BB Cooling Problem

[Tom B.]

Re: A simple experiment

Jerry,

I found your comment interesting. Can you shed any light on "Water Outlet Restrictor Kits" designed to reduce coolant flow from the engine block to improve cooling? I recieved that suggestion from another qualified individual and am usually open to ideas, especially if they are inexpensive. Any info would be helpful. Thanks in advance. Tom #24014

[Tom B.]

Re: A simple experiment

Jerry,

I found your comment interesting. Can you shed any light on "Water Outlet Restrictor Kits" designed to reduce coolant flow from the engine block to improve cooling? I recieved that suggestion from another qualified individual and am usually open to ideas, especially if they are inexpensive. Any info would be helpful. Thanks in advance. Tom #24014

[Jack H.]

Re: A simple experiment

Similar 'effects' can result from water pump rebuilds with different impellers as well as impellers that slip....

[Jack H.]

Re: A simple experiment

Similar 'effects' can result from water pump rebuilds with different impellers as well as impellers that slip....

[G B.]

Sharpshooters take aim...

Tom -

At the great risk of exposing just how much of the 1969 heat transfer course I remember, I will try to explain my opinion in more technical terms.

The radiator cooling system uses convection, conduction, and to a small degree, radiation, to get heat out of the water. The heat transfer equations have several variables, but the two biggest factors are the temperature differential (between the water and the air on the surface of the radiator metal) and the surface area (of the tubes/fins) available for heat transfer. For the conduction of the heat from the water to the metal of the radiator, the speed of the water as it passes through the radiator is not a factor. This transfer is (primarily) a function of the thermal conductivity of the water, the conductivity of the radiator metal, the temperature differential, and the surface area available. The water is only a means of convection for the heat to get from the engine to the radiator. In other words, the faster you can get the heat from the engine to the radiator, the hotter your radiator will be and the faster heat will leave the radiator into the surrounding air.

A restriction orifice in the water passage might provide backpressure to keep the centrifugal pump operating in the most mechanically efficient part of its curve, but the pump draws so little horsepower that we don't really care if it wastes most of it. We just want the pump to flow the highest volume possible.

I think some hot rodders have been taught that "cold" somehow soaks into the water while it is in the radiator, and the water has to stay there long enough for this to happen. In actuality, radiator retention time is not a factor.

[G B.]

Sharpshooters take aim...

Tom -

At the great risk of exposing just how much of the 1969 heat transfer course I remember, I will try to explain my opinion in more technical terms.

The radiator cooling system uses convection, conduction, and to a small degree, radiation, to get heat out of the water. The heat transfer equations have several variables, but the two biggest factors are the temperature differential (between the water and the air on the surface of the radiator metal) and the surface area (of the tubes/fins) available for heat transfer. For the conduction of the heat from the water to the metal of the radiator, the speed of the water as it passes through the radiator is not a factor. This transfer is (primarily) a function of the thermal conductivity of the water, the conductivity of the radiator metal, the temperature differential, and the surface area available. The water is only a means of convection for the heat to get from the engine to the radiator. In other words, the faster you can get the heat from the engine to the radiator, the hotter your radiator will be and the faster heat will leave the radiator into the surrounding air.

A restriction orifice in the water passage might provide backpressure to keep the centrifugal pump operating in the most mechanically efficient part of its curve, but the pump draws so little horsepower that we don't really care if it wastes most of it. We just want the pump to flow the highest volume possible.

I think some hot rodders have been taught that "cold" somehow soaks into the water while it is in the radiator, and the water has to stay there long enough for this to happen. In actuality, radiator retention time is not a factor.

[Louis C.]

Re: BB Cooling Problem

I checked the timing today and found 25 degrees at idle and 55 degrees total. Could this be a factor..............?

[Louis C.]

Re: BB Cooling Problem

I checked the timing today and found 25 degrees at idle and 55 degrees total. Could this be a factor..............?

[Tom B.]

I'll play the student......

Jerry,

I have great appreciation for your information. Your modest "opinion" appears to be more than that. Also, I have a note after the information.

The principles you describe are the exact function of a radiator. It also appears that radiators alone aren't capable of cooling the engine, which calls for the employment of clutch fans, foam seals, channels for air-flow, basically a "system" of components.

Obviously the more "distance" the coolant has to pass (through the radiator), the more surface area available for cooling. I can agree with the speed of the water not being a factor IF a radiator provides a sufficient amount of surface area (or distance) for cooling. If it doesn't, then it APPEARS that the coolant speed would be a factor, as the shorter the distance, the less surface area to provide cooling, and the result would be the "shoveling" of "hot" coolant back into the "furnace".

Jerry, my first admittance is the "lack of attention" to the principles involved, which I more than likely left behind in my textbooks. I was looking more for the "application" of those principles, hopefully with the experience others have had with this. I'm trying to find out if it's worth a darn or not, and from what you're telling me, it isn't. With more understanding I could end up agreeing with you.

Also, my note: I found your title to be a little unusual. Is there a boundary of inquiry that someone like me should be aware of not crossing? This hasn't been my profession, its my hobby. I post some responses, but I also ask questions and have plenty to learn. If I've been out of line, I apologize, and I can find my appropriate place.

