What are good materials for that and how to make it most efficient? I was thinking about just bending a sheet of aluminum, but that seems kind of flimsy.

Another option is to do ceramic coating on the headers, but I don't know how effective that would be, and frankly that's not really in the budget anymore. At least for now.

 

ideally you want something like steel that will block the heat and not absorb it.

back in the day we used to use steel and line it with header wrap, you can sew it on with safety wire

 

Jegs has header wrap if you wanted to wrap the header. If that doesn't drop the temp to your liking use steel for the shield, aluminum will act as a heat sink and transfer it directly to your floor.

 

The RB header shield is aluminum, as is the stock heat shields in most places. If you can go with the ceramic coating, have it done on the inside of the headers first, then the outside if you can afford both.

 

Yeah, I was thinking about how the stock shielding is aluminum. But I also think ultimately the idea is to reflect heat down to the ground, away from the intake manifold. Since the sheet of metal would be fairly thin, its conductivity might be a lesser factor. In that regard the metal itself might not even be as crucial as the surface facing the heat source. The more heat it reflects, the less it's going to heat up. Now, I'm not a physics major, so I don't really know what surface finish or coating would be most effective at that. I imagine something shiny would do a better job than something dull, but that's about it. In fact, if the side facing the intake manifold could absorb heat, that'd be even better.

As far as ceramic coating, IIRC the local place that does it coats both inside and outside. It's been a while since I've had them coat a set of headers, so I don't remember, but I think that's how it goes. Two things that concern me regarding the ceramic coating vs. heat shield are first that coating would trap the heat inside the exhaust, making the exhaust ports hotter, instead of dissipating heat away from the engine, and second that it's quite pricey.

And no, I'm not going to do header wrap.

 

what shields are aluminum? all of the ones around hot things are steel, with insulation

 

Header wrap rots out headers. Holds way too much moisture for my liking.

 

Whats wrong with painting the headers before you wrap them? Then you have the best of both worlds.

 

Or I could paint headers, wrap them, AND make a heat shield. It'll be snowing under there.

 

Yes, the more shiny/mirror like, the more heat it reflects.

The hotter one can keep the exhaust gas, the more velocity it maintains. Cooling allows the gases to expand which in turn slows them down, thus reducing hp.

Unless I'm having a major brain fart, some of the shielding is aluminum. I recall seeing both steel and aluminum shielding. Even the large insulated one over the main cat.

 

I modified a small air bake cookie pan

 

I have had my header wrapped for two years and have yet to see any moisture on it at all. It does not get sprayed by road wash and when the car is running it would be too hot and any moisture would just evaporate. There has to be some other explanation for headers with wrap to be breaking.

Header wrap does a great job of reducing the underhood temps. I can touch my header while the is car running with the wrap on. It's also fairly cheap. I think I payed $30 or so for the amount of wrap I used, although the shop I bought it from takes back what I don't use.

 

I think the explanation could be that in humid climates there's moisture in the air, and it would condensate on header wrap and seep through to the metal and get trapped. And since most of the time the car is off, rather than on, the header is cold and does not force the moisture to evaporate.

 

84 Stock, I think you're on the right track. As I was reading this, I was thinking that you need to fab a shield from two thinner sheets of metal with an air gap between them (metal standoffs strategically placed to maintain space); but the Air Bakes did that already - brilliant!
Modded Air Bake baking sheet - now that's right thinking. What you need is an air layer between two sheets - that's what Air Bake baking sheets give you. The hot side stays hot, the cool side stays cool.
No matter what your heat shield is made of, it will absorb some heat. I believe that steel will heat soak (and stay hot), whereas aluminum will quickly dissipate it (cool quickly). Why not have that cooling air layer to interrupt heat transfer?

 

I was also thinking of making one of these myself, does anyone know how the RB shield is attached to the engine?

 

I think most shields use exhaust studs.

 

Huh. I wonder how many layers I can fit in there.

 

that might be right? i HAVE the sheilds, in storage, so i cant just go look...

 

Here's the respeed unit, made of aluminum, easy to install, looks great and is inexpensive:

 

I can't use the Re-Speed shield, because I'm running stock intake manifold with actuators and all that. Billy used to have the shield that works with stock manifold, but it's no longer available due to manufacturing costs.

Oh yeah, and further on the header wrap issue. Seems another reason that it damages headers is because it prevents metal from shedding some of the heat, and as such the header reaches much higher temperatures and corrodes and breaks down a lot quicker. Especially on rotaries and their massively hot exhaust. Naturally if moisture gets in there and causes rust, excessive heat accelerates the rusting process as well. So ultimately it's better to let the header breathe and dissipate some of that heat - that way it'll last longer.