cor72vette

I'll be replacing all my hoses :smash: on my 72 350 this weekend since the weather's going to be poor. What are the members thoughts on going without a thermostat? The car is driven only through spring to fall. The reason I ask is, back in the day when I was building my 71 351C Pinto, it was common practice not to use a thermostat. My Vette on the other hand is not treated with anything but the best care.


[Modified by cor72vette, 11:17 PM 5/30/2003]

Corey_68

Well without the thermostat the water moves too fast through the engine and doesn't allow for proper cooling. If nothing else run a 160 dgree thermostat and drill 2 small holes in it. I've often seen cars run hotter without one.

:cheers:

Cookwithvette

A properly operating coolant system should have a thermostat. It keeps the coolant at operating temp, nothing more. The faster the engine gets up to temp=less wear/longer life. Like Corey said, if you're concerned about keeping cool in a really hot climate a 160 should be good. Nothing wrong with a 180 though. Hole drilling is best for cars not using the bypass hoses. Remember, heat makes horsepower, that's why nascar guys actually try to keep their engine temps in the 200s. ('course running 200+ on a street car would be mighty uncomfortable. :lol: )

redvetracr

Hopefully there are "Autozone" parts stores where you live. They sell the Robertshaw brand (priced right too!!) I run a 180. ...redvetracr

cor72vette

Here's a question; what size hole and how many do you drill?

turtlevette

Even if your car is not driven in cold weather, it needs to come up to operating temp quickly to avoid cylinder wear.

69vette66

I use a 180 and have one 1/8 hole drilled in it. I have never seen it above 180 yet.

:cheers: Larry

Rockn-Roll

Allow me to enlighten you as to thermal transfer rates. In college they teach that increasing the flow rate will increase the amount of heat that the system can remove. It also makes sense to me, hopefully I can help you see this too.

Let's say you take a thin piece of semi-hot metal (just hot enough to make your finger a little red...nothing too painful except this lesson) and hold it with your thumb and finger......ow right? But, if you keep holding onto it (you are brave right?) the metal will quickly cool down so that holding it will be no big deal, but the metal will still be warm even after 15 minutes because the transfer rate slows down as the temperatures of your fingers and the metal begin to equalize. Well, let's say that's like letting the water sit in the radiator...the transfer rate starts out quickly, but slows down as the water sits because the water and radiator temperatures get closer to each other.

On the other hand if we took a long hot metal strip and moved it through your fingers (you are willing to bet your fingers on this right?) then if you are correct then the transfer rate will decrease? Of course not...and the faster you move that strip through your fingers the larger the difference between the temperature of the hot metal and the temperature of your fingers (though your fingers will get plenty hot).

Well, anyway I hope you get my point. The point being that thermal transfer rates are proportional to the difference between the two temperatures, so just as soon as the water hits the engine the water heats up and the engine cools down, and thus the transfer rate decreases because the temperatures are now closer to each other.

This is why it is desireable to increase the flow rate of a cooling system. But, keep in mind that the coolant is not the only facter in our system. The air flow must be considered too...there is a point where increasing coolant flow will not provide reasonable gains (though it won't hurt except to tax the engine more by driving the water pump faster) without increasing the air flow through the radiator.

As for the thermostat in or out...I have been running without one for 20 years on every car I own ever since one of those $5 POS finally failed to open and destroyed a head gasket and warped a head, got water into the oil and spun a bearing...total rebuild was required. Also punched a hole in the radiator from the pressure (radiator isn't supposed to act as the exhaust manifold).

Rockn-Roll

Cylinder wear is due to the lack of oil on the cylinders when the engine is first started and has nothing to do with the temperature of the engine. Heat itself is a catalyst to wear. If it was economical to keep the cylinder walls like -273 degrees centigrade (the coldest possible temperature) then engineers would be designing them that way to avoid wear...well...at least the engineers that get A's in their field of study...the engineers that get C's (those that get only 50% on their tests) will probably design them however they are told to do them, or whatever would be popular at the time.

