[dataway]

Originally Posted by Formulajones

Correct. It's often misconstrued. The stat rating is where the engine temp will be at or higher. Depending on how efficient the cooling system is. As in my example above, it never runs 160, the original cooling system just isn't capable. I find most of my cars here with copper radiators, even the 4 cores, aren't capable of that (but they are slightly better). However I have 2 with Griffin radiators that can keep the temp closer to 160, even under high load conditions, still using the stock clutch fans and shrouds.

It's all going to depend on how well the rest of the system works.

Yep, what happens is that with a 160 degree thermostat, and an excellent cooling system, on a 90 degree day the Delta T between coolant and air is only about 70 degrees. Hard for a radiator to make use of such a low temperature differential. It's not that the system can't handle it ... it's that it's not ENOUGH for the system to handle efficiently, so the radiator will let the coolant increase in temp until the Delta T is sufficient to remove the same amount of heat that engine is adding in.
Same reason a household AC has a hard time making cool air on a hot day (not enough Delta T across the condenser), or a heat pump trying to pull heat out of 20 degree air.

[HWYSTR455]

I run 180 stats, and use the spring type, not the turn-to-open kind. The two cars I have the most recent experience with run at about 185.

One was hard blocked half way, the other not.

Oil temps are the key I have always been led to believe, and moisture removal was the desired effect. But, once you shut down, you get a spike, and chances are pretty good that there wouldn't be much moisture left after 30 min or so, even if the oil is below 212.

You do get a slight boost in performance from lower intake charges, so crossover design comes into play. Too cold though and fuel can puddle, and not vaporize as well/quickly. So guessing it's a fine line.

Climate where you live plays a part, so again, guessing, it will kind of 'depend'. Best thing to do is try different temp stats and use what works best for you.

Curious comment regarding timing change relationship with endplay. Makes me think harder about it now that it's been elated that it may not change that much.

.

[Squidward]

Both of my engines use a 180 standard Tstat. Both run a 4 core Champion. On my FB, I ran no tstat for a while to see how it would do. It never went above something like 157, and in the cooler months less than that. So I knew I had excess capacity. With my a/c on, it would bump up another 5-10 degrees.

[68 Firebird]

I agree with above posts. If the cooling system is optimized for the load, then
you will only see temp raise a few degrees over rating of stat. Trust me my
car was not optimized when I first got her on the road. Now she hangs within
a few degrees of stat rating even on hot days.
-running a hotter stat now and can tell she likes being a tad warmer.
-Severe Duty fan clutch, 2 row rad with one inch tubes, clearance WP and
8" crank pulley with 6.5" WP pulley.
-All baffles upper and lower are inplace, along with firewall seals
-trying a Motorad stat with a rating of one ninety two. Closest I could find
to a one ninety. so far she does not budge the gauge off one ninety.
-I will say it warms up and is snappier quicker then with the lower stats.

No answer is wrong here, just like oil and spark plugs. everyone will have a different
experience.

Gerry

[dataway]

How to you like the Motorad? Haven't had one in my hand. The Stant "SuperStat" seems decent quality.

Weird with stuff like that... a nice thermostat is like $5 ... I'd be willing to pay $10 for something of stellar quality .. but I guess there just isn't a call for something like that.

[68 Firebird]

THM 192442
bought local from Napa for 4 bucks.
buddy is using them and had good stable results in a few classics.

[dataway]

Interesting .... slightly difference design than others I've seen.

[Longs]

'67 GTO with 400 YS engine, A/C car with auto and 3:36 posi rear, with Desert Cooler 4-core radiator, factory shroud and clutch fan. I run a 180 thermostat, car will stay between 185 - 190 around town but on extended highway drives on a hot day with hills, temp will get up around 210 on a Stewart Warner mechanical gauge. I would not in any way say that I have "optimized" for cooling efficiency.

[glhs#116]

You 160 guys just lack commitment. Let me tell you what folks do out here in the blowing sands of Arabia. The first thing any genius roadside mechanic does to any car that so much as slows down in front of their shop is to fill the radiator with plain water and throw the thermostat in the trash.

I have a Chrysler minivan 2002. This thing has been through the blazing centre of Oman down to Salalah and back with my whole family and pratically everything that could possibly be stuffed into it. AC cranked, foot to the floor, 120 degrees plus outside temps all day. That car never budges even slightly off the centre of the gauge once warmed up and it never has. Earlier this year I let a friend borrow it for a week. She had an issue with it not starting and took it to "her" mechanic. The guy replaces my top radiator hose with some Chinese garbage piece and, sure enough, removes the thermostat. Yeah, thanks buddy! At least he had the decency to leave the removed thermostat in the car to save me having to source one myself.

My GMC Suburban with the big 454 is my desert rig. I drive it hard in the worst worst heat and humidity. Factory radiator, factory fan clutch. I never could get it running smoothly. Then, one day, it hit me. I took off the thermostat housing and sure enough, good old Doha missing thermostat. Ordered a new one and stuck it in. It's like a new engine. Purrs like a kitten. Still never overheats.

