[RR67GTO]

Greetings, in this months issue of HPP magazine in the wrenching section questions and answers there is a detailed answer about engine temperature. The response is from Rocky Rotella, and I found it interesting. I just wanted to pass it along since I found it informative. Best wishes friends. Mike

[getmygoat]

I was surprised he was espousing the idea that coolant moving too quickly does not have time to give up its heat in the radiator. Therefore, he claims coolant should move slowly to cool best. That seems incorrect.

I believe this discussion has been on here in the past, but a fluid moving fast through the radiator is also moving faster through the block/heads, therefore each cycle around may transfer less heat per water molecule, but each water molecule is making many more cycles because it is moving faster.

If you imagine water moving through the system at lets say, the speed of light, the temperature of the water would never go up, because any heat picked up through the block would be immediately released in the radiator.

I suppose its possible that if the water pump is too strong, it creates vortexes and other destructive phenomena with the water flow... if this was the case, any lack of cooling wouldn't be due to the water moving too fast through the radiator. - Also - I assume the drag of the coolant passages in the radiator tends to maximize the speed at which water moves through it... Also, since the pump is sucking from the bottom of the radiator, the ability to suck the water through those fins is likely inhibited.

For what its worth, this article seems to confirm my analysis and contradict Rocky's
http://www.carcraft.com/howto/ccrp_0...m/viewall.html

[Pontirag]

I read it, My opinion differs from his on certain points. Not sure what his sources are. I am fortunate that I learned all I needed to know about cooling systems befor the internet existed.

[Rocky Rotella]

Guys, just to clarify some points on this, a few years back, I was having some cooling issues with one of our engines and spent a great deal of time discussing my issue with coolant system specialists. One was a major radiator manufacturer.

It was confirmed that if coolant passes through the radiator too quickly, whether due to pulley ratio, impeller volume, overall radiator volume (say, too small for given application), or any combination of above, the coolant may not have ample time to exchange heat. It basically returns to the engine at a warmer temperature than with a radiator that cools more efficiently. Aluminum is common today because it lightweight and more efficiently dissipates heat and the aftermarket radiators are rather large, so we don't often consider it an issue, but Pontiac used many different radiators in its original applications. If coolant capacity and how much time the coolant spent in the radiator wasn't important, Pontiac would have used only one size.

This particular reader notes a high-flow water pump (source unknown so quality and/or volume is any one's guess) and an aluminum radiator. I never suggested he needs to slow his coolant system down. I simply said I wouldn't expect to see cooling issues occurring with an aluminum radiator. Knowing how well an aluminum radiator can work, I suggested he verify the gauge's accuracy.

[Pontirag]

and other reputable sources claim that pumping coolant through twice as often exchanges heat twice as often

And an article in hemmings Mucle car magazine a few years back in an article about aluminium radiators a vendor interviewd stated that aluminum radiator advntages was weight and not heat disapation.

so

Its not that you or anybody else are wrong at all its just that there is conflicting information , advertising claims and myths

[GT182]

Rocky, then in a nutshell, would you say the waterpump pulley size is also a factor. I never had any of the 3 I owned back in the early 70s overheat on me.... 66 GTO, 63 GP, 66 Tempest. Not even the 79 301 Formula I drove for almost 12 years.

For the life of me I cannot understand why a stock 389 or 400 back in the day wouldn't overheat. But these days everyone is having some type of overheating problem with a stock engine. I wouldn't think the difference from a 190°/195°(stock from the factory) to a 180° thermostat would be in the mix.

[RR67GTO]

Since I started this post I wanted to mention what I found the most interesting about the article. It was the fact that maybe we are to worried about the temperature readings we see. I understand we spend a lot of time and money, building our engines and want to protect them. But from what I read, 200 degrees is nothing to worry about. What I experience on my car is that once the temp reaches 200, it seems to lose low end power. Of course I understand the basic reasons behind this, but it seems to be more pronounced than what I remember. Mike

[george kujanski]

A while back, i looked at some mfgr specs for a welded plate heat exchanger. The graphs clearly showed that the heat transfer increased as the airflow OR coolant flow increased. I tend to agree. An automotive radiator technically is no different.

