180 ... or 195 ?
 

How many of you use 180 degree thermostats or 195 ?

I'm leaning toward 195 as specified originally. I assume if my cooling system is operating properly it should not go over 195, which is fine to me unless someone tells me otherwise.

It's 68 AC car, and the AC probably will be getting used. Stock engine.

Anyone know what temp triggers the idiot light switch?

And .... why is the freakin hole in the thermostat about 1" ID while the hoses would flow about five times that much?

OK,have to be diff,I use 160.Tom

Does it actually run at 160? Or settles in somewhere higher?

my 62 GP runs at 160,so does my 69 455 bird.Tom

I used a 160, but engine ran at a steady 175.

160

160 here too. Runs between 175-185.

195°F with 10W30 is a perfect match.

Running a 160°F thermostat plus heavier oil looses power and increase engine wear and reduce fuel economy.

I have found no reason not to follow recommendations in the Owners Manual.

Idiot temp lamp turns on at 245-250°F.

FWIW.

I run a 180..and drove guys in the staging lanes crazy as I idled my car to keep it up on the thermostat. Consistent temp, heat soak makes for consistent passes. ;)
I need a 180 or my heat is meh.

What compression ratio did you end up with? Time will tell if it likes heat.

Like the others, I too run a 160 in several of the cars here.

Depending on how good the cooling system is dictates whether that particular car will actually run 160 though. Plus ambient temps here in the SW desert are much higher than most other places in the country. Pushing the compression ratios, the crappy 91 octane we have out here on the West coast are just some of the reasons why I prefer to try to keep the engine a bit cooler. Been pushing them like this for 30+ years. Excessive engine wear and poor gas mileage is not an issue at all. Some of these engines have been together for 20+ years now without a single issue, and everything I have returns respectable gas mileage for what it is.

Another 160 user here. I have been using 160 degree thermostats for 25 plus years in my Pontiacs.

I would run a 195, but with iron heads it's hard enough to control ping. I figure a 180 stat is a good compromise


I guess this raises another opinion.

if I had aluminum heads, 195 would probably be the route i would go.

I’d love to hear from some engine builders on this subject , in regards to the cylinder wall wear rebate on too Cold a stat . I built an iron headed 10.1 406 , zero decked with a 280/288 bullit roller and otherwise stock cooling I.e. 4 core Harrison and stock 68 flex fan . Should I start out with a 160 and go from there ? I’m just assuming a 195 will cause detonation . What has been other experiences ?

160 for me in 3 cars. The only with mechanical gauge says it runs 160-165. Would buy another 160 again.

I run a 195 with iron 96 heads. This question is just like “what oil should I use” or “what color should I paint my car?” You’ll hear everyone’s opinion, and just have to come up with one of your own.

^^^^^ that’s why I’d like to hear from experienced engine builders and such . Was sludge an issue from running too cool ? Experiences on the dyno such as different bsfc etc .

Never had any sludge type issues at all. I feel that issue is more related to the oil you use, how often you change it, and whether the oil has a good detergent package.

If we still had 100 octane at the pumps like we did 45 years ago, I probably wouldn't be so concerned with engine temps and cylinder pressures. If I weren't pushing the pump gas envelope with the crappy pump gas we have now, I also again, probably wouldn't be worried about engine temps and cylinder pressures. I'm the type of street guy that will build the engine to push what I can out of it with the given pump gas we have to work with. Others just want the engine to run and get from A to B with little concern how much power it makes, some even want to run the cheapest gas they can find. As long as it idles smooth and makes vacuum most here are happy. Those types of engines probably don't care how hot they are running.

Everyone will have a different situation.

Yep, collecting opinions.

Mine is an iron head (16), right at 10:1.

In the past I've run 180 for the simple reason that it gives me more head room should something be amiss. ... If the cooling system is working the way it should, the temps should be no higher than 180 ... if it goes higher, you know there is a problem. If I start with 195 and something is amiss .... it might be at 205 before it become very evident. Less time to do what you have to, to get things cooled down.

But ... I imagine the radiator works pretty good at 195, the higher the Delta T between coolant and air temp, the more efficient the heat transfer. My guess is the OEM radiator is designed around an average temp differential that includes 195 degree coolant. But lots of people don't run original radiators now. Coolant formulas have probably changed also.

I think I'll start with a 180 and see how it behaves.

180 with an aluminum radiator

Experiment with it. If it's a 10:1 iron headed motor, then engine temp is definitely something I'd pay attention to. 180 may work fine for you. Tune up, the pump gas quality, and the camshaft (cylinder pressure), rear gear, trans, and weight of the car all play a roll.

There are a couple of mine here that I run a 160 in but the car doesn't actually run 160. One example is my 69Z, it has it's born with date coded radiator, a copper 3 core, and completely stock cooling system, clutch fan, shroud etc... It's an 11:1 iron headed motor I'm running on pump. Engine temps run right at 175 degrees most of the time. Throughout the summer when ambient temps here were over 100 degrees the engine would run in the low to mid 180's, which isn't all that bad really. The only time I've seen it run just under the 170 range is early morning cooler temps.
Basically this cooling system just isn't capable of keeping this engine at or near 160 when ambient temps are in the normal daytime range here. But hovering around 175 works in this case. However it's certainly not an engine I want to force to run at say 195 with a 195 stat.

The trick is to run a 205 thermostat for the block, and a 120 thermostat for the cylinder heads.

Good luck with that...it's possible (I suppose) but extremely inconvenient.

It's an auto ... which adds some heat, AC which adds some heat, 068 cam, 2.93 gears (should help). Back in the day ... cruising around in Memphis on a hot day it never seemed to have much of a problem.

I'll be using the radiator out of a 68 lemans, 350, AC, Auto ... hopefully the same unit as found in the GTO. I think a different code, but same basic radiator.

