Heat deterrent inside or outside?

[Theshandman]

Getting ready to close up the foot boxes. I want to install heat protection of the ‘thermal-tec’ and its ilk variety (not Lizard Skin style protection). All my alum panels are black texture powder coated so I’d like to keep that look in the engine bay. Does ‘stick-on’ heat material typically get applied outside the foot box or inside? Seems to me if a silver reflective type of material is used, it would necessarily go outside which would detract from the black look. I’ve never used anything like this so any suggestions are appreciated.
Art

[CaptB]

My vote, for what it's worth, is inside. That way you keep the exterior clean.

[cob427sc]

I've always installed it inside, then cover with your carpet. In the engine compartment it would not have a good appearance and would be subject to damage when your working on the drivetrain. I have in some instances actually put the center tunnel/tranny cover on the outside or down side as I wanted to have a smooth surface for the upholsetry, but put it inside under the carpet in the floors and firewall areas.

[Theshandman]

Thanks guys; I was hoping to hear this. :)

[seagull81]

Don't forget to install something between the foot box and the body. A lot of heat comes through there.

[edwardb]

You'll get lots of opinions on this and see lots of builds where guys are putting heat resistant whatever on the outside, up to and including panels with standoffs, etc. Let me just pile on the previous posts and say that I've only put insulation (and carpet) on the inside of multiple builds and left the engine side clean. I've never had a heat issue. Have used various products. Lizard Skin, Damplifier Pro, Dynamat to name three. All have performed well. I will add that you also need to seal the cockpit from air from the engine compartment. Very important. Even small leaks will feel like you left the heater on. For the Roadster, one of the big areas to address is the gap between the body and footboxes on each side behind the door hinges.

[NiceGuyEddie]

I've seen a lot of race cars with the insulation outside the footboxes, but otherwise putting insulation over the footbox instead of under the carpet is like putting dress socks over your shoes.

You'd also be hard-pressed to wipe clean insulation if it's exposed.

[JohnK]

I'm one of those that added insulation to the outside of the footboxes. I will echo what everyone else has said - if choosing to do one or the other, definitely put it on the inside under the carpet. In my case, I installed Lizard Skin heat and sound insulation on the inside. I chose to also add stainless steel heat insulation on the outside of the footboxes because my headers have catalytic converters on them. Is it necessary? I don't know... probably not. But here's what I know... it's far easier to install it before the engine goes in than after, and there's no real harm to it. I kept it low enough that it's not really visible with the engine installed, and it's a rigid stainless steel so easy enough to wipe clean if needed.

https://thefactoryfiveforum.com/attachment.php?attachmentid=151521&d=1627956429

[Fman]

Art what engine are you running? I do believe your engine type (Coyote vs 427/pushrod) will play a factor. FWIW I’ve got 3k miles on my car with a Dart 427 and FFR stainless ball flange headers. I had issues with excessive footbox heat. I lined every panel in my car with Thermo Tech insulation and still felt like I was getting too much heat. I ended up adding the sticky heat shield on exterior firewall panels. I also wrapped my headers with DEI titanium, added a couple blowers and stuffed a bunch of foam insulation in the door gaps. I also just recently removed the Breeze upper radiator cover which is definitely helping push more fresh air into the engine compartment when the car is moving. All these items have made a difference from where I started.

I would tell you do everything you can to prevent heat in your footbox. It is not expensive to do this and will only help your footbox temps.

[BEAR-AvHistory]

Getting ready to close up the foot boxes. I want to install heat protection of the ‘thermal-tec’ and its ilk variety (not Lizard Skin style protection). All my alum panels are black texture powder coated so I’d like to keep that look in the engine bay. Does ‘stick-on’ heat material typically get applied outside the foot box or inside? Seems to me if a silver reflective type of material is used, it would necessarily go outside which would detract from the black look. I’ve never used anything like this so any suggestions are appreciated.
Art

It goes on the outside facing the heat. My choice was ThermoTec on the outside & Reflectix on the inside under the carpet. Only heat you will get is from the sun cooking you.:D Be sure to seal all upper body leak points, they are easy to find, to keep engine heat out.

About the "look" of the panels. Plain uncovered look better but on a Coyote install there is not much panel to look at. 7 years on the road as a DD

[Theshandman]

Art what engine are you running?

Fman, I went with a BPE 347 / FI / TKX combo, Gasn polished headers and (touring) side pipes. If wrapping the headers is one part of the heat solution and it seems to me that it is, I kinda hate it I got polished headers! Then again, if I only drive in cold weather... well, that's not quite an attractive option, is it? Blowers, eh? How did you arrange them? Foot box blowers I presume? Did you take the inlet at the forward brake vents? And interesting note on the Breeze rad cover; I was thinking of ordering one. Maybe not now. Hmmm...
Art

[Theshandman]

...putting insulation over the footbox instead of under the carpet is like putting dress socks over your shoes.

