Kenmohr, you've misunderstood my situation. I said: "I ran a 160 stat in a car for years". "In a car for years". Different car than my current car. My current car ('92) has a stock, 180 stat and with that, on this 104*F day, it was hovering in the 180's...so even in those temps, it's like I said; "down against the stat". If I installed a lower temp stat, it would likely run down against that temp...just like my other car used to with it's 160 stat, back when I had it.

Acids (and water) evaporate from the oil at higher temps -the don't "burn off". And realize that evaporation does occur at temps below 200* (or whatever your favorite oil temp is).

EDIT: I'm not recommending the use of a cooler stat...instead I'm simply pointing out that the world isn't going to cease existing if you run one, that it doesn't take an hour to warm your oil, and a reason why you'd run a 160 stat for someone who couldn't see a reason. It can work just fine.


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I run a 180 stat in my '85, and my coolant sits at...you guessed it...~180. A properly maintained cooling system will not have any problems even with a stock 195 tstat. Only reason I have the 180 is because that's what the parts store had on hand. If you're concerned about the operating temp of your engine, I highly recommend removing the radiator and giving it a thorough cleaning, as well as cleaning out the space between the radiator and the A/C. Those two things make a world of difference in the operating temp of the car-certainly more than a thermostat will.

As far as which tstat is best for performance? I wouldn't know that, but I'm actually more concerned with the life of my engine than getting every ounce of performance out of it-I plan on having this car for a while.

 

Tom, if you have a 180* thermostat in your 92 shown in the pictures, then I think your cooling capacity at those conditions is maxed out. You describe temps of 184-194. This is 4-14 degrees higher than the closing point of the thermostat. By default then, the thermostat is wide open and the temps are only controlled by the ability of the rad to get rid of the heat. In a hypothetic situation, putting in a lower temp thermostat will not allow the engine to run cooler under the same conditions described. Your race car was able to run at 160 because the radiator had the ability to take the temps that low. In past threads of this nature, you and I have both agreed that the maximum temperature an engine runs at is only controlled by the ability of the cooling system. The thermostat handles the minimum temperature.

EDIT: You are correct about the oil.

 

What makes you think it wasn't..........

fans come on around 228 bring it down to around 210,
195 t'stat....

 

For what it is worth, and I'm sure that ain't much, I was not looking to start anything negative, just asking a question. in my old knock around C10 with the 350 I always ran a 160 t'stat. I am simply seeking knowledge. I am not looking to change anything or looking for more HP. My C4 is a gem to me and a daily driver. I like to get on her occasionally, a burn out here and there and top her out. My radiator is new as well as t'stat. At highway speeds, she maintains between 198 and 204. When running hard, temps drop. In traffic, up to 228 and fans bring it back down to around 210. My oil does take about 30 mins to reach max temp, by that I mean the max temp that it normally runs which is around 190.
I have worked on cars as a hobby and as a necessity for about 35 years. So I must be pretty ignorant to not understand the concept that the t'stat keeps the engine from running below a certain temp. Because it is an internal combustion engine, it WILL not run at the ambient air temp. The engine creates heat that is controlled by the cooling system. I have owned cars that I removed the t'stat. The t'stat does not close at a certain temp, well it does, but it opens at a certain temp and allows cooler coolant, that has been cooled in the radiator, to circulate into the engine to bring engine temp down.

 

Its an equation where you consider the highest and lowest operating temperatures possible and consequences of each.

For the assumption that our fans/radiator is sufficient;
"If you are racing around a track and you have unlimited fans/radiator you can pick any temperature you want."

All that is left is for us to pick a temperature for our liquids and surfaces.
-engine oil is 205-212*F
Run the engine with 200*F and 215*F oil verify that it shows the same reduced pressure.

-coolant does not thin out like oil. Coolant cools the entire engine including heads. I will modify my head to ensure even heating at high output (1000-2000+ horsepower) as part of a list of necessary modifications. Part of "warning up an engine" involves warming the metal surfaces of the combustion chamber. The first time you get a push from fire, the surfaces are the same ambient temperature. As these surfaces warm up, the piston, the valve, the head, the deck, the gasket, the plug, each has an influence on the combustion event depending upon it's temperature. The easiest surface to modify is the plug because we can select from wide range of "heat ranges" which modify the rate at which heat is being removed. In a way, the plug replaces the coolant for that section of the combustion chamber, liquid coolant such as water isn't flowing through the plug so it can warm up to any temperature without our interference.

The "heat range" may or may not be comparable to a "thermostat". Heat ranges pretend to supply a rate for removal; whereas thermostat sets an exact measurable temperature for something to happen(water is on/off subject to flow). The plug "heat range" is more like a radiator, a heat exchanger of the ICE chamber. As with something that has a rate, the longer the combustion reaction is going on for, the more time we have to absorb and deal with unwanted heat that is being created. If and when it is created. The faster rate all the time means less efficiency- less economy when cruising and heat could be held in the chamber to participate in the reactions. Important feature if fuel use is restricted so worth the note. In a performance situation where there are no fuel rules, however, we always use the highest quality fuel (usually most expensive). The best fuel will achieve the slowest rate and make the most power throughout the expansion stroke of an ICE.

