Exhaust heat shields

[Joel Heinke]

I have a situation where the headers run very close to key engine and transaxle components and also close to the firewall (thus the driver/passenger seating areas).

I'd like to build in some heat management provisions and am hoping there are some who've "been there, done that".

The headers are made from 304 SS in .063 wall thickness. I do plan to have the headers covered with a ceramic coating which will help but I'm fairly certain won't be enough in and of itself. I'm reluctant to use traditional header wrap as it's not really a "permanent" solution and I don't really like the look of it.

In doing some searching, I found this: Heatshield Armor

Does anyone have firsthand experience with this or a similar product? Does it work well? Are there other heatshield approaches/products that work better?

The firewall is 1/4" thick aluminum and I'm sure will be a very good conductor of heat. The front header is located about 4" from the firewall. What heat shielding approaches work best on a firewall? One thought I had was to use this same Heatshield Armor material and blanket the firewall with it. Are there better approaches?

Please provide your experience on what's worked best to keep the heat out of unwanted places.

 

[Neil]

A gold reflective film makes an effective barrier for radiated heat. Gold reflects infrared wavelengths more effectively than any other material. Here is one possibility:

https://www.amazon.com/Design-Engineering-010394-High-Temperature-Reflective/dp/B0039Z5TUY?th=1

Whether this is real gold or just a gold-colored film is not clear but it might be worth trying. They sell it in 2' x 2' sheets as well as tape.

 

[Ian Anderson]

Joel
Are you getting them coated inside and out or just sprayed on the outside?
The two layers in and out work a lot better.

Ian

 

[Joel Heinke]

Joel
Are you getting them coated inside and out or just sprayed on the outside?
The two layers in and out work a lot better.

Ian

I will certainly try to get the coating done inside and out. I cleaned the insides with rubbing alcohol prior to welding the headers in preparation for having the insides coated.

 

[Joel Heinke]

A gold reflective film makes an effective barrier for radiated heat. Gold reflects infrared wavelengths more effectively than any other material. Here is one possibility:

https://www.amazon.com/Design-Engineering-010394-High-Temperature-Reflective/dp/B0039Z5TUY?th=1

Whether this is real gold or just a gold-colored film is not clear but it might be worth trying. They sell it in 2' x 2' sheets as well as tape.

So it sounds like this gold heat screen is made for keeping radiated heat out but not for keeping it in. In other words, not for direct use on the headers as it's heat rating is way below the heat from a header primary. So it might be part of the solution but not all of it. For example, for use on the firewall to keep heat out.

At $100 for a 2' by 2' sheet, it doesn't come cheap. They claim a 36% heat reduction in a "heat flux test" (not sure what type test that is). I think I'll need more than 36% heat reduction or I'll have "heated seats" even in the summer time. So again, probably part of the solution but I'd be best served to have other heat management stuff in place to keep the engine bay temps down.

Thanks for the tip/lead Neil!

 

[Joel Heinke]

So now that I have the front side header complete, I put the engine back in the chassis so I can fabricate the secondary pipes. Here's the clearance between firewall and header.

At the closest point, it's only a 2 1/2" gap and the seat backs are right up against the other side of that firewall. Oh, and gas tank runs down the center of the chassis so the back end of it is also right up against the firewall. Thus, that's why I'm seeking out best practices for heat management.

 

[Davidmgbv8]

I have not used this however I know several who have, one in a Europa. They say it works well and can be painted or sprayed. Made here in Houston but can be obtained thru Eastwood, Speedway, ect.

LizardSkin

Automotive Heat and Sound Damping

lizardskin.com

 

[Terry Oxandale]

Tough situation. As much heat as gets input into a normal longitudinal setup on the firewall, I can't imagine the amount of radiant heat pushed to the aluminum firewall panel. You may have to go with something more elaborate (multiple panel using an air gap with force air in between the panels, along with whatever thermal protection you use) to make this livable for any extended length of time (30 minutes or more).

 

[Ian Anderson]

Joel, in my GT40 when I got stuck in traffic my firewall got too hot to hold my hand on for any period f time.

