Painting a intake to keep it cool

[gretchen/jason]

Well i was watching the usual Horsepower TV show this weekend and saw something i never heard of before . Painting the underside of a intake manifold with white paint to keep the manifold itself cool .

 

Now the paint is the stuff at any autostore like the black headder paint they sell just white . They claimed and ive dealt with this on boats before that the white paint reflects enough of the internal heat from the block to keep the intake air charge cooler then if not painted . Then they went on to say that some racers paint the outside of the manifold flat black to disipate the heat from the top side of the intake .

 

Has anyone tried this at one time . Of course ive heard that painting a engine block black helps disiapate heat faster then say if it was orange or something . I figured id give it a shot to my blower manifold who knows if it works or not i sure dont but whats 6$ going to hurt i figured seeing as im in the middle of a rebuild anyhow .

 

Jason

[RTz]

Doesn't add up to me... painting something a color to gather heat or reject it implies that the heat is a light source.

 

Paint two blocks of aluminum, one white and one black. Put them in a dark oven and they're temperatures will follow each other.

 

Put the same two items with a 500 watt halogen bulb pointed at them and they will become two different temps.

 

Obviously, under the hood, the heat generated from light is pretty well negligible.

[280Zone]

I'm with Ron on this..I can't imagine how color would make any difference when light isn't involved.

[gretchen/jason]

Good point there ,which is why i refered to BOATS . I grew up around boats and the marine enviroment and the reason boats are white is to reflect sunlight ,same goes for boat tops or covers ya never see a black boat top .Me and my grndfather tried it once .

One year we had a blue canvas top it was ok when we were in the Bahamas . Next year a white top made it much cooler when fishing therefore the LIGHT reflectivity . Then of course ive never heard of pistons giving off light as a source of heat .

 

But the TV show only said heat reflectivity they never mentioned a light source inside the engine block . Who knows maybe the ceramic coating just helps shed oil faster so the hot oil doesnt stick to the underside of the manifold .

 

I may try to paint to objects and see what happens . Ill direct a heat source at only the painted side then take temps of the unpainted side one with paint one with out and see what happens . Kind of makes ya wonder why roof top shingles arent white if white reflects heat so good ?

[280Zone]

Dark shingles for roof tops aren't too big of a deal because of the attic. Most flat roofs and mobile homes with no attic are white (or very light in color).

[RTz]

Then of course ive never heard of pistons giving off light as a source of heat.

 

...and I've never heard of 'painting' pistons.

 

Who knows maybe the ceramic coating just helps shed oil faster so the hot oil doesnt stick to the underside of the manifold .

 

 

Now I'm confused... are you talking about ceramics or paint?

[BRAAP]

I’ll give my $.02 on this.

 

As for the oil shedding myth, using glyptol, or any paint does not necessarily add squat in regards to oil shedding value. Before you go beating me to a pulp on this and posting references from all those ridiculous HOT ROD magazine articles, think about it for minute. Once you coat ANY surface with oil, whether it is painted, coated, or as cast, the oil will shed off of itself once it has already been coated in oil! Painting the interior of an engine does indeed help in sealing the pores of the casting and also helps reduce the tendency of casting flash to dislodge under extreme conditions. Also, (as mentioned above), based on the paint or coatings “R” value, you may realize some heat absorption or rejection that the builder/designer deemed worthy in that region. But the primary purpose of painting the interior of an engine is not for oil shedding.

 

Just my $.02

[gretchen/jason]

Paints with certain ceramics in them not totaly ceramic but just headder paint . Im only going off what i heard on tv sorry if its confusing .

Its supposed to be the paint at the auto stores that resist heat like up to 500 degrees kinda like what ya paint a BBQ Grill with . But white

 

Good post BRAAP the show also stated that al those chromed out engines all nice and shiny hold in heat more so then a painted engine . All of this is probably some myth someone started along time ago . I dunno i just wanted oter opinions on the subject is all .

