ghostrider20

I have noticed a few topics on cooling systems. I have run 160 degree thermostats in my chevelles and my corvette and found them to be great.
I took the 190 out and replaced it with a 160. It runs around 175-180 while driving and then during idle conditions (or making it through the burger drive up with 10 cars ahead of me) it will take about a half hour in extreme summer conditions to get it around 220. My theory was if it starts at 190 degrees or 200 degrees it does not have much further to warm up to get to temps that effect the carb etc. From Mec. Eng. school, "heat transfer", at idle and a constant RPM, heat will increase isobaric over time, or at a constant rate.
Is this thinking backwards, my cooling system is good, but I have heard that mid-years have temp problems from the factory???
-More-Info- I am confident in the cooling system, it is all new as of 2 years ago, but things change in 2 years. (I will check it again). I ran a few cycles of water through this summer to flush it out and it ran clean both times. I have a Raytech Ranger I use to check the temp at different locations on the radiator. I flows and is transferring heat well. I understand how the system works, if I have a 160 installed and in runs at 175-180, the thermostat is open all the time. I find when driving around town, while the car is moving, the temp stays at 160-180. Then when I am in heavy traffic and in idle conditions, I am just "buying time". Although I don't have a cooling problem, I was under the assumption that 180-190 is the optimal range. I have blocked off the exhaust heat crossover in the manifold and after that I think I could go back to a 180. I was always told that a cold intake charge is a good thing, but heat is a large part of fuel atomization, were is the fine line here?
NOTE- I don't have a cooling problem, The max temp I have ever seen was 220 degrees and the car had been idleing for about 45 minutes and the outside temp was around 98 degrees. This is not abnormal, I was just under the impression 180-190 was ideal at all times.
Always open for opinions and advice.
Thanks.
Mark

65 nassau blue 327/365


[Modified by ghostrider20, 1:39 AM 2/7/2002]


[Modified by ghostrider20, 12:41 AM 2/9/2002]

davo32

ghostrider, I am also now ( after my recent rebuild ) running a 160 thermo in my 67 and have similar heating and cooling attributes.

I was actually a little concerned that in the summer months, when the air temp is much higher, that I might get into a overheting situation.

When I ran a 170 thermo I had a pretty consistent temp and my cooling system seems to me running normally ( stock water pump, new hoses, clean and rust free rad, new thermo and pure coolant without water ).

To be safe I was considering a small pusher electric fan to keep my radiator a little cooler.

Kid_Again

...well, this is probably duke's area when you're talking about isobaric changes, but from the trenches, imho, the issue of corvettes overheating is due to the fact that the cooling systems are not in good operating condition...EVEN in the 60's, if the general had that many problems with overheating, they would have had a serious business issue - and they sold every car they could make.....when you say, in good faith, that your cooling system is good, how do you know?...for example, i've learned the hard way that flow testing a radiator means nothing because you're not measuring heat transfer - the simple solution to any overheating problem with these cars is a new or recored radiator, good system flush and maximize airflow over the radiator core....

...i've always wondered about 160 vs any other temp tstats and the advice i've heard (quality unknown) is that you want the engine to get up to operating temperature as soon as possible (i believe 180's were installed at the factory) to maximize the engine's efficiency and to help ensure vaporization of the charge mix....dunno, but others here will.........i think 220 on a hot day is too hot...with a crummy radiator, virtually non functioning clutch drive fan and the A/C on, my big block got that hot only once, detonated like hell, at which point i did a complete cooling system rebuild and it never again went that high......your issue may not be the thermostat


[Modified by Kid_Again, 6:24 PM 2/6/2002]

62fuelie

The 160 thermostat is too cold. The engine needs to run at 180 to insure that crank case contaminates are boiled off. If you have a 160 thermostat and your engine runs at 170 or 180, your cooling system is deficient, either in size or condition. The thermostat is just that- a thermostat. It should limit engine cooling to a predetermined temp.

pittsaj

The idea here is that the thermostat conrols the flow of water into and thus out of the rad.
Water is cooled in the rad and the longer it stays there, the cooler the water entering the engine will be..

By lowering the temp at which the thermostat opens, you are also causing the water to flow more quickly through the rad. Therefore less time to cool.

One would think that removing the thermostat completely would cause the engine to run it's coolest.. Wrong, the water will flow so quickly that the engine will actually run hotter.. No time for cooling in the rad.

If your cooling system has enough capacity with a 180 thermostat your radiator will be able to keep the beast cool with BTU's to spare..

I tried every trick in the book.. All to not...

Would run 200 and 220 with the AC

I changed the rad..
Got a new Dewitt's
Temps way down...
Runs 180 all the time 190 at very long lights with the AC on
I don't watch that gauge any more

If you are runnig hot now, You need to look closely at that rad..
Mine looked like new but was, well crap.

