike 'monster'

Your onto something. Well it does offer a "cushion" of 20 Deg before "boil over". Not that a big a thing, must be something more than that to it! OK, how 'bout lower engine temp keeps incoming air charge (to carb) cooler and more dense, offering better performance? Well,,,route your air cleaner so it gets cold air anyway and you still haven't gained much with a 160. Lets see........ The motor requires a richer mixture at a lower engine temp, thats for SURE. Wait, is that a benefit? Don't think so! Oil stays cooler? Hmmm,,,not sure thats a "good thing", more sludge build up becomes possible at lower engine temps.

All this ASSUMES of course that the engine temp will actually FOLLOW the t-stat temp! It could, regardless of your fan t-stat setpoint. At "speed" you may not even need the fan at all. When you DO need the fan, the temp "curve" will follow the fan t-stat setting NOT the engine t-stat setting. So make you fan t-stat ALSO 160 if that's what you want!

I got fuel injection, I'm going with 195 myself. I think HOTTER is BETTER!

Ernie

Mike

I like the 160 for several reasons. Mine opens so that the car can run at about 170-175 on the road. I turn my fans on manually when it's hot outside--and it'll stay at 185-190 in stop and go in Fresno summer heat for a good while. Obviously, if it gets too hot in stop and go--it'll keep climbing, but as Ernie suggests--the lower temp to begin with gives me more room.

10 degrees isn't going to do much to the carb mixture or oil life or cleanliness.

Been running mine like that for quite awhile--ran my cars in the 60s and 70s the same way--no long term problems.

Monster,

With adequate airflow through the radiator, a 160F thermostat will keep the temperature 20F lower than a 180F thermostat. When you are depending on the fan for airflow things are a little different. The temperature may be dependant solely on the difference between the ambient air temperature and the engine's. Once the engine temperature goes above 180F, both thermostats are fully open and you are getting maximum flow. Below that, the thermostat will "throttle down" the flow to match its rating.

An engine has an operating range where lubrication and fuel mixtures are optimum. Running with the oil too cool will allow water and fuel condensates to build up, plus oil flow will be reduced to many critical areas.

Last year I was running a 160 in my 351W. Ford Racing advised that may result in some increase in power . They also advised the 160 WILL cause more wear on the motor for reasons stated by Bob Putnam. I suggested the new synthetic oils may have superior lubricating properties. They convinced me that engine longevity was the issue and it had to do with oil temperature.

That being said--I noticed only about a 5 degree drop in my oil temp despite the change to the 160 thermo for the coolant. So it may depend upon the engine and setup. I'm not sure there is a direct correlation between coolant and oil temps--yes, they affect each other, but certainly not degree for degree.

No question that too cool a temp, or too hot, can affect engine wear. Coming from a farm--alot of idling, heavy loads, working in extreme heat and cold--I know this to be true. But where are those limits and how do they apply to particular motors?

For example, is my Cleveland (10.5 to 1, lumpy cam, etc.) going to be affected the same way as a Windsor? Or an FE? I do know modern cars, electronically controlled (to prevent detonation) as they are, are designed to run at hotter temps (using synthetic oils to allow for it) for smog purposes as much as anything else. Having used my 92 Vette in the California desert for business purposes (drive, park, go, idle, etc.), I certainly got to expect 220-235 as "normal". This was with the LT1 motor with reverse coolant flow which was created to get the coolest coolant to the heads first--why?

Maybe the 60s/pre-smog motors can benefit from a 20 degree coolant drop while it may not be a good idea for Windsors or other modern motors. Again, with a 160 thermo, my motor does not run at 160--it runs at 170-175--is there going to be damage? I have to wonder since synthetic oils were first created for military use to deal with freezing temperatures as much as extreme heat.

Alot of conflicts in information--anybody got some answers?

Second opinion
 

This topic has come up a couple of times in the past. Most folks seem to opt for lower coolant temps and the "extra pad" it allows before overheating. However, it is useful to consider that the internal engine components are designed to operate at a specific stabilized temperature. To that end, the parts are machined so that when the parts heat up during combustion, the thermal expansion of the components achieved at stabilized temperature establishes the proper clearances between moving parts. This web site:

http://216.239.33.100/search?q=cache...hl=en&ie=UTF-8

discusses, among other things, the relationship between stabilized coolant temperature and cylinder wall wear. Notice that at 70 deg C (about 158 deg F) the cylinder wear is significantly higher than at 85 deg C (about 185 deg F). Admittedly, the study is on tractor engines, but the principle is the same. Most of the earlier engines were designed to run at about 185 deg F coolant temperatures, and the later ones run at close to 200 deg F (to reduce emissions). Running at significantly lower stabilized temperatures could result in accelerated cylinder and ring wear, due to increased mechanical clearances and dilution/contamination of the lubricating oil with fuel blow-by. IMHO, it's better to get the cooling system running properly and at a constant temperature than to pad the temperature margin running lower than normal temperatures.