My 1971 Trans Am has the factory 197 iron heads, factory intake with the factory exhaust crossover. Clutch fan, factory shroud, BeCooler radiator. I run a 195 thermostat because that's what it's meant to have. Does it ping, even when it heats up a little? No.

As others have said, there are really only two possible outcomes for running a cooler thermostat:
1. The cooling system is sufficient to the engine's needs and so the cooler thermostat will successfully run your engine too cool. Combustion will be less efficient, wear will happen faster and the oil will probably not get hot enough to cook the contaminents out of it like it should
2. The cooling system is insufficient to the engine's needs and so the cooler thermostat will fail to maintain temperature and the car will overheat. Incidentally, exactly the same thing that would happen with the correct temperature thermostat or no thermostat

Sam

[Formulajones]

Originally Posted by glhs#116

My 1971 Trans Am has the factory 197 iron heads, factory intake with the factory exhaust crossover. Clutch fan, factory shroud, BeCooler radiator. I run a 195 thermostat because that's what it's meant to have. Does it ping, even when it heats up a little? No.


Sam

Those engines were lucky to have 8:1 compression. I wouldn't be worried about that one pinging no matter what the temp.

I'm going to take a stab at something and guess you guys out there probably have higher octane gas without all the crap additives that we have here?

[dataway]

I did once have someone tell me that removing the thermostat can actually cause an engine to overheat because the increased flow rate and turbulence reduces the systems ability to transfer heat, as the components, passages etc. are designed to operate within a particular flow rate range. No idea if it's true or not.

[MD79TA]

I hope this is not perceived as a high jack but , I have been running a 195 degree . In hot summer days I worry as temp seems to climb over 200 and level off. Still no over heating issues with 91/93 octane and iron heads at 9.4 comp, The question for me is what brands are most running for the 160/180 thermostats? I know there is alot of overseas junk .and failures. Any good USA made ? Who? And where to order ? . Doug

[glhs#116]

Originally Posted by Formulajones

Those engines were lucky to have 8:1 compression. I wouldn't be worried about that one pinging no matter what the temp.

I'm going to take a stab at something and guess you guys out there probably have higher octane gas without all the crap additives that we have here?

It is probably a minimal additive package since the Petrol supply is now a state monopoly (Woqood). When I first came here there were a couple Shell stations still and you could tell the difference (same stock, of course, but the Shell additive package). But that was long ago. Probably just some stuff to stabilise it for the heat...

Sam

[Squidward]

Originally Posted by dataway

I did once have someone tell me that removing the thermostat can actually cause an engine to overheat because the increased flow rate and turbulence reduces the systems ability to transfer heat, as the components, passages etc. are designed to operate within a particular flow rate range. No idea if it's true or not.

More flow = better heat transfer. The rest becomes a proportional arrow analysis of heat transfer coefficients and Tins/Touts.

[glhs#116]

Originally Posted by dataway

I did once have someone tell me that removing the thermostat can actually cause an engine to overheat because the increased flow rate and turbulence reduces the systems ability to transfer heat, as the components, passages etc. are designed to operate within a particular flow rate range. No idea if it's true or not.

I think this is one of those shadetree myths. As someone pointed out on a different cooling thread, if you look at what the factory did in every case where higher cooling capability was called on, they took steps to increase coolant flow and increase airflow across the radiator (and/or increased radiator size).

Think about it this way: Whether the coolant is moving fast in the engine or barely moving there is always *some* coolant adjacent to any given piece of metal. The difference is that if you don't have enough flow you might get too much heat into a given "chunk" of coolant before it gets a chance to cool off in the radiator.

Or think about it this way: If the coolant didn't move at all the radiator would always contain really cool coolant (ambient, pretty much) and the engine would just heat up until it melted. At the other end of the scale is where you have coolant moving so fast that coolant temps in the engine and radiator hardly differ. At this point it's just a straight-up battle between how much the radiator can cool and how much the engine can heat. All slower coolant flow gives you (eventually) is a bigger temperature gradient between the radiator coolant and engine coolant. Since the coolant in the radiator gets cooled based on the differential between radiator coolant temperature and ambient air temperature you get best cooling with the highest radiator coolant temperature for a given (same) engine coolant temperature. That means you want this differential between engine coolant temperature and radiator coolant temperature to be as small as possible. And since you already know what engine coolant temperature you want the way to get there is by reducing this differential with more flow.

Sam

[dataway]

Originally Posted by Squidward

More flow = better heat transfer. The rest becomes a proportional arrow analysis of heat transfer coefficients and Tins/Touts.

Were you a nuke? Seems like I remember a couple on here.

I think if you'll recall your formulas ... more flow = more heat transfer (all things remaining constant), not better transfer. Transfer coefficients are based on materials used, medium of transfer and type of flow (laminar or turbulent). But yes total heat transfer in the sink would include Delta T and flow rate.