 

Oh i do have a friend that ceramic or sorta jet hot coated the entire outside and inside of his 4 cylinder V Tec block . It cost him a cool 1,500$ but he was told " sorta like the paint deal " That the engine would run cooler coated inside and out eh who knows as he spun all the main bearings after 200 miles as he forgot to torque the main bolts left them loose i should say .

 

Jason

[280Zone]

And yes they were refering to V8 intake manifolds and hi temp paint. So it isn't making sense to me. They went on to say the part about chromed out engines retaining heat, so the best alternative would be to paint the whole engine black, and went on to say they suggested a matte finish! I am not sure what those guys were smoking that day.

[gretchen/jason]

Cool someone who saw the show and could explain it better then me like 280Zone said what were they smoking . But i lived in Texas for 3 years and ever "car guy " i knew told me to paint the engine black to disipate heat faster .

 

Jason

[ihatejoefitz]

"Some overhaul shops claim beneficial cooling effects of black paint on their engine. The theory is that black is a better emitter of infrared (heat) energy. A hot engine in a cold surrounding, radiates energy from the hot object to the cold. The amount of radiant cooling is (generally) dependent upon the temperature of the emitter (engine) and how efficient the engine is at radiating energy -- its emissivity. This derives from Kirchoff's Law where good absorbers are also good emitters. Since black is a good absorber of energy (that's why it's black) it's also a good emitter. A black object emits more radiant energy (cools faster) than a white or gold object that emits less radiant energy per unit of time. Painting an engine black increases the amount of radiant energy emitted by the hot engine to its colder surroundings and it will be cooler than a non-black engine.

 

There is a fallacy to the above argument. Most heat energy emitted by the engine is in the invisible infrared portion of the spectrum. What appears to us as black, white, red, or green in the visible spectrum is not what we would see in the infrared spectrum. Any color of paint that uses organic (non-metallic) pigments is black in the infrared spectrum. For example, white paint emits 90-95% depending upon pigment type. Black emits 96%, blue 94%, green 92% and red 91%. The best emissivity surface coating is acetylene soot at 97%. Painting an engine increases radiant cooling but the color of the paint doesn't.

"

 

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

 

Makes sense

 

-Joe

[G.I.jonas]

Use gold plating like Mclarens,gold is the best heat reflector ever.

[bjhines]

There is radiant "invisible" heat if there is heat at all. Look up "black body effect" to see how color(and finish) can affect heat radiation/absorbtion.

 

 

 

Coatings can act as insulators. They can also act as conductors to increase heat radiated away from an object. There are many types of coatings that are used in motorcycle and aircraft engines that actually help radiate heat away from the object they are applied to.

 

As far as the coatings on the V-8 intake manifolds...

The bottom coating is insulating and reducing the surface area of the bottom of the intake manifold. It also helps the hot oil to drain off faster and impart even less heat to the intake.

The top coating is conductive and usually matte black to increase black body radiation and increase suface area on a nano-scale.

 

White paint was used on header pipes in aircraft as far back as WWII.

[kilten_one]

I make no claims to be an expert and anything even close to it, but the only thing that I can think of that would cause any validity to this idea would be from cooking, the type of pan one uses greatly affects the outcome of the dish, especially in baking. I cannot remember the exact effects off the top of my head and I will edit this to include the effects when I can remember their location, though I recall that the only information regarding this situation was not related to colour rather to finish and metal though the colour of one of the matte metals was mentioned somewhat.

[cygnusx1]

The color of a surface has an effect on the surfaces ability to radiate and absorb radiative energy. Even if there is no visible light emmision, there is radiation from a warm body. On the receiver body (manifold), lighter colors reflect radiation, darker colors absorb radiation.

 

In the application being discussed here, radiation is a very small factor. Most of the energy transfer will be conduction(contact) and convection(hot air), neither of which are going to be effected by color. Conduction and Convection will be effected only by the composition of the coating. Radiation will be effected by color and the composition of the coating.

[BobbyZ]

As was previously stated, there are three kinds of heat transfer: radiation, conduction, and convection.