Once again, thanks Jerry, and I appreciate your input with another one of the things I know little application about. Tom #24014

[Tom B.]

I'll play the student......

Jerry,

I have great appreciation for your information. Your modest "opinion" appears to be more than that. Also, I have a note after the information.

The principles you describe are the exact function of a radiator. It also appears that radiators alone aren't capable of cooling the engine, which calls for the employment of clutch fans, foam seals, channels for air-flow, basically a "system" of components.

Obviously the more "distance" the coolant has to pass (through the radiator), the more surface area available for cooling. I can agree with the speed of the water not being a factor IF a radiator provides a sufficient amount of surface area (or distance) for cooling. If it doesn't, then it APPEARS that the coolant speed would be a factor, as the shorter the distance, the less surface area to provide cooling, and the result would be the "shoveling" of "hot" coolant back into the "furnace".

Jerry, my first admittance is the "lack of attention" to the principles involved, which I more than likely left behind in my textbooks. I was looking more for the "application" of those principles, hopefully with the experience others have had with this. I'm trying to find out if it's worth a darn or not, and from what you're telling me, it isn't. With more understanding I could end up agreeing with you.

Also, my note: I found your title to be a little unusual. Is there a boundary of inquiry that someone like me should be aware of not crossing? This hasn't been my profession, its my hobby. I post some responses, but I also ask questions and have plenty to learn. If I've been out of line, I apologize, and I can find my appropriate place.

Once again, thanks Jerry, and I appreciate your input with another one of the things I know little application about. Tom #24014

[G B.]

Re: I'll play the student......

My title was just an attempt at humor. I really thought that other engineers in the NCRS (and there are many) would take some shots at all the stuff I left out of my answer. Your original request for more information was appropriate and extremely polite. The title of my post wasn't a response to your question.

The velocity of the water would become a small factor if the radiator tubes were much larger, say a foot in diameter each. At that size, the short time for the heat in the water at the center of the tube to travel to the inner skin of the tube wall could be measured. However, there in no significant time required for all the heat to get to the inner wall of a real world radiator tube.

You are correct about the other factors affecting cooling system performance. Certainly anything that increases the convection of heated air away from the tube surface will help cooling. This is the same effect as the "Wind Chill Factor" - increased convection cooling of a warm object normally cooled by conduction to still air. The use of radiator materials with higher thermal conductivity (such as aluminum) is another design idea used in many Corvettes to aid cooling.

Now I'll shut up so others can talk about boundary layer flow, the insulating effect of oxidation, the radiation potential of flat black paint over gloss black, and the many other factors I haven't mentioned.

Dilbert lives!

[G B.]

Re: I'll play the student......

My title was just an attempt at humor. I really thought that other engineers in the NCRS (and there are many) would take some shots at all the stuff I left out of my answer. Your original request for more information was appropriate and extremely polite. The title of my post wasn't a response to your question.

The velocity of the water would become a small factor if the radiator tubes were much larger, say a foot in diameter each. At that size, the short time for the heat in the water at the center of the tube to travel to the inner skin of the tube wall could be measured. However, there in no significant time required for all the heat to get to the inner wall of a real world radiator tube.

You are correct about the other factors affecting cooling system performance. Certainly anything that increases the convection of heated air away from the tube surface will help cooling. This is the same effect as the "Wind Chill Factor" - increased convection cooling of a warm object normally cooled by conduction to still air. The use of radiator materials with higher thermal conductivity (such as aluminum) is another design idea used in many Corvettes to aid cooling.

Now I'll shut up so others can talk about boundary layer flow, the insulating effect of oxidation, the radiation potential of flat black paint over gloss black, and the many other factors I haven't mentioned.

Dilbert lives!

[Tom B.]

Re: I'll play the student......

Jerry,

Thanks once again. Sorry about the confusion, it's a little hard to tell sometimes but I thought I was a "target" of stupidity (maybe I am!). Like I mentioned, more understanding on my part can help me agree with what you're saying. Since principles are involved with this, I'm still having difficultly getting past the "rate = distance / time" of the coolant. I'll keep pondering. Tom #24014

[Tom B.]

Re: I'll play the student......

Jerry,

Thanks once again. Sorry about the confusion, it's a little hard to tell sometimes but I thought I was a "target" of stupidity (maybe I am!). Like I mentioned, more understanding on my part can help me agree with what you're saying. Since principles are involved with this, I'm still having difficultly getting past the "rate = distance / time" of the coolant. I'll keep pondering. Tom #24014

[Louis C.]

Re: I'll play the student......

Tom & Jerry:

Thanks for the information, however, I feel like I got caught in a game of CAT & MOUSE! Humor guys! Yesterday I found that my timing was at 25 degrees at idle and 55 degrees total. Think this can be a contributor? I read an article in the Spring 1999 Restorer titled; "Summer Overheating." In the article (page 14) it explains that advancing the timing two degrees can reduce coolant temperature by five degrees. Retarding the timing will increase your coolant temperature. I called Tom Douglas and he said this is correct. I always thought it was the other was around!