George

[Don 79 TA]

i can kindda vouch for the moving too fast thru the radiator
perfect examples are the MJ/XJ jeeps
some think just swapping to a lower 160 stat would aid in cooling, when essentially it hurt it, mainly because these models use a very small radiator. using a higher temp stat helped keep the cooling inline and more stable, stayed in the radiator to cool versus just fast flowing thru
it's a pretty well known issue on those models
may or may not apply to something old like the pontiacs, because of their larger radiators

now my cooling experience with the pontiac:
when i went with under drive pulleys i noticed the temps were higher compared to before
a 4 core radiator helped vs the 3 core
a flow cooler water pumped helped as well, almost back to the point of where it was in stock form
electric fans... well i've always just had positive results from them (like no more splicing hands on the flex fan)
electric water pump... outside the price tag... positive results, ok.. the negative is the weight of the sucker and it actually cools maybe a little to well at low speeds

[gmot455]

I agree. The coolant can run too fast through the system to cool it sufficiently. Try putting a 455 engine in an older 64-66 GTO. I tried 3 or 4 different radiators. Ones that say 'will cool 650 HP' . I tried 2 1 inch cores, I tried 3 cores with electric fans and shrouds. I tried high flow water pumps. Nothing would keep the STOCK 455 cool in traffic. You have limited selection with the small amount of space in the early cars. Then I FINALLY found a 4 core aluminum radiator that would fit the space. It was not designed for Pontiacs, but for some old Chevy truck. The cap was in the middle, and didn't fit the fan protector plate holes, but that radiator lowered my temp by twenty degrees. I didn't even need to turn the electric fans on anymore except on real hot days. So, a 455 needs a 4 core radiator, period. I just picked up a 1974 GTO with all brand new parts, and guess what. The brand new 3 core steel radiator will NOT cool the 455 in the car, so here I go again, trying to find a 4 core radiator for a 1974 GTO, that will fit in the radiator support. Maybe I can find one for a Nova that will fit.

[george kujanski]

So what does the 4 core have to do with the flow rate? In fact the flow rate is probably faster due to the lower restriction in the 4 core.

Instead of a steel radiator, i think you mean brass/copper. Don`t know of a steel radiator used in cars.

Just sayin`.

George

[george kujanski]

here's yet another graph of heat flow vs. air and coolant flow.

Here's the link to the full article: these folks were designing a smaller radiator to match the performance of a given unit.

http://www.maplesoft.com/view.aspx?S...tor.pdf‎

physics is not subjective.

George

[Jonsey]

Another way to think of it, since the cooling system is a closed loop, the water spends the same total amount of time in the radiator no matter how fast it circulates.

[geeteeohguy]

The A/C equipped Pontiacs have a smaller water pump pulley to drive the water pump faster and pump more water at any given rpm. AC equipped cars generate more heat than non-AC equipped cars due to the restriction (and heat) of the condensor in front of the radiator. To me, this means a bit more is better to keep things cool.

[68 Firebird]

Agreed with gto guy. I noticed a difference in cooling when I swapped to
a smaller WP pulley. Remember both the water pump and fan spin faster that
that way!!

Gerry

[Region Warrior]

Larger core flows more air and water.
Smaller w/p pulley increases speed.
We all know that.
A/C and HD cars used larger 4 tube radiators. More water/larger core stands to reason it takes longer to travel through.

Other stuff.

State of tune on engine a no brainer.

Is there any air space between radiator and core support?
Air can be sucked through there.

Large openings on top/front of core support?
Can air be recirculated back over from engine compartment at idle.

Fan shroud no brainer.
But is fan located correctly?
To far in not so bad, to far not good.

Auto trans cooled in radiator or have an auxiliary?
Trans fluid obviously adds heat.

Is the engine rpm ideal "power range" at cruise vs rear gear ratio?
Lugging below it or over it makes engine work harder creating more heat.

Stock torque convertor?
Higher stall creates more heat.

Point is the entire system has to work together.
There is no right or wrong as long as it functions well.
My 68 FB has a 4 core radiator w/shroud and 19-7/8 flex fan(clutch type works same, just don't like all that weight on w/p bearings).
Large non A/C pulleys.
Auxiliary trans cooler.
3500 stall cnvtr with 3.42's
Nothing else. No front baffles or covers.
Drive all day long during summer, go round robin at track in 90 plus heat 11.80-12.00 @ 114 mph. Never gets to 190 w/a 170 stat.
Or get to 200 w/a 180 stat.
1st 68FB had 3.73s, ran same temps.