I know that when I had my 95 Mustang GT running a 180 degree t-stat vs. the stock 195 allowed you to dial in a couple of degrees more timing. In that car more timing (to a point) equaled more HP. I know on really hot days (Texas) when the engine temp crept up it was much more prone to pinging.

JB

Jamo if your normal engine temp is around 170 to 175 and your "carbed" I wouldn't loose any sleep over it, ha ha.

Hey, it's not like the Cobras are going to see 100K miles. You will get "bored" with the motor long before that kind of mileage comes up and swap it or re-build it anyway!

Might be a different story with your "tow" vehicle now! I'm EFI, I think my motor will run "better" and live longer at 195 than at 160-170.

Ernie

Okay,

After the post I started thinking some more (alway a dangerous exersize for me) and I started wondering about the "throttling affect of the thermostat. From what I'm hearing this does occur and so the result is that though a 180 thermo is open at 160 it is throttled back (restricted) and not fully open. A 160 at the 160 is open fully. With the same flow of ambiant air over the radiator which will only have an "X" degree cooling affect on the radiator say 10degrees @ 70 MPH, a 160 thermo running at 170 degrees temp would run at 180 degrees or so, while the 180 thermo would run at 190 or so. This would be due to the ability of the radiator to only disapate 10 degrees at the ambiant temperture with the same air flow across it.

So, if this logic is correct I can now see why a 160 thermostat can reduce the running temperture below that of a 180. Heat disapation being a constant in a cooling system (it can only disapate so much heat), the lower the "full flow" setting of the thermostat the cooler the system should run.

NOTE: this would be true to a point since some restriction is required to allow for the heat disapation in the radiator, running without a thermostat can increase the running temp by not allowing the coolant enough time to transfer heat while running through the radiator.

or am I totally off base or do I pass this test??????????:confused:

Thanks,
Mike "monster"

Mike, this is an involved subject, but a "simple" (hopefully accurate) synopsis is this:
A given cooling system can only cool to a certain temperature under a given set of conditions. If the system could only cool to 195 degrees on a given day/speed, etc., putting in a thermostat with a lower rating would only open the t-stat at the rated temperature, allowing full flow, and take longer to reach 195 degrees. If your system would cool to 165 under those same conditions and you put in a 195, you could watch the temp gage rise to 195, the tstat would open, the temp would try to drop to 165, the tstat would close, and the temperature would start rising again to 195, then keep rising and falling as the tstat opens and closes. The tstat won't lower the running temperature, it only helps warm the motor up to its opening temperature quicker, for efficiency and longevity. The system will then run or try to run at whatever its steady-state capacity will allow for the given conditions.

Running a tstat is strongly recommended by most...if you run without one, you should put a restrictor in its place, so the block is running under pressure flow, and to eliminate steam pockets and hot spots throughout the block. I've heard of some instances where taking the tstat out actually promoted boilover due to steam pockets and hot spots.

Ken, I think we are almost saying the same thing however, by you own example the tstat is controlling the running temp. The 195 is trying to keep the system at 195 and the 160 is trying to keep the system at 160. The opening/closing of the 195 will keep the system at 195 and NOT allow it to run cooler however the 160 is trying to stay at 160 and not throttling, so the temp can stay at anywhere from 160 up. If the disapation of the system allows it to run at 170 it will/can stay there, the 195 system will always want to go to 195 and stay there. A cooler tstat can affect the running temp...................if this is correct. (we are talking about summer conditions 80+ degrees and not colder winter conditions)


Now for an added twist, Are there different size openings available for tstats ? To small of an opening would seem to cause excesive restriction and lead to a higher runninig temp.
(Ken I like your tstat abrv. easier to type)


Thanks,
Mike 'monster'

Mike, you're right, in that the 195 system will try to keep a system no cooler than 195...if it wants to run at 175, it will cycle near 195; if you put a 160 tstat in the same system, same conditions, the 160 tstat would open at 160, and the system would keep slowly warming up and stabilize at 175, the temp it wants to run at under the assumed conditions. The 160 is trying to keep it at no less than 160, the 195 is trying to keep it at no less than 195...and a cooler tstat can affect the running conditions, but only if it replaces a tstat rated at a higher temp than the motor wants to run at. If the motor wanted to run at 140, both the 160 and the 195 would keep the motor running at a higher temp than the temperature it wanted to run at.