When they recore these radiators .... do they/can they use copper like the original? Can the original copper cores be tested/restored to original level of function?

How many cores in that radiator? I'd be looking for a 3-core. Four core if the ambient temp is often high. I've made it a point to install the largest radiator that will fit the rad support, including removing a block-off panel on my Toronado to install a radiator several inches wider than OEM.

Another issue is that radiator cores can have a high or low air fin count. The fins per inch are not guaranteed to be the same as the original equipment. It costs less to build fewer fins per inch. OTOH, there are "high efficiency" cores that have more fins per inch than OEM.

Original cores are unlikely to be usable after all these years and miles. Even if the water tubes can be de-scaled, the air fins may still be rotted. We see some of that in vehicles that are subject to salted winter roads--the salt-water mist kicked up by the car in front corrodes the air fins of the radiator of the car behind. If the air fins are not solidly attached to the water tubes, the radiator can be "clean" but not cool worth a crap.

Plenty of folks would suggest a new aluminum radiator. QUALITY aluminum radiators are a blessing. Cheap Communist Chinese aluminum radiators are...less recommended.

Your radiator shop can guide you.

In my case it's going to have to be exactly as OEM as far as the tanks go, and of course the physical size of the radiator will have to be the same. From what I'm seeing a copper/brass recore is going to cost about the same as a QUALITY US made new copper radiator.

Right now I have a "BI" code radiator out of a Lemans .... proper code is "PB" for a GTO with AC and Auto. So I may end up having to find some "PB" tanks at least ... I'll have to do some research to find out where to go. Basically I want the most cores as I can stuff into the proper size tanks. Pretty sure an Auto, AC, GTO used the biggest (most cores) radiator available that year (68).

Until I go pull it out of the shed I'm not even sure if the code letters were tagged to the radiator or stamped into the tanks, I'm just referring to my notes.

My engine will see 190 to 210 degree oil temps and 160 degree or under coolant temps if I let the engine cool down enough at the dragstrip when I make a pass.

Is it as simple as measuring the thickness of the core to determine the number of rows on an OEM radiator? Is it indicated anywhere on the exterior of the radiator?

I do have an example here that is "BI" code, and has a "4" below it. But seeing as it's from a 68, 350, auto 2bbl, AC ... I'm thinking it maybe a 3 row. Well ... come to think of it I could probably just look inside the hose connections :)

You can see the holes of the flews just by looking into the filler hole. You'll see them at the top. Might need a flashlight if your lighting isn't good. So for example, if you see 3 holes across, you have a 3 flew, 3 row, or 3 core, whichever you want to call it.

All of my everyday driver vehicles have had the 195 thermostats and a/c and have never had a cooling issue in Michigan.
We get a few hot days, not like Tom S in Cali.

The 64 GTO, (owned forever) has always run a 180 degree thermostat. Lived in Missouri for several years (Hot days and Cold nights many times.)

Never have run a 160 Thermostat because, if I was worried about too much heat in the Engine/ Radiator, I always ran a restrictor ring and dialed in the temp I wanted to see in the engine. I was always wanting to remove the moisture in the engine (OIL) quickly. Water is H2O.
None of those elements are good with liquid petroleum products in engines for bearing/crankshaft loads.

Tom V.

my 455 activities get 180, no mechanical coolng fan. Still in dumbass mode on this one, but the iron heads seem to burn clean.

160 in the summer and 180 in winter. Temps don't usually fluctuate too much. Will reach 205 if I'm stuck in traffic a while on a hot summer day but normally runs right wherever the stat opens.

http://www.stant.com/index.php/engli...s-thermostats/ . Interesting , but left me with a few questions . So your 180 isn’t fully open until 195 or so - so is 180 - 200 really the exceptable temp range for the 180 ?

Interesting .... I just got their "super stat" which apparently opens sooner and "throttles" the flow more so than a conventional type.

If at stat started to open at 180 it would probably depend hugely on the performance of the rest of the system how close it would get to fully open at 195.

I think thermostats do the opposite of what most people think. They don't keep temperature down to their rating, they keep temperature UP to their rating :) Otherwise you could use a heater core for a radiator and put in a 160 degree stat :).

In other words ... they can keep your engine at 180 degrees if your system works well, but they can't keep it from reaching 250 if it doesn't.

I think the purpose of a 180 degree stat is not to make sure your engine runs DOWN at 180, from a design standpoint it's more to make sure your engine runs AT LEAST 180 .... if you take my meaning, as they are designed assuming your cooling system can handle whatever load the engine is capable of producing.

That is true. 180 is the opening temp for the stat.
Full open is not necessarily the right position for the stat to be in anyway.
Just like air conditioning in your car, you don't want max A/C all the time,
you want the a/c temp to be right for the conditions. same with the engine
cooling.

Tom V.

160 but runs about 180 under current conditions.

Ok then as mentioned above , 160 but runs at 180 seems like a capable system . I’d rather run a 180 myself but think I’ll start with the 160 just to see where it’s at with my iron heads & 10.1 comp

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.

X2, 160 works great!

So for all of you guys that run a 160° Stat, Do any of you have oil temp readings running below 180°F coolant temps?

My oil temp will read 190/195 down the highway at 60 to 80 mph..if I take the rpms up a bit more it will rise to 210 and in town oil temps will go up to 210.
This is a "hardblocked" shortblock I'd assume a non hardblocked shortblock would stay cooler at lower driving speed and possibly higher highway speeds?

"Ideally" you want your oil temp above the vapor point of water, to remove condensation from the crankcase. But where you pickup your oil temp from can greatly vary the temp readings.

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.

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.

.

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.

thermostat
 

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

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.

thermostat
 

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

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

'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.

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

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?