Tony


[Modified by pittsaj, 4:20 PM 2/6/2002]

magicv8

What I read about Corvette thermostats is preAIR (smog pump) SB engines all got 170 degree thermostats. AIR got 195. After 1970 all got 180.

396 RAT

I tossed mine altogther. Some will boo hoo me,
but I have a stock solid lifter 425 that runs 170-190
all the time now. Stop and go trafic, whatever.
Unless it freezes where you live is it a concern IMHO.
I only drive it above 60 deg. Tried all kinds of stuff,
then got fed up and tossed it. Not for everyone I know,
but it works for me.
Fire away! But I m running coooool........

SWCDuke

I recommend that you convert to the OEM spec 180 degree thermostat, and run a 50/50 water-glycol mix. This will yield a boiling temp. of 265F with a 15 psi cap.

Engines run better when they are hot. The higher the temp, the less tendency there is for blowby to condense in the crankcase. Also, Chevrolet has been telling us for about 30 years that higher cylinder wall temp reduces friction which yields more power at the flywheel.

An L-76 with a proper functioning cooling system, including aluminum radiator and fan clutch should not overheat, but 220-230 in hot weather while idling is not outside the design limit.

Check your distributor number. If it's the early one, swap out the vacuum advance can with the one that had all the vacuum advance in by 8". This was a running change on '64 SHP/FI engines that carried over to '65.

I tried blocking the heat riser on my '63 SHP engine, but it resulted in a stumble until the car had been driven for at least 20 minutes. I finally just swapped the heat riser valve with the FI spacer, and it's okay in mild weather.

If your engine runs okay with the riser blocked you can leave it be, but if it stumbles or hesitates at light throttle, take out the blocking shims and just wire the valve open.

Duke

0Tom@Dewitt

I've always preached that thermostats get way too much credit for their role in cooling. From drilling holes and changing to different temperature values it's all just wasted time. If you missed it, read Pittsaj above again. He tried everything without success, then changed to the stock aluminum radiator, problem solved. The reality is that only one component removes heat...the radiator. Yes there can be some slight improvements with tricks like high flow water pumps, timing, fans, etc but if you don't have enough radiator, your just pissing in the wind. My agruement on thermostats goes like this:
Take a cooling/heating system in a house for example. The furnace/AC is big enough to heat/cool the house without running continously. It cycles on and off because it is actually oversized to do the job. The wall mounted thermostat simply turns the furnace on and off. Now if your home AC was set to 70 and the AC ran continously but couldn't cool it down, would you replace the thermostat? Of course not, that wouldn't change anything. Well the same thing goes on in a car. The radiator needs to be greater than the heat load the engine can produce. The mechanical thermostat should modulate to maintain it's setting. If you are ever running at a temperature over the thermostat, that means you are giving it all the water you got and the radiator can't remove it. Here's more on the subject: www.dewitts.com/pages/whyaluminum.com

Kid_Again

.....imo, clearly not being an engineer, i'd like to hear from some of the data-types about heat transfer issues.......from an intuitive standpoint, it seems logical that the radiator (as the name implies) is the most critical component for heat dissipation....but, you would think that the function of a radiator is dependent on, among other things, the temperature of the inlet water and it's velocity (higher velocity to me would mean less residence time and less time to transfer heat)....given that, it would seem to me the function of a tstat is pretty important but maybe the differences are not meaningful when one compares a 160 vs 180...though, i may go to a 180 after giving it some more thought.........if i had to go with one key componenet, i suppose it would be the radiator :confused:

TheOman

"By lowering the temp at which the thermostat opens, you are also causing the water to flow more quickly through the rad. Therefore less time to cool."

I don't think so. Changing to a 160 only changes the point at which the water starts to circulate. It does NOT change the rate at which it flows. Think a moment. A thermostat is only an opening and closing mechanism that determines at what temperature water from the engine enters the radiator. Put a 160 then a 170 then a 180 then a 195 stat into the same engine with no other changes. How can the rate at which the water enters and leaves the engine and the radiator change? It can't cause the pump is the same in all cases. The pump determines rate of flow not the stat ( given that all my hypothetical stas are capable of flowing the same amount of water at wide open condition) so tell me how the 160 allows more water flow??????

All the stat does is regulate the point at which the water starts to flow thru the system, the radiator determines the amount of heat transfer capability in degrees per unit of time and the stat opens and closes in response to the water temp being supplied to it by the radiator and engine.

Why is it that we all want changes in thermostats to fix cooling pronblems? The answer to getting rid of more quantity of heat is more ability to disperse heat to the ambient surrounding air. You gotta pass more air thru the rad (at a temperature cooler than the water) or you gotta have a radiator that can disperse a greater quantity of heat into the same volume of air flow. You gotta flow more cool air thru the same radiator or get a bigger radiator if you want to transfer more heat. My experience has never been that a change is t-stat temp will change the operating temp of an engine that is already at the margin of the cooling systems ability to disperse heat generated by the engine.