Ha! Good one!

[Hacksaw84]

I did both inside and out and partly wrapped the headers with Heatshield Armor. None of it is obvious once the car is all together. I have no footbox heat issues. Plus I also have a fresh air vent kit with fans if needed. Its probably overkill but I like it...

164050

[Fman]

Fman, I went with a BPE 347 / FI / TKX combo, Gasn polished headers and (touring) side pipes. If wrapping the headers is one part of the heat solution and it seems to me that it is, I kinda hate it I got polished headers! Then again, if I only drive in cold weather... well, that's not quite an attractive option, is it? Blowers, eh? How did you arrange them? Foot box blowers I presume? Did you take the inlet at the forward brake vents? And interesting note on the Breeze rad cover; I was thinking of ordering one. Maybe not now. Hmmm...
Art

Art, You can wrap your headers down the road if you want while they are on the car that is actually what I ended up doing. If I were doing it over I would send my headers off to have them ceramic coated before installing them. Easy to do now rather than pulling off the car later. For blowers I added a 4" bilge blower on each side under fender that blows out towards the side vent. As I mentioned I also removed the upper Breeze radiator cover and I can already tell this is adding a lot more air flow under the hood into the engine compartment. I know some guys use a stick on liner (thermo tech) and also do lizard skin on the firewall and cockpit area, I would definitely recommend this and wish I would have also done this.

The 347 will more than likely put out less heat than a 427, I have over 500 HP so this plays a factor. I know my headers are 450+ degrees (heat gun). This is just my opinion on this as some have mentioned they don't seem to have any issues with footbox heat. I also drive in shorts all summer during the warmer months.

[nucjd19]

I have the BPE 347/ TKO600 and my foot boxes don't seem to get hot. I used Breeze Koolmat insulation and it has worked out very well. For me it was not the easiest to install and was more expensive than the other options but created a very nice "feel" to the carpet once it was installed and IMO has done a very nice job. Like Fman said the 347 has a little more space in the engine bay compared to the coyote and the 427 and that air gap really really helps. I have not sealed up my gaps from the engine into the cockpit yet as I am in gelcoat so I get some heat from the engine compartment coming in when I pull off from a stop sign but that will go away once it is in final paint and the gaps are sealed. I really think you will have less of an issue than you think with the 347.
https://thefactoryfiveforum.com/attachment.php?attachmentid=142385&d=1612924693

[Hoooper]

If it is INSULATION it doesnt matter what side you put it on, from whatever the innermost surface is to the outermost surface the whole sandwich acts as an assembly and the R values of the various materials that are sandwiched together all add together, doesnt matter which side the best R value starts on. On the inside makes sense for insulation since you can then cover with carpet and it wont be seen and will be protected. If its heat REFLECTIVE it needs to face the hot side.

[John Ibele]

If it is INSULATION it doesnt matter what side you put it on, from whatever the innermost surface is to the outermost surface the whole sandwich acts as an assembly and the R values of the various materials that are sandwiched together all add together, doesnt matter which side the best R value starts on. On the inside makes sense for insulation since you can then cover with carpet and it wont be seen and will be protected. If its heat REFLECTIVE it needs to face the hot side.


While trying avoid being a total bore (and likely failing), a few more comments on Hoooper's input. A comprehensive approach to heat transfer would at least consider the 3 paths through which that occurs: conduction, convection, radiation.


Insulation applied to the interior of the footboxes (Thermo-tec, similar products, even Lizard Skin) cuts down on conduction of heat through the footbox panels. It also provides sound attenuation and is commonly used for good reason. Thermo-tec mentions reflection of radiated heat in their marketing, but no product is going to reflect radiated heat from a source outside the footbox when it's applied on the inside. Don't let that deter you from putting it on the inside ... a good product for heat insulation and sound deadening, and that aluminum film is a fine backing material to apply the carpet on.
Convection is addressed by Paul's comment. Make sure you plug up all air gaps between footboxes and the engine bay.
Radiated heat travels across open air from source to destination. In this case the primary culprit is the headers, both because of surface temperature and proximity to the footbox surface. Two options: address at source with insulation (wrap, coating ... reduces surface temp and resulting radiation), or address with reflective panel at destination.


Yep, wayyy more than you asked for. You're welcome :rolleyes:

Previous comments have touched on all of these. Based on recommendations from those with way more experience than I have, I'm doing 1 and 2. I'll keep 3 in mind if I don't like the result, but ... uh ... I'm in Minnesota. I'll probably just turn the heater down first. :cool:

[Theshandman]

Yep, wayyy more than you asked for.
Not at all, John! Great stuff, very informative.
Thanks to all who helped me (and undoubtedly others) understand this complex issue.
Art