Is there some compelling reason not to use a thermostat ?

 

I dont know thats why i ask. Ive seen circumstances where people cant seem to get one that doesnt stick, or deleting the heater or having high compression motors, dirt track cars getting radiators plugged from dirt. Ive had plenty of thermostats that didnt open.
But doesnt the thermostat restrict the flow of coolant so it has sufficient time to cool down? Just seeing what people thought about washers taking place of a tstat

 

The thermostat manages flow rate to establish a constant operating temperature. If it cannot do that then something in the function, design, and operation of the cooling system is not correct. This is assuming the thermostat does not incurr a failure which is pretty rare.

Flow restrictors are used in competition engines to sort of achieve the same end without the possibility of having a thermostat failure out on the track. 60 years of racing has shown me this fear is far more fantasy than reality, I think I've only seen 2 maybe 3 thermostat failures in all that time and two of the three stuck open and even at racing engine loading the damn things ran cold, but they kept running.

The problem with sustained high speed high RPM runnng usually is too much coolant flow, so the restrictor is used to reduce flow to maintain some averaged range of operating temperature which of course to discover you have to put some size resrictor in, then go out on the course for a bunch of hot laps to see what temp's you get. So you're going to be at this awhile.

Bogie

 

Isnt it true that the oils we use work best at optimum temps say around 190-200?

 

Ive been using them for years. I actually use a large 1" flatwasher...thin as can be found. Works excellent....temps right at 185-200 max...full tilt small block

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I use restrictors. No problems.We used to drill holes in the perimeter of a thermostat for better flow rates. Like BogiesAnnex1 states thermostats are quite reliable now

 

How consistent are the temps? Outside temps a factor? Im just curious, i just saw them offered by moroso in a classic industries catalog and wanted some insight of these things

 

For what purpose?

A restrictor on the street in the southwest or deep south east weather isn't a big deal. If you live where it gets cold you'll have to do a hell of a lot of driving to get the engine up to temp if that can even be done. Drilling three 1/8 holes in my daily driver's thermostat to help with burping the system in various experiments required frequent drains and refills so to speed that up the holes were put into the thermostat. These changed the warm up on the coolat gauge from 1 to 6 miles in Puget Sound's pretty chilly but not bone freezing winter weather. That's just coolant, it delayed getting the engine oil up to 180-200 degrees for another 6 miles at interstate speeds but since I put at least 60 miles into each side the commute this wasn't a problem as the engine finally got the coolant and oil up to temp fora goog period of timee. So if this is a street mobile your just asking for troubles you don't need without a thermostat. Now that my machine and I have transitioned to retirement, I put a high flow thermostat in it with no bypass holes. In winter on long freeway runs the gauge reads 4 degrees under the thermostat opening temperature of 180. It gets there quickly in about a mile to mile and a half from a cold start which includes a minute of fast idle before dropping it in gear to warm up the unheated intake a little. Anote on a related subject, I had more intake icing issues with the 670 cfm GM TBI and aluminum manifold adapter than I've had this winter with an AVS with insulating adapter to the same manifold.

If you're have cooling problems you need to identify the root cause and fix them rather than install what appears to be a crutch.

If you're racing then you'll have to pick a size and try it out, generally 7/8 ths to 1 inch is a good starting point. The operating temperature will vary with load on the engine and weather as the cooling system except for engine RPM is operating in a static flow condition so operating temperature will vary with the conditions where a thermostat will vary its opening thus coolant flow to reflect these changing conditions, at least within its range of authority. Like I said earlier if it doesn't do that the system, which can include the thermostat, has problems that need to be identified and fixed.

Bogie

 

restrictors are for race cars. on the street use a thermostat.
for oval racing I use a 1 inch hole restrictor for typical 5-600hp compression engine

 

I'm just gonna leave this here because it covers it all.
In fact, following all of these tip eliminates much misconception.

https://www.stewartcomponents.com/index.php?route=information/information&information_id=11

 

restrictors are for building pressure in the block, not controlling flow rate

 

NO, they are not......the cooling system being closed will build pressure from heat....the pressure is uniform throughout the cooling system.

 

Wrong...restrictor reduces flow. A 1" restrictor slows it ever so slightly to allow heat removal, and enough flow for high RPM runs. If you have a low HP daily driver that never or hardly ever sees above 5k RPM then use a thermostat. My RPM at highway speed is around 3300-3500 so I ensure enough flow available through the block especially with reduced ratio pulleys....no matter what Stewart says, it has been done with success for 50 years. And i use one of their no-bypass high flow pumps

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Now im thinking, you say low HP daily driver what is low hp. Also, how about say a 350 bored .60 over where the cylinder walls are thin therefore more heat produced in the water jacket? Guess its more or less personal preference as to run thermostats or restrictors. I personally have never run a restrictor. I have an older monte carlo with a 350 i could do some "experimental testing" on......i dont really care if it over heats as its sits waiting for a facelift

 

I hate when this happens......Johnsongrass1 posted a VERY GOOD LINK about cooling systems......

YOU CANNOT FLOW TOO FAST IN A COOLING SYSTEM! The old adage about keeping it in the radiator longer is the biggest myth ever perpetrated on the automotive industry next to storing batteries on a concrete floor!!!

