[studda]

If the hood was closed, the top end of the motor would probably be black, while the bottom end would be whatever color the motor was painted. If there is no light, it is black like the example of space. How much heat though is transferred through non-direct sunlight? Wouldn't it have to do with the color of your hood and fenders absorbing heat as well(heating, or slowing the cooling of engine compartment down)?

[Mike S]

Ok since we must be bored, someone with a laser temp probe do an experiment. Get a white paper and a black paper set them on a table and let sit to get to room temp out of sunlight. Or better yet on a heat source. Wich one is hotter? If black radiates heat better would the black paper be cooler? personally I think it's a bunch of bull. Paint only reflects or absorbs. If this was true every engine would be black. Heat ALWAYS transfers from hot to cold. Everything has some form of heat. The absence of heat is cold.
Mike S

[studda]

The absense of heat is cold and that makes me think. If a black and white object of the same material was at absolute zero(-478 degrees F), which would heat faster? Same material, same rate. They would both have the same heat capacity and therefore use the same energy to retain heat and would actually cool slightly by using this energy. But the black paint may have a higher or lower heat capacity depending on what is in it that makes it black as opposed to white. I would say that it really depends on the contents of the paints used.

[screamingchief]

The black piece of paper will be hotter because it's absorbing more energy than it's able to shed,but does that not also mean that the energy source released more of it's own energy via the black sheet of paper?

Will it not also heat the area surrounding the black piece of paper more-so via it's attempt to shed its own heat?

The more it absorbs the more it will have to attempt to shed...

[pontorquer]

GOOD GUYS WEAR "BLACK" SO DOES GOOD PONTIAC ENTHUSIASTS !!!

[george kujanski]

Studda: in your previous post you say black is the absence of light...I say no, the absence of light (visible) is dark.

Black is a color which reflects very little of the visible spectrum of light to your eye.

If the underhood is sealed so no ambient light gets in, the engine does not turn black; it doesn't change color. The underhood becomes dark; i.e. there is no (visible) light. Now IF your eyes were sensitive to infra-red, in the above scenario you would "see" the infra-red coming from the warm engine, and the parts with higher emissivity would "look" hotter (or brighter).

George

[gearbanger]

George, that is correct as I learned in Physics. Therefore I do not believe this theory. I believe the black would cause hotter running temperatures if anything.

I have also heard that painting a radiator makes it not disipate heat as well. So I would guess that not painting an engine, as alot of engines are these days, would be the way to make it run the coolest.

I would be willing to bet money that you will not see a 20deg difference either way, no matter what color you paint it, or whether or not you paint it at all.

[studda]

All that is in a color is the pigments that reflect certain wavelengths of light. If there was no light, there would be no wavelengths to reflect. But yes, the pigments are still there.

[studda]

I agree with your no paint idea. It would be like wrapping the engine in a cloth. No matter what color the cloth is, it will have some insulating properties and hold heat as a result.

[george kujanski]

I tend to agree that a layer of paint of any kind may actually reduce heat CONDUCTION from the engine metal to the surroundings, i.e. air, but the emissivity, which determines the RADIATION of heat (a separate machanism) depends on the material characteristics such as color, texture, etc. as can be seen in the referenced table.

George

[screamingchief]

it will have some insulating properties and hold heat as a result.

Where is it taking that heat to hold from?

It certainly is'nt creating it on it's own...



Like I said before this is all HARDCORE theory,it could be discussed for/against for a good long time and no concensus would be reached here regardless.

Like George points out there is more than one type of dynamic at work here,and the materials involved,and their properties will greatly influence this all as well,as will many other things,thats why I said I dont hold much to this,its too dificult to quantify in the real world with the practices were forced to adhere to.

[Speargun]

In the visible light spectrum, light colors reflect and dark colors absorb the energy.

Radiant energy works a bit different and would take a Phd to explain it all, but ask yourself this simple question;
Why is the bottom of the space shuttle black?

[wheelspin]

This thread is beginning to look like perpetual motion, kind like the discussions about the 7-10hp differences between intake manifolds such as the HSD, Tomahawk, and RPM . Seems to happens every time race season is over .

Les

[firebirdcrazy1959]

i painted mine black because i liked it

[BLACK SUNSHINE]

Originally posted by pontorquer:
GOOD GUYS WEAR "BLACK" SO DOES GOOD PONTIAC ENTHUSIASTS !!!

Thats right baby!!! Go White Sox!!! World Series Champs

[BVR421]

Feel the HEAT!

[SupergasDil]

The fact is that Pontiac blue makes more power!

[Bud Lyons]

We should call Myth Busters. They can solve anything in a 1 hour show.

[Ron Landis]

Originally Posted by BILL BOWMAN1

Agreed, cuts time, waste, manhours, supplies... More money in company's pocket with one color.

why not just do like Ford, and don't paint 'em at all?

[bobzdar]

I would submit an un-painted engine would dissipate the most heat as it's one less layer of insulation on it. However, it'd corrode, especially if aluminum. Color doesn't really matter when it comes to heat, it's infrared radiation, not visible radiaton you need to worry about. Besides that, most engine heat is conducted out through coolant, not radiated from the block. Most electrical heatsinks that have to do a really good job aren't painted at all, the paint layer would insulate against heat being transferred from the component to the heatsink and again insulate it from radiating out of the heatsink. The only time they'd be painted is when made larger than needed so any loss in efficiency would be more than made up for by corrosion resistance if needed. Look at any of the higher level passive cooling solutions for computer cpu's and video cards, almost all are unpainted. The only thing on them is thermally conductive paste to fill in any gaps on the surface of the IC and heatsink (any air gaps will insulate) and nothing on the exposed areas.