I fitted two of these to blow air rearwards under the rear clip and if I was in traffic and the temp rose, I could turn these on manually and within a couple of minutes the firewall heat dropped considerably.
Something like https://www.ebay.co.uk/itm/ABS-12V-...D3m8V4eYG8L1TGhJuO57QyEB5FEQ7fMYaAsL1EALw_wcB

the airflow will help considerably

Ian

 

[Howard Jones]

My advice would be to ventilate the area with ambient air with a floor with holes in it and directed scoops in the bodywork along with ventilated rear deck cover. In your case, you have a body type to try and keep correct but you will need airflow through the engine room one way or another. I have tried just about everything to cool the engine room in my SLC and if you just try to shield the stuff you want to keep cool while pretty much keeping all the generated heat in the engine room just about anything will heat soak in less than a 1/2 hour (full power race track pace).

As it turns out ceramic coating really is the one way to get the heat out of the car and not need to shield everything from it after the fact. Then this stuff on the firewall and then point shielding things like fuel pumps etc.

Pay special attention to shifter cables. Three or four layers inside a reflective cover are what it has taken to keep them alive in my SLC for shifter and throttle cables.

Aluminized Heat Barrier, Adhesive Backed - Pegasus Auto Racing Supplies

Our Adhesive Backed Aluminized Heat Barrier Cloth protects sensitive components from heat. The reflective surface withstands radiant temperatures of 2000F.

www.pegasusautoracing.com

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[Joel Heinke]

The Miura bodywork has a couple of provisions for getting fresh air in and out of the motor room.

For bringing air in, there's these vents at the rear of side windows, although I'm not sure how effective they really will be.

And to get hot air out, what looks to be a rear window, is really just a set of louvres open to the outside. My guess is that these openings will be effective in letting hot air out.

My biggest concern is heat management for the "hot spots" within the motor room.

 

[Terry Oxandale]

Inserting/fabricating some vanes, from the side window vents, into an air-gap panel in front of the header, should help. The vains could ensure good distribution of air flow to where you want it, and then let it flow on out of the rear "window". Gonna have to treat your firewall like a brake rotor on the cooling sounds like.

 

[Randy V]

On top of gold foil for the reflective insulation properties, could you implement a couple of 10” Spal fans to move air out the bottom of the car toward the rear also?

 

[Cliff Beer]

Ditto what's already been said here: coat the headers with ceramic, and also use some fans to move air out of the compact area between the headers and firewall.

I have similar cooling issues in my project car. In addition to ceramic coating the headers I installed two 10" Spal fans, one at either end of the headers to move air around. There's also two more 10" Spal fans to move hot air out of the engine bay. Sounds a bit busy with four fans running, but it certainly works to dramatically reduce temperatures.

And, of course, some good surface insulation on the firewall should help too. Between these three things I would think the firewall temp should be managed and not present a safety issue with the proximity of the fuel tank.

 

[Joel Heinke]

Thanks for all the replies and information. I do think some strategically placed fans and ducting will be the way to go for keeping firewall temps under control. Now I'll need to make sure the alternator is up to powering these motor room fans in addition to the radiator fan, electric water pump, EFI fuel pump, etc.

I hadn't seen any replies about the Heatshield Armor product I asked about in the first post. No wonder, the link in my first post doesn't work so of course no one could comment on it. Ok, here's a link that works: Heatshield Armor

Their claim, "Armor™ Series exhaust heat shields can stop up to 70 percent of radiant heat from the exhaust pipes and components." That claim sounds great but does it really work and are there any cons to the product? Does anyone have firsthand experience with this product?

 

[Terry Oxandale]

I use this to protect the overlying fiberglass (about 3" above the header tubes), and I cannot confirm a 70% reduction, but it did prevent damage to the glasswork and paint. I also used it on several 1mm aluminum shields I fabricated and placed at various points in the engine bay to reduce radiant from the headers to the oil coolers, seat-back, around the coolant tubes going forward to the radiator, etc. The main reason for most of this was to reduce heat-soak on the fuel system. I recirculate the fuel, and after 30 minutes or more on the road, on a hot summer day, the tank's fuel temperature approached 165 degrees F, which started causing vapor lock issues. In your case, you've got heat more directly on the tank right off the bat. Lastly I opened up the side scoops, making them fully functional and ducted through a fuel cooler on one side, and general forced air on the other side to help push air through the engine bay. I no longer have the heating issues, but it was a lot of work to accomplish that.