The coolant flowing through the head of the engine and the oil concerning the piston portions of an engine all will contain internal energy that has an influence on the rate and heat of the combustion. A very cold oil and cold surface could make it difficult to ignite some kinds of fuel. An 8-carbon chain as 2,2,4-trimethylpentane, (100 octane fuel), is less likely to evaporate at lower temperatures, evaporating with a slower rate to fill space. What we are trying to do is imagine our fuel evaporate in a very cold container. Imagine spraying fuel directly onto a 80*F Intake Valve. It will not bubble, hiss, pop, sizzle, immediately changing state to gas as it abosrbs the heat from the valve. Instead, it will puddle quietly there. Injector spray for engine starting and many OEM while running directly deposits fuel to the intake valve where it sits and waits for the valve to open, so it can spill into the chamber all at once and is not affected or deflected by injector spray issues at low pressure or low temperatures (when cranking voltage can drop in the cold, it must be considered by the manufacturer injector timing). It will also help warm the fuel by sitting on a hot valve in the other situations of normal driving. They want to ensure the fuel is hot before entering the chamber because OEM non-performance style driving might not heat the components enough to fully vaporize the fuel. Performance tuning usually involves moving injector spray timing for a more optimized performance and increased economy when fuel is injected to the open valve instead in some situations, and other small details of improvement. The point here is to realize that even something as small as injector spray timing or year of tech in question (DI engines do not get fuel, waiting on the valves) can affect the overall heat balance recipe of the combustion chamber, the plug heat range, quality of fuel, coolant temperature, oil temperature, piston materials, is a recipe. Often taking experimentation to find ideal circumstances. And sometimes the difference is negligible or impossible to notice. The engine thermostat dials up and down the temperature of the coolant surface portions of the engine head and block for our consideration, and like anything else, if we want to conserve the fuel the best we can, we would use the hottest plug, the hotter water, the hotter oil, until we hit the limit of the fuel we are restricted to. For example with 93, you can't start increasing plug heat range without immediately hitting the limit and blowing the engine apart, even in a stock application it could be disastrous. But in a cold climate for non-performance driving they are possible options for keeping more heats of combustion in the chamber. /post


which leads you to:
(Just like the thermostat decision could be heavily dependent on ambient temperature)
and an example:
Joe lives in a place where 12 months of the year it is always -30*F outside. He would be ridiculous to go from 180*F to 160*F. lol the very prospect seems ludicrous doesn't it? Add an oil cooler? You must be joking. Where do we think heat range is going? Joe needs to move.


Now he moves to a place where it is usually 80*F outside, but can go as low as 50*F and as high as 110*F.
It never freezes, so now he uses 100% distilled water. Water has the best heat capacity of any "coolant" and is safe to drink and spill, as required by many race tracks. The first time on the track it is 60*F outside and the sun is hidden behind clouds, the concrete and air is cold to Joe, there is wind and mists of rain. This is Joe's track so it is his risk driving it now. The engine performs flawlessly, oil stays cool, coolant sits right on the OEM thermostat at 195*F the whole time.

The next time he goes back, it is 92*F outside, the sun is in a cloudless sky. Joe can almost hear the concrete sizzle as sweat drips from everywhere. A/C is turned all the way up. There is no wind, and not much water in the air.
The car immediately overheats. In fact he hears it ping on the first stab. This is too much heat, especially with the A/C, for performance driving on 93 octane. If he put an amazing fuel in the car instead, say C16 leaded racing fuel was used, the engine might run well enough for him to not notice the insane overheat condition until a hose was blown from the engine to indicate that there was too much heat. The rate of heat removal from the engine depends on flow from the various coolants (oil and water mostly) flowing through the walls/crevices of the engine, and how quickly or efficiently the reservoir is able to remove any added, unwanted heat.
Again the trend is that sometimes heat is wanted, sometimes it is unwanted. We use thermostats to quickly trap wanted heat, then try to relief off the rest in real time which depends on efficiency of removal process. So to answer the thermostat question for both situations above, we can use common sense because these are very straightforward, and sometimes the actual situation isn't perfectly straightforward. I would say though that when fuel use isn't an issue (when stopping for fuel isn't "hurting me" costing time or money) the need to trap heat for efficiency declines rapidly to make performance situations far more ideal and easier to diagnose. For example having a low coolant temp and spraying water into an engine to cool the parts inside, while also seeing a very low IAT, being sure these temperatures are all nice and low would help me eliminate them as sources of problems in a combustion reaction when all of the parts in the chamber are nice and hot at a full output which is several times the manufacturer's original number. If I was also trying to get the best possible miles per gallon from the beast, I would need to "creep up" my IAT, coolant temp thermostat opening point, and of course not spray any water during cruise situations, blanket and thermocoat the engine, wrap all exhaust parts, radiate the heat from the bay the best I can but trap all the heat into the engine the best I can, to try an regain efficiency while also keeping WOT performance safe. The thermostat is just one of many ways to scratch the surface