SanDiegoPaul

C'mon now this is VERY basic. An engine needs a thermostat. Period.

VegasJen

wish i could agree with you paul but i just don't. an engine needs some heat in it just to help cook off any condensation in the oil pan. i agree heat is an enemy to an engine. it is not necessary for the engine to run correctly. just imagine if it were possible to design an engine that could operate at ambient temperture. we would not have to anticipate piston slop and ring gaps being correct for the thermal expansion, we could just build an engine to be as efficient as possible right in the shop. i've heard the same theory about water moving too fast to pick up heat but i just don't buy it. as long as your not cavitating the water pump (then your not moving enough water), you will have heat transfer. thermaldynamics say the greater the Tdelta, the faster the cooling media can absorb heat and faster the generator can reject it. i say as long as the pump isn't cavitating, you can run without one just fine. air pockets are what prevent cooling, not too much water.

Desertdawg

Even out here in the Arizona desert, at 115 degrees, you better have your thermostat in, or your going to cook your motor. :mad

norvalwilhelm

You need to operate your motor at above 185 degrees. Gas does not atomize properly below this temperature and we don't want washed cylinder walls. Also I have seen wear charts and a motor operating at say 160 exibits 4 times more wear then a motor running at 195.
I believed in running a motor around 160 most of my life but in the last few years I have changed my mind and now like to see the temperature gage around 190. Nascar does run their engines hot, as high as 230 to produce the horsepower. They also run them lean.
To operate properly and have a long life the motor must be hot enough and lean enough.
I'll bet that 75% of the older carburated cars are running too rich to produce maximum horsepower.
That said I don't run a thermostat in my vet, everything else but not the vet because it quickly comes to 190 without a thermostat, I do not operate it in any but warm days and I find after shutting down for short periods the heads equalize the temperature quicker without a thermostat.
For most cars I recommend a thermostat.

turtlevette

Rockn-Roll,

I agree with you that increased flow rate must by the laws of thermodynamics provide a cooler engine. Its an old wives tale that taking the t-stat out will cause a hotter engine. No way, its impossible. You are correct on your therory there.

I disagree with you on running as cool as possible. If you talk to engine experts they will tell you that running an engine too cool will cause increased cylinder wear. The explanation Norval gave is correct of course! This was one reason for going to the reverse flow design on the LT1 engines.

I used to run my Grand National without a t-stat and jumpered the electric fan to run all the time. It ran stronger because the intake charge was not heating up as much in the intake manifold, providing a cooler denser charge. Thats why they put ice on the intake in drag racing, it acts like a half azz intecooler. I sold the car so, i didn't have first hand experience on the longevity of the engine but was sorry i had done that after getting more educated.

If you are going to run your engine at 160, at least use a lightweight synthetic oil so you get the proper viscosity at that temperature. I'm convinced heavier oils will not be "thin" enough at that temperature.





[Modified by turtlevette, 9:12 AM 5/31/2003]

Big Fish

My 2 cents: if the car overheats with a properly working thermostat it is going to overheat without one as well, and has other problems that need to be repaired. My own experience leads me to believe having a thermostat is the best way to maintain a constant operating temperature. Constantly changing temperatures has to be much harder on the engine. :cheers:

Pete79L82

It is not an old wives tale that removing a t-stat will make your engine overheat. The problem is that not all the information needed is included in that statement. On top tank radiators (Fords, some Chyslers, many GM prior to mid 60's) the radiator cap is on the same tank as the return hose from the engine. Without a t-stat or some restrictor the the water would return to the radiator with such force that it would open the pressure cap and push water out, thus causing the engine to overheat. That is where that wives tale started and people want to apply it to all situations. Our C-3 Corvettes have crossfolw radiators so the cap is on the feed side of the core so this is not a problem that applies to them.

The purpose of lt-1 reverse flow is not to make the engine run cooler, it is to make the engine more "even" tempatured. The cylinder head and the top 1" of the block are the hottest parts of an engine. By cooling them first, rather than the block, it creates a more even temperature insided the motor.

