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Hipster Lawrence
12-07-2011, 12:54 AM
Any science nerds here?

I was going to wrap my header. I changed my mind. There is a can of black header paint on the shelf. My boss is adamant that I shouldn't paint my heat shield black, says it will make it less efficient/not work.

I can understand his point but really is it going to make that big a difference? I don't want to buy a can of paint just to do my heat shield.

You think regular engine paint will hold up on an exhaust heat shield? I have some silver engine paint.

vip09
12-07-2011, 01:55 AM
I don't think it makes a difference in this case. Dark colors do absorb insolation (incoming solar radiation) better than light colors. The insolation that is absorbed by an object is then released through radiation.

Car_Barn_Bandit
12-07-2011, 02:08 AM
I'm sure the difference will be within 30 degrees or so. Not sure if that has any long term effects, but they are typically silver to reflect as much as possible.

Sent via Imperial Comlink

klapa
12-07-2011, 02:51 AM
I don't know - when you say "black body radiation" that makes me think about the heat radiator we would use at times for testing automotive climate control systems.

Radiated heat is different than absorbed heat - I would not think it would make much difference - though I don't know - but a 30 degree difference seems extreme to me.

I would think for something like a heat shield - the main consideration would be the surface area of the metal - much less the coating.

On another note - I have not yet found a "engine paint" that will hold up to the heat of a block without peeling in the long term - much less the heat of an exhaust manifold. Perhaps others have had better luck than me.

As a matter of fact - looking back on my motorcycle experience with exhaust - only the best triple chrome plating holds up over time without at least turning blue.

Again - perhaps others have had better luck.

mckenziejr
12-07-2011, 02:58 AM
i used aluminum foil tape on the underside of the heat sheild works great

Hookecho
12-07-2011, 03:05 AM
I used silver in color ceramic caliper paint on my heat shield and it still looks great after 4000 miles. I used a whole can and laid it on thick.

Car_Barn_Bandit
12-07-2011, 03:10 AM
Radiated heat is different than absorbed heat - I would not think it would make much difference - though I don't know - but a 30 degree difference seems extreme to me.

I honestly can't see it being more than that temp. That is my extreme max guess based on tests we did in school with solar heat absorption. Black paint helps, but it's marginal unless you can get a true chrome finish.

Ultimately a special black coating on copper in a vacuum tube got us the results we wanted...


On another note - I have not yet found a "engine paint" that will hold up to the heat of a block without peeling in the long term - much less the heat of an exhaust manifold. Perhaps others have had better luck than me.

I have found some success with proper prep work in VHT's paints. If used with a ceramic primer on a CLEAN surface (acid dipped or bead blasted) then a ceramic base with a ceramic clear, I could get good results. Too much effort when powder coating can be done for less hassle.

Hipster Lawrence
12-07-2011, 03:19 AM
Thanks for the input guys. I think I'm overthinking it. I'll try and get a before and after temp difference reading.

As for painting an engine. As long as its prepped properly. (blasted or tanked or both and degreased about 5 times. And primed with a good etching primer you can use just about any paint. The custom guys here all use regular 2 stage car paint with awesome results.

Header paint lasts about 20 miles on headers. But I know from experience it will hold up fine on a heat shield.