I got to thinking today about surface temps of headers. Has anyone used an IR gun to measure just how warm your headers get? I am REALLY curious how the temps compare between ceramic type coated and stainless. Hell, let's throw in factory manifolds too. My thinking is geared toward underhood temperature control.

Anyone have numbers? Or the means to get numbers?

 

Ceramic usually does stay abit cooler underhood than uncoated.

Mild steel header can read 600-700 deg after awhile of run time. At wot depending on setup they can be 1200 or more...glowing orange.


Ceramic will cool on the surface faster than uncoated

 

Kwkenuf - I haven not done so on a 3rd gen, however, on my 70 Buick Stage1 I (Buick 455 stroked to 470 - 582hp, 602 tq) used my thermal heat gun. At idle, the temps were 250-350, plug 4 and 6 were exceptional. They were 450-650, I reset the lifters on 4 & 6 - they were a bit tight. They still run in the low 400s - when I get the 84 Bird back from the rear end shop I will see what they are. Byron

 

Headers can easily get in to the glowing orange (1200*F) range, but typically are around 400* idling, abut 600* running (but a lot of that has to do with the tune, you can retard the timing at idle and get them to glow in a minute or 2).

Ceramic used as a header coating is supposed to be an insulator, but a lot just come down to something that is a barrier that will survive the temps, so how much cooler the engine bay ends up will likely depend on who's coating it is.

Most header ceramic coatings will not dissipate heat faster, the tubes stay cooler by keeping more heat in the exhaust (insulating).

 

Trying to remember where I saw it, but they were showing the differences in insulating properties between the usual header materials. T304 stainless about twice as efficient at keeping the heat in the exhaust as mild steel was. I think the Stainless did better than the coated headers did.

Really wish I could remember where I saw it. Bugging me now that I can't quote it.

 

Theres possibly some useful info in here;

 

I'd like to read that, if you recall where it was written.

So then we might surmise that ceramic coated stainless headers might make a significant difference?

 

I'm game for anything that keeps the heat out of the engine bay.

My 2210's are uncoated the heat under hood is downright unbearable after a long run. Especially under any real load.

 

I do know for a fact that 316 stainless steel will glow red at 1250*F, I have seen it several times on several different diesel engines. even cast iron will glow red at that temp. In the diesel world, at least big diesel (IE marine diesel/diesel electric) at above 1200* no coating will really stand up to the temp.

 

I can roughly correlate Orr's #s; most I've seen are a shade lower at idle and low load, but right in that same ballpark. A well-tuned atmospheric hydrocarbon engine will almost always have 1200 - 1400° exhaust (more if The Force is invoked). Probably has a great deal to do with environmental conditions; how much air is flowing over them, the tune (mixture) which determines how hot the exhaust is and/or how much liquid fuel (coolant) is in it, IGNITION TIMING which determines whether combustion has completed before exhaust starts to emerge from the valve, and so on.

Stainless has a bit less than half the heat conductivity of mild steel depending on the alloy, some alloys a good bit less. http://www.engineeringtoolbox.com/th...ity-d_429.html Most headers would be a 400 series alloy which in general conducts a bit better than 300 series but you never know until you know. Ceramic coating reduces heat conductivity even more; I don't have #s, not least because of the lack of precision involved, but every bit helps. On mild steel it probably halves the HC roughly speaking, meaning, probably reduces it by a third or so on stainless.

There's no direct correlation between heat conductivity and temperature, since there are so many other factors; but it's safe to generalize, the lower the HC, the lower the temp will be.

Ceramic coated stainless headers actually release about the same amount of heat into the environment as manifolds as far as I can tell. Maybe even less. Hard to say, as many external factors as there are.

I have ceramic-coated SLPs in my Camaro and coated ... something else stainless ... in my truck. Both of their underhood temps are not too much different from when they had manifolds.

ANYTHING will glow red at 1250°. As a physicist, I can tell you we call that phenomenon "black-body radiation". https://en.wikipedia.org/wiki/Black-body_radiation Doesn't matter what the material is.

 

Like he said, but also, If you are using exhaust insulation or "lagging" as we call it in the marine world. it will tend to "raise" the temp becuase the metal cant disipate the heat.

 

Right: it might "raise" the temp of the metal itself, down underneath that blanket of whatever, but LOWERS the heat transferred into the outside world.

Physics - going back to the FIRST PRINCIPLES of how things work - always has the correct explanation.