To achive maximum cooling you need to move the water as fast as possible. The longer it sets in the radiator getting cool the longer it is inside the motor getting hotter. The problem is you have to get the engine up to temp quickly. Nascar engines do NOT run a t-stat. But they are never started without the oil being preheated to at least 180°, and they use the electric fans to bring the motor up to temp quickly and they don't sit and idle at a stop sign. The engine is always up in revs to keep the water circulating.

The final conclusion is for best engine wear and drivability you need to run a t-stat on a street motor. On a race motor you should not run a t-stat but ONLY if you have a high volume water pump and are spinning it to at least 1-1 ratio.

Like big fish said "if the car overheats with a properly working thermostat it is going to overheat without one as well, and has other problems that need to be repaired."

bigvette1

Just a comment on the holes. I run the Stant Brand believe thier premium. I drill 2 1/8" or even use a 3/16" bit for holes across from each other. This is in addition to the bypass. This allows flow not only before opening but I have been told it will eliminate steam pockets that form in the system. The warmup process takes a slight bit longer but comes up to temp and holds a range between 185 - 205 on a bbc. Without the holes it runs hotter, I have tried both ways.

Red73

I've run without a thermostat for the last five years in my vette. I also use Evans NPG coolant that recommends you run your cooling system at little to no back pressure.
http://www.evanscooling.com/main21.htm

FNG

I have to agree with Rockn-roll. i have a griffen radiator with twin 11" spals in my 77. Bone stock except for dual exhaust and an edelbrock intake. It's not even summer here yet and my temps on the highway were around 210. then 215 Yesterday it went up to 220 on a little jaunt to Kyle canyon. It was morning and only about 90, nice day for a tops off ride. Stopped at a little store to get some goodies and i heard a slight "thump" that anyone who has ever had a frozen thermostat knows all too well. I have 4 1/8" holes in it otherwise i would have called a tow truck. as long as i kept it at low rpm it ran cool enough. This morning i took it out and went for another ride to the same place to test it out. Took roughly 4 block before the fans came on (185). Course we dont have a warm up problem here in vegas :jester , as it get quite warm enough this time of year anyway. Anyway....took it on the highway and ran it up to about 80. It's a pretty good hill on the way up and the temp guage started climbing. turned on the a/c to give it a good test, and let her rip. got to the high side of the 200 mark on the guage and stabilized rock solid right there. On the way back down, turned off the a/c. worthless anyway with the tops off and cruising at 70 plus. Car cooled down to about 190. Once back on the srteets i turned on the a/c again to see what it would do. never saw 200. Now granted it was morning and only about 90, but i have to think my problem was the thermostat. Did not run hotter with out it. Mush better flow. I did cut the center out of an old one to restrict flow somewhat, not knowledgable to know if that would make a difference or not, but RnR is right. iI probably will put another one in, but it will be when the stewart pump goes in. this summer it's staying out. Part was only a year old too. boiled the little sucker and it didnt open till the water was boiling rapidly and then didnt open all the way. oh well, my .02...........regards, fng

Rockn-Roll

Thermostats are made like a baby bird: cheap cheap cheap. Drilling holes isn't going to fix them. Ideally an electonic valve controlled by a temp sensor would be best. If there was something like that then I would use it as long as it opened all the way after the engine warmed up...without any of this partial open stuff, or closing down if the engine cools down below 195 or 180 or whatever the thermostat temp is designed to open at. Driving around with the possibility of the thermostat closing down is just plain scary...I'd rather try 55mph on a 25mph onramp before installing a $5 thermostat.


Yeah, from what I can tell the only way to use a thermostat with high performance engines is if a high flow water pump is used so that flows similar to that without a thermostat would be possible given that the cross-sectional area of the flow through thermostat will be less than without one. It will suck some horsepower from the rear wheels, but will help keep the engine from wearing faster due to the high heat.