On your other question, I'm not sure if there are different i.d. openings; I know for sure there are some tstats with a larger o.d. than others...had to get a BIG'un for my FE. I'm guessing there would be some slightly higher running pressure in the block with a smaller tstat opening, but not sure if it would make a great difference in the running temp.

As an interesting aside, (for the colder temps in the winter), BMW always had the standard tstat on the motor outlet, but a few years ago Car and Driver reported that they started putting another tstat on the radiator outlet on cars sold in Germany. Seems that the coolant got very chilled at higher speeds (autobahn, etc.) and cycled into the hot block, causing a few cracked blocks. Not sure how putting the extra tstat at that point would allow the radiator water to ever warm up, though!

Interesting about the BMW radiator stat! Removing the stats (plural) in the heads of a Jaguar V12 WILL result in over heating. Not just sometimes, all the time! I found out the hard way and have owned several Jag V-12's since then.

Hmmmm,,,,,,put a Jag V-12 in a Cobra...a bloody english marriage there 'eh what?

Ernie

Looking at this again
 

Well... I'm looking at this again myself. 180 vs. 160.

Just took a drive this evening, the cooler air is setting in now. I read everyone's posts here. The one that has me thinking the most is Bob Putnam's.

Here is a thought I'm pondering. I adjust my valves when the motor is hot. The motor runs well when its hot, valves sound right, all is well. This evening I'm on the freeway crusing along with my 160 degree thermostat, check the temp, and I'm running 163 degrees. Seems great, however, I can hear the valves a bit more. "Initial" throttle response is okay at 163, but not the best. Then run into some traffic, motor starts to warm up again, reaches 185 degrees, and wallah! Better throttle response, and I can barely hear the valvetrain again... Went back and forth with this paying close attention and it seems there is a sweet spot, and running my FE too cool is not good either. I was very focused on more carb re-jetting and tuning, but realized it may not be necessary if I can figure out how to keep the motor at optimum temperature for the majority of my driving.

I think I'm going back to a 180 thermo for the winter months for sure. Any thoughts?. My motor just seems to run better, crisper, responds better once I get to 180/185; not to mention the wear considerations, clearances, and oiling design issues mentioned above. It seems to me that just 20 degrees difference does have a noticeable impact on my FE.

Has anyone else noticed this too while running a 160 thermo on those cooler driving days with their FE?

Controling temperature
 

Dear Monster,
And every one else.
Please correct me if I am wrong but every one seems to be missing a very important point here.
Monster you say you run your thermo fans at 195F.
If you do this the thermo fan will control the temperature of your emgine at idle and low speed like in heavy traffic.
The thermo fan should come on at a temperature lower than the thermostat being used.
I run a 180f thermontat and have the fan come on at 170f.
If the thermo fan comes on higher than 180f then the thermostat will fully open and as there is no air going through the radiator and the temperature will continue to climb until the thermo fan kicks in.
I live in Australia where it gets DAM HOT in summer and I have never had an over heating problem.

Regards,
Bryan

lots of reference articles on the web...
 

... just finished reading several test articles on running a 160 vs. 180+ thermostat.

I think I'll definitely be going back to a 180 for that optimum operating temperature during the colder months; not to mention all the things that were brought up about premature wear and loss of performance, carbon buildup, acid buildup in oil... when the motor is running too cold - when using a 160...

Duane,

If an engine ( like mine) wants to run hot , there is "0" advantage to a 160 t- stat , I posted about this a few mos. back as I was concerned about the constant fluctuation of temp between 160 and 200.......since I put in a 180 my temp is much more stable 180 to 190 tops ! and as you noted, engine performance is also stabilized.

I hope your motor likes the change as well as mine did,

KK

Thanks.
 

KobraKarl,
Thanks.

180 it is, with a small hole drilled per ERA's recommendation too. It all makes sense now...

I guess a good way to look at it is to think of the the thermostat's job as being to limit how COOL the engine runs not to limit how hot it gets. That becomes the function of the radiator and fan(s). The thermostat is there to limit the effectiveness of the cooling system until the engine approaches the upper end of the ideal operating temperature range. If your engine has an overheating problem, no thermostat regardless of how low it's set to open will help. If your rad and fans are inadequate, the temperature will continue to climb as long as the engine is running. If your cooling system is efficient, however, the thermostat will stop it from cooling the engine below that optimum temperature range.