 

I would argue purely from a theoretical standpoint that this could have a noticeable effect on the temperature of the intake manifold. Whether it is enough to notice a change in the air temps I dont know. The exhaust is going to get hot enough to radiate a large amount of heat energy, a heat shield will reflect most of this heat but the exhaust manifold (or headers) is so close to the intake manifold that I would bet there is a large amount of radiative heat transfer from the exhaust to the intake manifold.

[Ledphoot]

I know for several years I along with several friends raced the local dirt track circuit. We would paint the lifter valley and the intake bottom with white rustoleum to speed oil return and white would not absorb heat like the bare block or darker colors. We painted the exterior of the blocks and heads with a very light coat of black because it was beleived that black dissipated heat and therefore by spreading the heat over a larger surface area it cooled faster.We used just enough to color because layers would insulate not dissapate.

We also would fill the lower portion of the block with "Hard-Blok" to a level just below the bottom of the expansion plugs so it kept heat away from the oilpan and stabilized the block against vibration and coreshift while still maintaining a cooling system. We never painted the aluminum surface of an intake on the outside (top) because it seals the pourous aluminum and keeps it from cooling as quickly. We also always wrapped out headers in heat wrap to keep more heat in the pipes to speed up the exhaust gas velocity which in turn also pulled heat from the cylinders faster. I don't have control data, but I do know all of us that seemed to follow this design always ran cooler and had better longevity at the track.

This was all before the new "coatings" were so readily available. I remember when Jet Hot coatings first appeared and it cost more to coat a set of headers than many of us had in our engines...LOL !

[pparaska]

As has been pointed out, visible light is not needed to transfer heat through radiation. Photons transmit across distances (no atmosphere needed, obviously - or else the sun would not warm the earth) at many different wavelengths, only a tiny portion of which is visible (~0.4 to ~0.7 microns wavelength). The electromagnetic spectrum is huge. If it weren't, the Standard Missile 3 (SM-3) that launched from the USS Lake Erie the other day would not have slammed into it's target, another missile, 100+km above the earth's surface. The SM-3 uses an infrared seeker at it's tip to look for warm things against a very cold sky. Infrared is a longer wavelength than visible light - you can't see the photons that vibrate at those frequencies (have wavelengths >0.7 and up to about 350 microns) - but basically most radiative heat transfer happens due to those photons.

 

There are coatings that are black yet have a VERY low emissivity, like 0.15 or so. An emissivity of close to 1.0 is what most natural substances have. It's not that simple though. Texture, chemistry and other things make it not so simple as to say one color is that much better than another.

 

Techline coatings has different coatings for the bottom and top of the intake manifold. There is more to these than just emmisivity if I recall correctly

[Tony D]

Some strange facts from the Air Cooled World:

Long has the time been that Corvair People paint the top half of the pushrods (under the head) with white ceramic based paint to reduce oil temperatures. I thought "B.S." but damned if I didn't notice the Finch-Claimed 10-15 Degree reduction in oil temperatures. Did the same thing on my VW, and sure enough, same / similar reduction, though for some reason the VW guys aren't into painting their pushrod tubes like the Corvair guys are...probably has something to do with a properly designed VW oil cooling system compared to the Corvair...

 

Similarly, Gene Berg was big on lightly painting, or having the case anodized flat black for heat reduction. Similar kind of oil temperature reduction. Milspec Anodizing somehow helps in the transfer/emissivity of Aluminum Cases. Another strange one because HP VW guys do the case Painting/Anodizing on an Aluminum/Magnesium AS41 Casing----while the Corvair Guys with a real Aluminum Alloy case don't.

 

As for Techline Coatings, they are about 20 minutes from the house, and a division of our company uses their abradable coatings in rebuilding Lysholm Screw Compressor Elements, as well as some 'side work' dealing with the Project Manager's Nova... Probably one of my Manifolds will get done there some time in the future (our shop) as they have all the facilities to properly apply the Techline Stuff, and the offer has been made to 'send in whatever you want coated'---terrible when you have a fellow who is a gearhead, and has access to production coating equipment ! LOL

[DavyZ]

The owner of Techline Coatings was a member here for a long time when the forum started. Good products from what I have read.

 

Davy