0Tom@Dewitt

I don't want to hog this thread with my opinions but this subject is my profession, it's what we do for a living. Kid_again, I used to subscribe to the "too fast water" theory and that's part of the problem with cooling stories. Most of the information you get is someones "theory" but most of my comments come from customers experiences. Not one here and there but hundreds. You are so very right about "other factors" being important in solving cooling problems. There is a considerable amount of engineering that goes into a cooling system and all too often we speak in general terms about an engineered system. A doctor wouldn't prescribe a medication unless they asked several details about the problem yet when someone complains of over heating many are quick to offer a sure fix. A perfect example is the fact goastrider20 doesn't even state what kind of radiator was installed two years ago, brass or aluminum. Considering we had them both tested and the brass performed 30% less that the factory aluminum, this is a major item to consider. Coolant mixture is another often misunderstood item. Water cools, much better than anti-freeze however I know many people assume that if 50/50 is not good enough. Now I'm not saying run 100% water but rather consider the freeze protection you actually need and mix accordingly. I have seen where 30/70 drops the running temps by 10-15 degrees. Air flow is another factor in the formula but it should not be a problem unless the radiator isn't doing what it should or the engine is what I call a heat generator. The bottom line is that there is no one answer for everyone. Way too many factors involved in cooling to even list here and multiply that with the different possible applications, ie big blocks, small blocks, C1,C2, C3, creat motors, .060-.080 over and the list goes on and on.

joevette57

One thing I don't think I've read in this thread, ( though I read it kinda fast) is this. The thermostat on our Vettes is not like that in our homes, on or off. (duh) A 160 stat
STARTS to open at 160. It's not fully open till about 185-190. That's why a car with a 160 stat will still usually run at a higher temp. When I had the 180 stat in my 65 temp ran consistently at around 205. With the 160 I run about 175, 185 with the A/C.
I agree with Tom though about the radiator. I'm going to swap mine out a new aluminum rad before we get into our Fla summer heat.

Kid_Again

...ok, let me again try to 'splain my question....i understand that flow rate is not dependent on the postion of the stat (unless it's closed) - it is dependent on the pump speed (volume would be dependent on both, i assume)...i suppose i do believe that an aluminum radiator is more efficient than a brass one, all other things being equal (based on marketing hype that i've seen, so i'm still a bit skeptical..haven't seen the comparative data - my brass recored bb radiator works just fine, thank you - no need to over engineer, as i've been quite rightly told).....

...so, if all my assumptions are correct, assuming an ideal cooling system, how do you get the most efficiency out of a radiator???......to put it into a practical question, i would think that the fluid residency time (and surface contact) in a "good" brass radiator is very important (for heat dissipation) so that one wouldn't need to go to a high velocity water pump or a 'spensive aluminum radiator if everything else was "in spec"...all this is independent of tsat temp setpoint....no????

0Tom@Dewitt

Kid_again, I just got more confused. Please state what engine (bb or sb) and year you are currently refering to and what type of radiator you have in the car now. Then I might be able to help with some of your questions. td

396 RAT

Here's what I do. If its running hot, poopie can the thermostat.
If it still runs hot, buy a new rad.
9 times out of ten one of the above will solve the problem.
Its not rocket science. If your rad is flowing too slowly (clogged)
Give it more flow. If added flow does not help. The Rad is too far gone.
Its the same with all heat exchangers. IMHO thermostats were designed mainly
for areas where it gets butt cold. Period. Dont think too much into what they do. I will get hammered on this post. But this is what I have found to be the truth.

pittsaj

We've all been through this at one time or another,
These threads always draw alot of attention..
That's because our cars are 35+ years old.
Most of us are running should I say warm...

Guess you can do whatever works for you..

Most go through the same routine as below:

Lower stat setting,
Higher stat setting,
No stat,
50/50 antifreeze mix
No antifreeze,
Water wetter,
Better shrouding,
New fan clutch,
No fan clutch,
Aux fans,
New Rad

You can always put a resistor in line and crank in whatever temp makes you happy. :lol:

Bottom line is,
If your rad is in good shape you will run cool.
If it is marginal, well nothing is going to work.

Good luck

Tony


[Modified by pittsaj, 10:01 PM 2/11/2002]

Kid_Again

...actually, neither of my cars ran "hot" once i recored the big block brass radiator, swapped out the small block's original aluminum radiator with a new one and thoroughly flushed the cooling sytems - i plugged up the radiator shroud where possible and went to direct drive fans as a precaution.......so i don't have a problem.........perhaps i can ask it this way, on EITHER car, would i get an incremental benefit if i went to a high volume water pump for the street?...radiator residency time would go down but volume would go up so i wonder if that tradeoff is worth it...does that help?


[Modified by Kid_Again, 6:19 AM 2/12/2002]