 

The T-stat is not a binary device. It is a variable device so when it is designed to open at 180, it isn't closed at 180 and wide open at 181. A stat that is just starting to open at it's "rated" temp is not FULLY open until roughly 10* higher than it's rating/opening point. So, yes, My car is operating "down against the stat".

 

I'm glad that you asked. First, I never said "200 isn't". I asked you, "why 200"...since it was a hard number that YOU posted...right?
I was curious to hear your explanation for where that fairly specific figure came from. But lets go ahead and examine this anyway. For LT1 cars, the stat is designed to start opening at 180*F. So we can go ahead and assume that 180 is the lowest Temp GM was willing to run the engine and still meet all of their criteria. If you're driving the car on the highway, it's going to run right around 185 the entire time...see my post above for proof of that. So we could say that "GM wants it to run around 185".

I DON'T say that, however, because what happens when you are running at low speeds/idling or in traffic? No air flow temp starts to climb...where does GM cut it off? Right around 230* when the fans come on. The fans drive the temps down to ~217 and shut off. So going by that we could say that "GM wants it to run around 224" -in between the fan on/fan off temps.

So which is it? Does GM want it operating around 185? Or 225? That is a whopping 40*F range and 50* when you consider the max ranges (bottom of the stat and top of the fan range).

In the end, there is NO "perfect temp" and as has been stated earlier, our criteria is not the same as GM's they have to care about stuff that we do not. So...the "perfect operating temp" is the one, or range that meets each of our individual criteria.

 

Unless you have the Bowtie logo tattooed on your pecker, one needs to decide for themselves instead of asking WWGMD.

 

It sounds like it's working fine and I'd leave it. The potential that a lower temp stat offers for more power are two fold:
1. lower intake manifold and head temp = lower air temp (denser air).
2. additional timing advance due to cooler head/inlet temps.

I think #1 is marginal -probably not worth anything meaningful. #2 is where it's at. If you can add a couple degrees of timing....AND your engine is capable of exploiting that timing...there is where some meaningful power is found. In the pursuit of that, any degradation in engine life is also, IME, meaningless and not worth wizzling about.

 

I can buy some of that but I also don't agree you would be "down against the stat" if you were to change to a 170 and apply the exact same conditions as your data shows you are at times in the 194 range.

 

Say what? Where did 194* come from? If I were to change to a 170 stat I'd bet I'd be running in the mid 170's range. I know this b/c I've done it already, on an older car with a 160 stat.

Note that the temps were 104* when I took that pic. That is about as hot as most of us will ever see. The point is that even under that heat, I'm still "right there", at the stat.

As far as "buying some of that"...why not test it for yourself! Go tie a string on to a stat, drop it into a pot of water w/a thermometer in it. Gradually increase the water temp...How does the stat open? Like an on/off switch? Or gradually, like a variable valve? You'll see.

 

 

What do you mean? I tried to address your comment a couple posts above. Did I miss something?

 

The 194* comes from your statement in post #18.

"My coolant temps read (on the DIC) 184*F - 194*F. Here is where it was at when I first noticed the temp and snapped a pic...."

Whatever...

 

Lots of true info here. Now pick the one that best suits you.

 

This has been discussed a lot and no-one seems to have the same opinion. I tend to agree with Tom.

 

-And the best part about these T-stat threads; nobody knows how to provide the proper (°) symbol

 

In contrast to other threads where numerous people don't know how to spell, use capitalization, periods and proper sentence structure. Text-talk seems to be the norm and no one seems to have a problem with that. Which symbol do you think takes less time and effort to type, * or ° especially for those who have stated their keyboards do not have a numeric pad?

 

I get it. You think that my coolant going 14* over the T-stat cracking point is proof that the stat has no control or influence on operating temps. For the seconds that it was above about 190, you're right. For that brief moment, in 104* ambient temps, with the AC on, the coolant temp was outside of the realm of T-stat control.

Conversely, I feel that this particular example is evidence that supports my point; that the cooling system should be able to drive coolant temps "down against the stat" most all of the time. I feel that this example supports that b/c even in 104* ambient temps, with the AC on, the temp was mostly down in the range where the stat is regulating flow and thus op temp. My point is that the conditions were borderline "extreme".

So we obviously interpret the data differently, but I can tell you from experience that with a healthy cooling system a lower stat will typically result in lower op temps. 104*F ambient temps isn't typical, IMO.


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