Rebuilt Engine High Temp Issue

[geezer#99]

Originally Posted by garyd1961

This^has also been proven false.

By who!!

[garyd1961]

A 195 thermostat just makes sure the temp reaches 195 degrees before it opens and has nothing to do with cooling. If the water did stay in the radiator longer cooling it would also stay in the block longer heating. You need more water flow to cool not less. When I sit in front of a fan I turn it on high to cool me quicker not low. Why do you think they make high volume water pumps instead of low volume water pumps.
There is no magic here, it's all common sense. The more water flow and the more air flow, the more cooling.

[haysonj]

Originally Posted by geezer#99

By who!!

Google Temp vs wear in engines

[haysonj]

There is no magic here, it's all common sense. Yes the slower a liquid runs across a surface the more heat will be pulled out of it. This is why radiators have so much contact surface

[Stocker]

Good advice above. My two cents -- dump the flex fan for sure. Even if it doesn't explode, it will not cool well enough. Your shroud should accommodate an 18" fan; get a 7-blade if you can, or a more common 6-blade. Assuming the fan has 2 1/2" pitch (it should), get a heavy duty thermal fan clutch. Install without a spacer; the fan should be halfway inside the shroud, or as much as nearly all the way in. And if you don't have one already, get a coolant recovery tank and a cap for a sealed system.

In case you need more info on different types of fan clutches: http://www.haydenauto.com/featured%2...s/content.aspx

[71CHEVYSHORTBED402]

Originally Posted by cdowns

thermostats don't cool engines

IMO you're mostly right. They can stick closed and that's trouble. I believe the original thermo. was 190 degrees. I was told that was for emissions. The old man sold me a 180 for my 72 and everything seems great. Don't recall what's in my 71.

Back to Cdowns point, is your fan shroud correct? Also check your mixture. Should be about -37F, which is half water & half coolant.

[geezer#99]

Originally Posted by haysonj

There is no magic here, it's all common sense. Yes the slower a liquid runs across a surface the more heat will be pulled out of it. This is why radiators have so much contact surface

So does 'common sense' tell us that once the thermo opens, it stays open.
Does it ever close, even just a little bit?
Does the thermo impede flow at all?
Is there a pressure drop across the thermo?

[The Swed]

Yep clutch fan seems like the way to go... at what temp does the clutch fully engage?

[Stocker]

Originally Posted by The Swed

Yep clutch fan seems like the way to go... at what temp does the clutch fully engage?

Per the above link: "Engages at about 170° radiator air temperature, (about 30° lower than coolant temperature)." So about 200* coolant temp.

[GRX]

x3 (or whatever) on ditching the flex fan. Looks to be too far into the shroud too. Blades should be about a third way in to draw across widest area of rad as possible.

[garyd1961]

Originally Posted by haysonj

There is no magic here, it's all common sense. Yes the slower a liquid runs across a surface the more heat will be pulled out of it. This is why radiators have so much contact surface

You are just as wrong as you could be. If you run a qt a minute over a hot surface it will not cool as much as if you run a gal a minute over the same hot surface. Contact surface has nothing to do with the flow rate of the liquid. If you don't have enough flow your engine will over heat plain and simple. There is no such thing as over heating on account of too much flow.
To cool better you need more air through the radiator and more flow through the engine not less. Again why do you think they make high volume water pumps and not low volume water pumps?
People need to quit spewing such false info, just because you read it on the internet doesn't make it true.

To the OP get a good clutch fan, you will be surprised at how much more air it moves.

[Grumpy old man]

Pour some water wetter in it and watch the temp drop .

[davepl]

They didn't overheat when new. Run the factory parts and a 180 or 195 thermostat. That means get rid of the funky fan, get a stock one, with a good fan clutch, and make sure the fan is half-in/half-out of the shroud.

GaryD is right, the whole "slow the coolant down" thing is a myth, physics don't work that way. Or to sound like a beaker, "The thermodynamic transfer process operates at peak efficiency when the hottest coolant is exposed to the coldest air, which means keeping the coolant flowing as quickly as possible absent cavitation".

[garyd1961]

One thing I would like to add that a lot of people overlook is airflow. You need water flow but also you need good airflow through the radiator. Radiators get clogged with debris such as bugs, dirt and weeds and need to be cleaned sometimes. I'm talking about the air passages. I usually just run a light spray from a garden hose through the air passages once in a while. Don't use a pressure washer or you might damage the radiator, it doesn't take a lot of pressure.