David K Posted October 11, 2003 Share Posted October 11, 2003 Its time to spray my f54 block thats on the stand. Whats the best color other than Nissan baby blue or white to reflect heat? I was thinking a flat grey to match the head would be nice. Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted October 11, 2003 Share Posted October 11, 2003 Huh? !M! Quote Link to comment Share on other sites More sharing options...
DavD3 Posted October 11, 2003 Share Posted October 11, 2003 I red somewhere black is the best to dissipate heat. Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted October 11, 2003 Share Posted October 11, 2003 I'm a few sheets to the wind, so here are a few quotes: Reflection of heat and dissapation of heat are two diferent things. Any paint on a motor should build heat since paint is not as good a heat sink as metal and thus an insulator and thus keeps heat in (albeit to such a small extent as to be immeasurable in my opinion) I do know that a white radiator will run hotter that a black one. A radiator's job is to COLLECT heat from the motor then dissipate it through convection and radiation Question. How does the inside of the engine know you painted the outside black in order to know it should push heat to the outside? Why would the motor need to know what color it was painted? if you are drawing heat away from the surface the ajacent cast iron molecules will 'share' thier heat with the ones close to surface. Heat is conducted. So 'if' Kirchhoff is correct ( and let's assume he is ) we know that blackend surfaces are excellent at absorbing, we then also know that they are excellent at emitting. The engine doesn't need to know what color it is. The paint will emitt and cool itself witch will draw heat from the motor. You would have to explain how the radiation outwards would be sped up by applying a low conductive material like paint to the outside. The internal heat has no idea that paint had just been applied to the outside and for some reason now needs to accelerate its movement to the outside of the engine. The rate at which a body radiates (or absorbs) thermal radiation depends upon the nature of the surface as well. Objects that are good emitters are also good absorbers (Kirchhoff's radiation law). A blackened surface is an excellent emitter as well as an excellent absorber. If the same surface is silvered, it becomes a poor emitter and a poor absorber. Make what you want of those. !M! Quote Link to comment Share on other sites More sharing options...
David K Posted October 11, 2003 Author Share Posted October 11, 2003 meant reflective, doh, late night.....i spent all day working on the engine, i wanna get the color the best i can, even if the result is minimal. I know about black body radiation. My black zx was very hot in the daytime, and the white 77 stayed a world of difference cooler. Just applying these to the engine, not sure if i would get the same results under a closed hood. Quote Link to comment Share on other sites More sharing options...
CruxGNZ Posted October 11, 2003 Share Posted October 11, 2003 If you think you may have cooling problems, invest in a better radiator and leave the worries behind. Paint your engine and head whatever you like. Just don't use Day Glow Orange !M! Quote Link to comment Share on other sites More sharing options...
David K Posted October 11, 2003 Author Share Posted October 11, 2003 let me go to sleep and read my stupid post tommorow morning. I now remember i had a discussion about this topic with a friend a while back and i knew the facts......sheesh Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted October 11, 2003 Share Posted October 11, 2003 You're right - the answer is black. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 11, 2003 Share Posted October 11, 2003 You describe getting "reflective" paint because your Z got hot in the sun. But your engine isn't going to get hot from the outside. It will be cooled by the outside, since the underhood temps should in every case be lower than the water temperature. So you want the block surface to get as much of the water temp heat as possible, so the air coming through the radiator and past the block can take it away. The answer is black. Speed Racer is right. You probably read black was best in How to Hotrod, BTW. BRE used to paint all of their motors black. Jon Quote Link to comment Share on other sites More sharing options...
Guest greimann Posted October 11, 2003 Share Posted October 11, 2003 I third it, Black. You want the heat to leave the block, not be retained inside. Quote Link to comment Share on other sites More sharing options...
260DET Posted October 13, 2003 Share Posted October 13, 2003 Yes, black. And if you really want to be fussy a very light coat of flat black. But I wouldn't bother. In fact, for the little difference it makes, any dark colour should be OK unless your engine cooling is extremely, extremely marginal. Quote Link to comment Share on other sites More sharing options...
baddriver Posted October 13, 2003 Share Posted October 13, 2003 It pays homage to the beauty of physics and the symmetry of nature to note that good absorbers are also good radiators. Thus, you want to paint your engine whatever color would make it heat up the most in the sun. Black, my friend, is the answer. I would also like to note that the best radio antenna is one that is identical in form to the tranmitter, for the same reason. Later, Jeff Quote Link to comment Share on other sites More sharing options...
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