Black engine blocks. Why are they cooler?

[bull]

This was discussed either here or on the old site. It was concluded, and reinforced by expert opinion, that engine blocks painted black (and radiators too) somehow keep the engine cooler. I don't remember ever learning how or why this is possible so if anyone remembers the discussion or just plain knows how this works, please let me know.

Here's a baffling discussion on the topic: http://answers.google.com/answers/threadview?id=711843

[alfanta]

I never was part of the convo, but I would bet it has to do with the fact that black absorbs/releases heat more quickly than any other color. imagine wearing a black T-Shirt. It heats up really quickly in the sun. Based on the laws of chemistry it should absorb heat as quickly as it releases it. Therefore it would also dissipate heat more quickly than any other color.

but I haven't taken chemistry since High school. 

[bull]

I never was part of the convo, but I would bet it has to do with the fact that black absorbs/releases heat more quickly than any other color. imagine wearing a black T-Shirt. It heats up really quickly in the sun. Based on the laws of chemistry it should absorb heat as quickly as it releases it. Therefore it would also dissipate heat more quickly than any other color.

but I haven't taken chemistry since High school. 

He neither, and you remember way more than I do.

[bull]

I'm going to throw something out here and see if it sticks. The heat outside a running engine is going to be lower than the inside, right? So then if the color black absorbs heat it must equally radiate it and exchange it with cooler air if air is always trying to equalize its temperature, right? Therefore, the black surface will absorb the heat generated on the inside (since it's greater) and radiate it outward in the direction of the air that's cooler.

Also, would an unpainted engine stay cooler than a black one?

[Rocky]

While we are at it, why don't we contemplate the male nipples?   

It's friday.  Have a beer and relax.   

I think Race Hemi Orange blocks are cooler anyway.   

[Charger1973]

While we are at it, why don't we contemplate the male nipples?   

It's friday.  Have a beer and relax.   

I think Race Hemi Orange blocks are cooler anyway.   

I think my block is going to be silver when the time comes...

[bull]

While we are at it, why don't we contemplate the male nipples?   

It's friday.  Have a beer and relax.   

I think Race Hemi Orange blocks are cooler anyway.   

My days off are Wednesday and Thursday so today was Monday.

[bull]

While we are at it, why don't we contemplate the male nipples?   

It's friday.  Have a beer and relax.   

I think Race Hemi Orange blocks are cooler anyway.   

I think my block is going to be silver when the time comes...

Funny you say that because I just read that silver is the worst for heat dissipation. Sorry.

[Charger1973]

Go figure.     Thats ok my minds not 100% made up yet.   

[Ghoste]

Petty used to run his Hemi blocks unpainted, so...?

[ds440]

 

I always was under the impression that the color black's heating/cooling abilities were directly related to its relationship to light (i.e. sunlight).  I have NO IDEA if that's actually correct.  And since an engine under a closed hood doesn't receive direct sunlight, the difference in temperature would be nominal(?).

I don't see how color can absorb temperature from anything other than light, unless it's the chemical make-up of the dyes that are used that cause said reaction(?).

I have heard of race teams lining the engine bay with gold sheeting in order to DISSIPATE heat, but never of painting it a certain color.

Kind of on a related subject - is it true that you should never paint an aluminum block or aluminum heads, because it will not allow the aluminum to release engine heat?  Anyone?  Anyone?  Bueller?

[70charger_boy]

The Mythbusters already proved it

[ds440]

Just found this....

http://www.sacskyranch.com/paint.htm

[alfanta]

well silver would probably be one of the worst because of the make up of the paint. since its not pigment, but more of flakes and clear coat, I would think its going to insulate very well. Not what you want.

Light is just a small part of the visual electromagnetic spectrum. The theory why black absorbs it so well is because it doesnt reflect anything whether it is light, heat, whatever. Try this, I dont know if it will work or not, but lets try it. Paint two sheets of metal. One black and one white. Set an iron on the black one and let it get hot. take it off and see how long it takes to cool. then do the same with the white one. Im willing to bet the black one gets cooler faster.

again, I am by no means an expert in the subject, but i was a science/math geek in highschool so...the only thing that makes me curious is why baroques are black? probably so they dont change color with the heat and charcoal thats around them all the time.

And i would NOT paint aluminum. It dissipates heat so quickly that the paint probably would slow it down.

Insulating the inside of an engine bay with gold would work. Gold is one of the best conductors we know of hince why it is used as connectors for electronic components such as high definition dvd players, and some high end stereo equipment(I cant remember if silver is actually better or not, but I have read that the gold is just a marketing ploy to get consumers to pay more). since it doesnt really tarnish like steel, copper, or even silver, it wont corrode into an extra layer of insulation. but that sounds expensive 

Aside from black I thnk that any other color of paint actually would insulate the heat in. I do think though that its a very minimal difference, otherwise the car manufacturers would have every block painted black so they can put even smaller radiators in them. Does anyone know if the air cooled VWs had painted blocks?

-RJ

[alfanta]

Just found this....

http://www.sacskyranch.com/paint.htm

well, I was right about the theory of black, but Black paint isnt truly black then is it?
guess I was wrong about the gold though. But I did say it was a minimal difference !

So YAY! Paint it whatever color you want. within reason.

[bull]

The Mythbusters already proved it

Proved it wrong or right?

[Ghoste]

Proved that someone watches their show.

[Steve P.]

Proved that someone watches their show.

What show?? 


I am no scientist, but I did sleep in a Holiday Inn Express once..   

This was something that was put to the ROUNDY_ROUND guru's a few years back. According to them BLACK was the best color for heat dissipation.  However, the cooling guys didn't like the rads. painted black as the cooling fins did not have enough room between them for good air flow WITH ANY PAINT...  They like clean aluminum for the best cooling rads.

I only remember this because VegasMike was having overheating troubles at the same time as this show.. AND I stayed at the Holiday Inn......   

[Ghoste]

Is Holiday Inn a reality show?

[70charger_boy]

Is Holiday Inn a reality show?

Holiday Inn makes the funniest commercials

[bull]

Is Holiday Inn a reality show?

Holiday Inn makes the funniest commercials

And then you reply without annswering my question...

[70charger_boy]

Is Holiday Inn a reality show?

Holiday Inn makes the funniest commercials

And then you reply without annswering my question...

oh, i can't remember if they proved it right or wrong sorry

[bull]

Is Holiday Inn a reality show?

Holiday Inn makes the funniest commercials

And then you reply without annswering my question...

oh, i can't remember if they proved it right or wrong sorry

[RoscoePColtrain]

From what I remember from my Thermodynamics class, no color is capable of absorbing heat, but light yes, infra-red light to be exact.  The colors you see on a GL for example is white light hitting the car, almost every color being absorbed, and you see the car as orange, becasue its the only color not absorbed.  The color is responsible for the absorbtion of light.  The absorbed light is turned into heat energy.  Now the conduction of heat depends on the characteristics of the metal, not dependant on the color.