I wish people would stop saying you need to do that!!!! The best setup is with no t-stat at all and a high flow water pump! T-stats are used to maintain a certain temp and are the result of emissions controls!! An engineer for NASCAR frequents Speedtalk and goes by the nickname of Warp Speed. He works for Hendrick motorsports....Ask him if they use a t-stat or restrictor in their engines....

If you need a heater to work, you need a t-stat, but a t-stat will INHIBIT cooling. That's why the engine temp will climb with one. When it opens it will allow more cooling to take place, then close down when the temp drops....a restrictor does the same job for a short time until the water temps have stabilized, then they are useless...

 

Quite right, more flow is good, unless you get so much that the pump cavitates (never seen that). I don't run a thermostat in my T-bucket, but use electric fans with a Jeg's fan control unit that varies fan speed to maintain a set temp. This is of course a street rod; I imagine racing is a different deal.

 

I really dont think I'll ever refer my 66 impala to a nascar, which will never get rebuilt after a 500 mile jaunt.they dont sit in traffic either. This summer ill take that monte i have and do some testing for my own eyes, in my type of conditions to see how different the cooling characteristics are with a thermostat, with a high flow stat, no stat and different size restrictors. I know it wont be a controlled test as i wont have the exact conditions every time i change something.ill be doing this as People say yes and people say no about tstat or resistrictor or none, and these people have been around engines WAY longer than i have! Kinda wanna see for myself how much it makes a difference with my type of driving habits and my type of weather conditions! Great input guys!

 

A water pump works on a paddle wheel effect. Water is taken from the inlet of the pump and quite literally flung to the outlet side. Why do you think the impellers are angled? The pressure comes from heat buildup and a water pump will circulate water with or without pressure of any kind in the cooling system. The pressure in the system is fairly uniform throughout, as it's a confined system. There are some minor differences in pressure in some parts of the system but that is due to whatever restriction to flow there may be. I'll say it again: a water pump does not need pressure to move the water in a cooling system. If that were the case it would move zero water until pressure builds up which is not the case.

 

I would test it.
With a good pump, proper drive speed, on a dead cold engine, the pump should produce about 30 PSI in the block.

 

Pumps do not produce pressure....only flow........

 

Pressure is resistance to flow , without pressure , there is no flow and vice-versa......its semantics( or theoretical engineering gobbledeegook) LOL. Or artificial contention creation !!...

 

You're correct on pressure, pressure is created by resistance to flow. However, you can have flow without pressure, and have pressure without flow....

For the flow without pressure, all that's required is a pump to move the fluid through a conductor such as a hose. If there is no restrictions in the hose, you'll get flow from the pump but no pressure.

If you take the same thing and plug the end of the hose, while keeping the pump working, you'll build pressure behind the blockage, but flow will stop.....

Pressure will build until one of these things happens:
Flow is stopped.
the pressure is relieved through the use of a regulator (it will build to it's set point then level off)
Something fails in the system.......

Basic hydraulics....a cooling system is no different, they both work the same....

 

As for the pressure in our cooling systems, there is very little resistance in flow through the system, even with a t stat. Systems equipped with a t stat have a bypass to allow water to recirculate to the inlet side of the pump. Without it, the pump will cavitate. Most t stats have a small bypass hole built into them to help with this as well. If the t stat isn't open, the water will simply recirculate until it does....So the restriction to flow in the system is fairly constant with little change. The majority of the pressure buildup in the system is due to heat and expansion of the coolant AND the air in the system. Like it or not, our cooling systems have some air in them. As the coolant heats up, it expands slightly. This works against the physical restraints of the system, and as a result, creates pressure. The small amount of air in the system does the same. It will build until the cap relieves the excess, whatever it's designed for pressure wise. It will open and close to maintain that set pressure. Once the system cools down, the pressure will drop. However, it needs to cool beyond a certain point for the pressure to completely dissipate, and generally unless you live in a very cold environment, you'll always see some static pressure remain in the system.

 

One more thing on pressure in our cooling systems. They are a closed system. Once pressure builds, it is uniform throughout the system, take a look at Pascal's Law here.....at that point, if there is a restrictor in the system, it WILL NOT affect pressure....only flow.....it will slow it down. The pressure will be equal on both sides of the restriction however.

The water pumps we use are NOT a positive displacement pump. There is considerable slippage inside the pump when it's trying to move water. That slippage creates cavitation, which is why it's allowed to bypass the t stat and recirculate. This limits that from happening, although it still does to a point.

 

Yada Yada Yada feel better now , where's the whip to beat the horse ??LOL

 

from the link to Stewart pumps provided:
"Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine."

Pumps seem to produce at least some pressure, and not just flow.

 

No, they don't. Unless you've discovered a way to change physics, it ain't happening. What was happening is the low relief setting on the caps didn't allow for the temperature rise and as a result the water would begin to boil. (Raising the pressure water is under also raises the boiling point). The excess pressure created from the water boiling caused it to push out. This problem was solved by using higher pressure rated caps and adding ethylene glycol. The combo of the two raised the boiling point and solved the issue. It will still happen now if there is insufficient cooling. We provide an overflow tank to catch it now and a cap designed to allow the water to re-enter the radiator as it cools. This is what is more commonly known as OVERHEATING.

I'll say it one more time, pumps do not nor can they create pressure. They can only create flow.