A little unscientific research on Footbox Heat

[Ted G]

As I am contemplating my build starting a about two months, I am very concerned about footbox heat. Travis (FMan) has brought this up several times on this forum so I thought I'd have little fun. Here in Northern California we have pretty hot days and running my DART 427 headers within inches of the footboxes, I decided to do some research. Although I am not a scientist, I came up with some interesting variable in the transfer of heat with this idea that I may have seen on the forums.

I made a little video about the whole, unscientific study in my kitchen with my stove, some steel panels, CoolIt Thermotec, and an idea. Here is the about 12 minute video if you are so inclined.

https://www.youtube.com/watch?v=-9YgrlhVaDs

This is my first youtube post, so I hope it works.

My next study will be the same, but with much higher heat from my stove.

Ted

[edwardb]

Interesting. This is one of the most discussed topics on the forum and everyone seems to have their "I burned my feet riding in a Cobra" story. Real world experience: Good quality insulation (I've used various name brands including Lizard Skin) on the inside of the footboxes + carpet + making absolutely sure no air from the engine compartment is getting into the cockpit/footboxes = no heat issues. No sense of heat from the engine, headers, whatever. Granted, Michigan weather is on the mild side compared to some. But we still have 90+ degree high humidity days and I've driven in them. No difference. Heat exhaustion from the elements and sun. Not the car. This is based on three Roadster builds and one Coupe build over the past 12+ years and thousands of miles. I personally like the engine compartment clean (e.g. no heat insulation on that side) and have found no reason to complicate things with added insulation sheets on standoffs, etc. Some add fresh air vents into the footboxes, and I've done that too. Feels OK to have air moving on a hot day. But not sure it changes anything all that much.

[zee]

That was pretty cool. I would’ve loved to see Celsius as well, I had to keep converting it manually :-). I wonder if it’s possible for you to add lizard skin as well in your tests. Looking forward to more videos.

[Gordon Levy]

In the couple hundred of these cars we have done footbox heat has never been a real issue. As long as you get a good seal between the body and the footbox it is fine and comfortable.

[john42]

In the couple hundred of these cars we have done footbox heat has never been a real issue. As long as you get a good seal between the body and the footbox it is fine and comfortable.

In my Challenge car that I've only had about 6 months now and raced only once on a really hot day (90F) the footbox only got annoyingly hot when I was sitting still. The moment I started driving it cooled off really quick. Mine has no heat shielding whatsoever or vents on the footbox. (the vents from the front go to my breaks!) My headers are however heat wrapped from the sparkplug area down about 12 inches. This is more for the sparkplug wires. So ya I agree. If the footbox is good and sealed it is comfortable. I'm also the type of person who HATES hot feet. I'll wear sandals in the New Hampshire winter even...

[Ducky2009]

I added heat shields between the headers and footboxes. Learned from round track racing long ago how hot it gets inside.
Multiple pics in the gallery. Wrapped around the corner on the PS. Not enough room on the DS. Added insulation under the carpet too, like everyone else.
https://thefactoryfiveforum.com/album.php?albumid=1085&attachmentid=67425

[BEAR-AvHistory]

Well sealed against air leaks.

Thermo Tec on all outside surfaces that face heat including the panels under the doors & inside the transmission side sheets & cover.

REFLECTIX Attic aluminum/bubble/aluminum sandwich insulation on all interior surfaces including rear bulkhead

Carpet all interior surfaces,

Daily driver in Carolina summer sun with no engine, header, sidepipe heat intrusion. Plenty from the sun.

[Hoooper]

In my Challenge car that I've only had about 6 months now and raced only once on a really hot day (90F) the footbox only got annoyingly hot when I was sitting still. The moment I started driving it cooled off really quick. Mine has no heat shielding whatsoever or vents on the footbox. (the vents from the front go to my breaks!) My headers are however heat wrapped from the sparkplug area down about 12 inches. This is more for the sparkplug wires. So ya I agree. If the footbox is good and sealed it is comfortable. I'm also the type of person who HATES hot feet. I'll wear sandals in the New Hampshire winter even...

Completely agree, footbox heat was never an issue in mine until I put the flat bottom on and totally enclosed the engine bay, without the flat bottom it never got very hot on the interior

[NiceGuyEddie]

My headers are within 1/2" of the footwell. I have one layer of Fatmat plus boat carpet and there is absolutely no heat in the foot well due to the headers. You can touch the carpet and it's always "room temperature" or whatever is ambient.

I have the FFR Vintage Air heater (circa 2004) and warm engine air "naturally" flows through it and that's the source of extra heat in my footwell. The the footwells are sealed well with pool noodles.

In the warmer months I put one of those turkey oven bags over the heater blower that's on the firewall side. It doesn't look pretty but it works.

[Fman]

Ted this is probably subjective to each owner, I also drive in shorts during the warmer months... for me without the header wrap, sticky heat shield, bilge fans, and insulation I stuffed in the door jamb gaps it was more heat than I wanted coming at my legs and into the cockpit. I just went out for a drive today it was 55 degrees out, footbox heat not even an issue. On an 85 degree day this is a totally different scenario (at least in my car). I did use the Coolmat insulation on every panel in the car including the trunk along with sealing off all gaps I could find in the footbox. It is only .040 gauge alum panels separating a 450-500 degree header that is 1/2" from the drivers footbox. Conductive/Radiant heat is impossible to avoid with this scenario. My wife says the passenger footbox feels fine but the header is much further away from the footbox in comparison to drivers side. I also have a 500+ HP 427 could totally be different with a 302 or smaller engine. When you ask this question make sure you are comparing apples to apples (ie: 427 to a 427). Kind of like Gas' n touring pipes sound WAY different on a 302 compared to a 427 (I installed a pair on a 302 so I heard it with my own ears).

Ted, if I was going to do it over I would do the coolmat AND do the lizard skin spray over it so you have double heat barrier. This is just my opinion and experience.

[GWL]

If you decide to use stand off heat shields/panels think about using mirrored stainless steel. Stainless steel is one of the lowest conductors of heat of all the metals. In addition, the mirrored surface will reflect radiant heat away from that panel.

I used .050" mirrored stainless on my foot boxes and firewall. Besides being functional they look good in the engine compartment.

George