So, if an increase of flow changes a turbulent flow in to laminar, you could have a lower transfer coefficient. And if T-in is so low that the Delta T between heat source and heat sink are too small transfer efficiency can suffer depending on materials used etc. Not to mention possible aeration of the coolant which does bad things to heat transfer coefficients.

T-in and T-out are used to calculate total heat loss through the heat sink when combined with flow rate and btu/lb-ma of the transfer medium. Actual transfer coefficient calculation for the whole sink would have to take into consideration surface area of the heat sink, flow type, material coefficients, corrosion layers etc.

From a practical standpoint, yeah, ((t-in)-(t-out)) x flow rate(lb-ma) x btu/lb-ma would give you the total heat loss through the exchanger. But only in a perfect system. If flow rate alters flow type, or causes aeration, etc. it's not always a straight line relationship. And material thermo-conductivity changes based on temperature. Also radiation heat loses increase with temperature.

Every system has an ideal flow rate and Delta-T that it is designed to operate within. If flow rate was the only consideration .... all any system would need to be a better system would be bigger and bigger pumps. Usually the heat sink has to be matched with the heat source. Remove a thermostat and it's possible the temps could go down. It's also possible the heat sink would be incapable of lowering the temps beyond the designed limit ... such as 180 degrees, and also possible a flow rate which the system was not designed to handle could reduce the efficiency of the entire system. Also possible the radiator would be incapable of using the extra flow.

I would say it all depends on the particular system in question. Might cool some vehicles down, might make others run hotter.

Don't make me get out my Heat Transfer and Fluid Flow notes .... I still have them you know Class of 7801 (Instructor at M.A.R.F. 79-82, Kesselring Site, NY)

[Squidward]

Yes. And by better, I meant more.

I understand, then, I am preaching to the choir.

You have me by over a decade. I was an instructor in Charleston. I had the chance to run "OMG end of the world" events on the computer sim equipment they installed there. It took a full semi trailer of computer gear to run the physics for that thing. Now they could probably run that simulator with a cell phone. But I digress!

[GRX]

180 stat here. Older Stant brand. Have a few saved up.

Std bore 400, iron heads, 11-bolt pump, stock four core radiator, stock 7-blade clutch fan about one third way into the shroud.

Stewart Warner mechanical temp gauge tells me it tops out around 185 regardless the conditions - below freezing or sitting in traffic at 95 degrees.

[#1965GTO]

Well if your temp gauge is actuate you will see temps over 195. I threw away a VDO mechanical gauge that would show 15-20 degrees higher than actual temp. I replaced it a SW that is much better. In hot weather you may see 220-230 especially at idle. That's not great but not unusual. For all of the Pontiacs I've be associated why the factory cooling systems are marginal at best. The lower temp stat won't help to keep it cooler but just open sooner and not allowing the radiator time to do the most good. There is a whole thermal science related to this theory. The 1" hole in the stat body acts as a restrictor intentionally to slow down the coolant and give the radiator more time to cool it down. There is a lot pressure generated by the water pump so the hoses are sized for volume, pressure and suction. There are tons of technical discussions on this exact topic. The bottom line by most "experts" say the state of engine tune is a very important factor in maintaining a desirable running temp. I used to go for the high volume stats and still ran hotter than I like. I finally conceded a went back the standard stat with the 1" hole and dropped several degrees on our hot days. Here in southern Nevada when it's 120 outside you better have a well tuned cooling system especially around town. You know all those little things like the rubberized material around the radiator and shrouds, well GM didn't millions engineering this stuff to have them removed or deteriorated, these details all mater.

[JFMetter]

This is interesting. I started a thread over in Heating and Cooling TECH (Getting the Therm Housing off a 389 Tri-Power) that ended up talking about t-stats, with ZeGermanHam advising me that t-stats are not magic bullets with regard to cooling a motor. Since I was upgrading a broken water pump with a FlowKooler pump that's supposed to help cool off the motor (with increased coolant pressure and flow) and AMEs suggests using a 180 t-stat with this pump and I had a 195 in the motor, I got to thinking about t-stats. A 195 t-stat will keep the motor at 195 or above. 195 is the lower limit on how cool your cooling system can make the motor run at. Even if the system has the capability of driving down the motor temp to let's say 185, you'll never see that on the motor with a 195. A 195 is closing as the operating temp drops below 195 so the temp will start raising back up till it opens the t-stat at 195 (and back and forth). So if you're happy with your motor cooling, even with the air on, then going to 180 might be just fixing something that's not broken. But it sounds like you're a bit concerned about engine cooling? Asking what temp the temp idiot light trips (by the way, get yourself a laser temperature thermometer - $20 bucks or so all over the place, Amazon..., and you can get the real temperature right off the running engine block, say at the temperature sensing plug area)? If that's the case the t-stat can't help you. You can even pull it and it will not help out. You need to do something else to affect cooling - a shroud if you don't have one (and sealing the edges to create more of a vacuum air flow), or a different radiator, or more ify things like a more efficient water pump/fan clutch/coolant liquids. Then if you do that and want to see this change drive the cooling below 195, a 180 t-stat makes sense.