thermostat, restrictor

[Dodge Freak]

My old Mopar ran half the summer and hit 6500 rpms most days and never leaked out if the cap or overheated with no T stat. Now I don't run the coolant right to the tip top of the rad but like 2 inches below since I have no catch bottle for the overflow.

[DCK]

Forgive my ignorance, but on my Dodge, there's that small bypass hose going from the front to the water pump. How does that affect things? I can't visualize it at the moment.

[Dodge Freak]

That is an outflow back to the pump, its for when the T Stat is closed the coolant can recirculate. I never blocked it off but hear good and bad from those who tried, some saying it was fine-others saying the motor ran hotter.

The Edelbrock Victor pump has those fittings threaded so it be easy to plug, the other opening is for the header hose, the intake flow...all coolant outputs are on the intake front runner, all coolant inputs are on the pump. That is for the SB Mopars, pre magnum not sure if the later motors are the same.

[77cruiser]

This is where the old wives tale of “the water goes through the radiator too fast to cool” comes from. Remember, if it’s too fast through the radiator to cool, it’s too fast through the block to get hot, opposite sides of the same coin so to say.

Then maybe the water is going thru the block to fast to cool the block

What do you think would cool something down quicker? Pissing on it or using a fire hose?

[jpankey]

the firehouse will but thats totally different. thats like having a engine screaming hot and sticking the water hose in it without the engine running cools so quick it cracks stuff. when dealing with heat exchangers which is what a radiator is fluid to air instead of fluid to fluid they are a temperature thats measureable its known as approach and its simply the heat that didnt get transferred for various reasons to much gpm to much velocity or just simple fouling due to corrosion. the water simply has to have sufficient time in contact with the surface you want to absorb heat from and sufficeint time in contact with the surface you want the fluid to reject its heat through such as the radiator to achieve proper heat transfer.

[Troy Patterson]

There is truth to running the coolant thru the cooling system too fast - when not running a thermostat or restrictor. I'd say it was application dependent though.

I've seen engines with no thermostat running cool enough with little or no load, then go hot as soon as there is any real load put on it - without ever losing any coolant out the cap.

If the cooling system is killer for the application, then there isn't likely going to be a problem.

Something more to consider however is that the engine will take longer to warm up without a thermostat and it may cool undesirably / excessively when not under heavy load, not generating lots of heat - changing internal tolerances. Either the engine is intended to run hot / warm or cold, you can't have it optimal for all. Pick one and design your cooling system to maintain that temperature under all conditions for best engine life and performance / power output.

There is an issue with passing coolant thru the head and block to quickly. After all, few take the time to engineer or port the cooling system to maximize efficiency and prevent cavitation thereby reducing heat transfer in those areas creating hot spots - which is does puke coolant out the radiator cap / overflow.

The more pressure your cooling system can handle, the better the heat transfer as the vaporization of coolant develops more slowly and is replenished or moved down stream more quickly.

Does running more pressure in the cooling system mean you can pass coolant more quickly through the cooling system? Not necessarily. This is a separate issue dependent on cooling passages in the block and heads.

Troy Patterson TMPCarbs.net TMP Carbs

[340king]

I run a dirt modified on gas. It is a metric frame car, so there is very little room for a radiator. I run without a T-Stat or restrictor. Engine runs about 210° under racing conditions. Haven't had any issues with the setup. This is on a SBM. So you can chalk me up for one on the "it works" side.

For the record, I ran a thermostat prior to this. It wanted to run warmer with the T-stat than without. I run with the bypass hose removed and the ports plugged. I drilled a 3/16" hole in the T-stat plate to allow some water movement prior to opening. I had no issues with that part either.

I run the water pump at about a 15% under drive with a smaller crank pulley.

I am a mechanical engineer and agree with the nuclear power plant designer. Using the too fast analogy, then why don't radiators fail to cool as speed increases. Wouldn't the air be moving "too fast to cool" as it passed through the radiator????

[Dodge Freak]

I been drilling a few small bypass holes in every T Stat I install, even my old mans new Buick motor got a 180 T Stat with a small bypass hole drilled in it the first week he got it. Funny the temp gauge reads the same as when a 195 was in there, I check the parts books and either T Stat is OK for those 3.8 motors. Does it help / don't know but can't hurt I feel.

[LJW]

Have you ever stood outside in the winter and had the wind blow by so fast you didn't get cold?

[Tuner]

Have you ever stood outside in the winter and had the wind blow by so fast you didn't get cold?

Right on.

[77cruiser]

Have you ever stood outside in the winter and had the wind blow by so fast you didn't get cold?

Have to remember that one!

[SWB]

There is an issue with passing coolant thru the head and block to quickly. After all, few take the time to engineer or port the cooling system to maximize efficiency and prevent cavitation thereby reducing heat transfer in those areas creating hot spots - which is does puke coolant out the radiator cap / overflow.

There is a point here.

I've seen some cup engines with all kinds of attention to detail in this area. Water flow is just like air flow but less compressible, so the same basic rules apply. Where the flow restrictions occur will have a significant impact on how the water flows and thus the localized pressures as well. Since pressure is directly proportional to the boiling point (and thus the coolant's ability to cool), this is something to think about.

[Lazy JW]

Have you ever stood outside in the winter and had the wind blow by so fast you didn't get cold?

It's my understanding that the SR-71 went fast enough that the air friction actually heated the airplane to the point that it caused a major design issue(s).

Thus far, every time I have removed a thermostat, the engine has ran cooler. Maybe I'm just lucky, eh?
Joe

[1989TransAm]

Milodon makes a high flow thermostat. I will be using one on my next engine(motor) so I have no experience with them yet.

[DCK]

Have you ever stood outside in the winter and had the wind blow by so fast you didn't get cold?

It's my understanding that the SR-71 went fast enough that the air friction actually heated the airplane to the point that it caused a major design issue(s).

Thus far, every time I have removed a thermostat, the engine has ran cooler. Maybe I'm just lucky, eh?
Joe

From some Air Force buds from when I was in, the SR-71 would leak everywhere on the ground, but when it got up in the air and up to speed it would stop. The heat helped all the panels expand and seal up. I believe that it had to be designed that way in anticipation of the heat from air friction. The plane would actually get a little longer also from the heat.