I recall reading about this before. Radiators painted black, NASCAR engines, other instances as well.
What do you people think?
What do you people think?
Any truth to the practice of BLACK painted parts dissipating heat better?
- Thread starter Kern Dog
- Start date
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A black shirt is hotter in the sun than a white one. But according to those who say black dissipates heat, a black engine on a stand should run cooler, even in the sun, than a blue or orange one. Makes zero sense to me.
Black absorbs heat? That I agree with. Hence the black shirt.
Black absorbs heat? That I agree with. Hence the black shirt.
mopowers
Well-Known Member
Isn't anything black if it's under a closed hood not exposed to light?
I'm not convinced of or doubting this theory. I just am looking for some rational explanation.
spycam
Well-Known Member
As an old physicist I recall that black is the best at dissipating (radiating) infrared which is what the engine produces (see Black Body radiation). The best absorber is also the best radiator.
mopowers
Well-Known Member
I remember hearing this idea too and always wondered if there's any truth to it. I would think the added insulation from the additional layer of paint would negate any benefit (if there even is any) from the particular color a radiator may be painted. That's just my dumb theory though.
spycam
Well-Known Member
Phreakish
Well-Known Member
It may be true, but the difference would be minimal. Convection is going to remove far more waste heat than radiant losses, by orders of magnitude.
Radiant heat losses increase as a function of temperature differential, and so significant heat shedding won't take place until we'll beyond the operating limits of many engine designs. That's why every engine I can think of employs convective cooling via water or forced air.
It's also worth noting that radiant heat exchange would require any heat shed from the engine to be absorbed by an adjacent or nearby material, typically in direct line of sight. The heat then would need to be pulled from that panel or part in order to continue absorbing heat from the engine..
In other words: a proper mix of coolant will do more for you than a black can of krylon.
Radiant heat losses increase as a function of temperature differential, and so significant heat shedding won't take place until we'll beyond the operating limits of many engine designs. That's why every engine I can think of employs convective cooling via water or forced air.
It's also worth noting that radiant heat exchange would require any heat shed from the engine to be absorbed by an adjacent or nearby material, typically in direct line of sight. The heat then would need to be pulled from that panel or part in order to continue absorbing heat from the engine..
In other words: a proper mix of coolant will do more for you than a black can of krylon.
spycam
Well-Known Member
You thinking of going all Chebby and painting your engine bay black?
There is one thing I can tell ya. Very hard to find an oil leak on a shiney black engine.
Heck no!You thinking of going all Chebby and painting your engine bay black?
I have a 318 here that was painted black and I have to replace the heads. I told the owner that black makes it harder to spot leaks. It got me thinking about the stories about heat dissipation.
Maybe all manufactures starting painting them black including Mopar is that black paint is half the cost of a color.
ragtopfury
Well-Known Member
I can debunk this myth with 2 flavors.... Chocolate ice cream melts faster than vanilla.
Not only that, but this......Helped Josh with a 5th grade science fair project 3 years ago. The theme was do light or dark colors get hotter. We painted 4 aluminum panels. White, yellow, green and black. The black one was always warmer in all settings. In the sun, in the shade, under a halogen flood light and even just lying on the garage floor.
Also, sitting in the sun, my buddy's dark blue Ram was always hotter inside than my white Ram.
Not only that, but this......Helped Josh with a 5th grade science fair project 3 years ago. The theme was do light or dark colors get hotter. We painted 4 aluminum panels. White, yellow, green and black. The black one was always warmer in all settings. In the sun, in the shade, under a halogen flood light and even just lying on the garage floor.
Also, sitting in the sun, my buddy's dark blue Ram was always hotter inside than my white Ram.
Right! Not disagreeing or trying to dissuade anyone of their theories, but can anyone explain this; Try painting your foam core front door on your house facing south white or black.... the white will reflect the light and stay cool, the black with absorb heat and literally melt the foam and the glue will run right out of it, especially if you are in a warmer climate!! So, black can only dissipate heat in the dark???
/confoosed in Ohio lol
Not being a wise azz but dark skinned people are from hot climates (africa, middle east). Not because of the sun but skin pigment. Natures/GODs way of keeping a body cooler through heat dissipation?? Food for thought.
I remember an article in Hot Rod or Car Craft magazine years ago on this. If I remember correctly, they painted a SBC black and checked under hood temperatures and it seemed to be cooler.
And that's why I'm doing my engine bay and engine in white. Same as an aircraft landing gear bay. (Heads and valve covers red and white stripes, water pump, timing chain chain cover and air cleaner get blue, and white stars on the air cleaner. veneath the leaky areas though it's white. I still haven't decided on the intake manifold color, probably a clear over bead blasted aluminum)
I'm pretty sure that's different. The melanin blocks UV light, which causes injuries. It also blocks the light needed to synthesize vitamin D, and with much less light in the higher latitudes in winter and consequently less vitamin D deficiency, prior to mechanized travel and vitamins people DIED or became more susceptible to disease because of vitamin D deficiency. Evolutionary pressures killed those with more inherent resistance to skin damage from sunlight, as well as selecting for REDHEADS!
So, Merry Christmas!
There are some people do that.You thinking of going all Chebby and painting your engine bay black?
First picture is how I bought the car .
Second picture is after I put another motor in.
Third picture os after looking at it I just couldn't let that engine compartment like that so I repainted it.
Black has its place at times but not under the hood of classic a mopar muscle car.
Mopar44134
Well-Known Member
This is my understanding. Some are thinking only of light you can see. My first modified car, a 65 Falcon, had the headers painted white. The engine builder told me that white headers keep underhood temperatures cooler. My engine pulled air from the engine compartment. Of course we think of white paint reflecting light but heat is the same as light. It's just not all visible to our eyes. White paint on headers reflects heat inward so more stays contained in the exhaust. Black painted headers are better at dissapating heat which is good if you have a cool air intake setup like a hood scoop.
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I have been painting blocks black for years. Long ago I was teen and a racer told us about heat dissipation and using black paint.
He also said that flat is better than shinny, as it releases heat faster.
On the same hand he stated hood/hood scoops should be light color to reflect heat and white is the best.
The guy was Warren Johnson. I know a GM guy, but he did well in NHRA.
He also said that flat is better than shinny, as it releases heat faster.
On the same hand he stated hood/hood scoops should be light color to reflect heat and white is the best.
The guy was Warren Johnson. I know a GM guy, but he did well in NHRA.
Remember all the leading edges and belly of the space shuttle being black? Now that is some amazing material.
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