Sound and heat insulation question on firewall

[TXJosh]

Hello to all

I am building a mkiv complete it and am just now beginning the installation of my FFMetal firewall forward.
I intend to have a heater, maybe a glove box.

In general, is it well advised to use sound/heat insulation on the inside (dash side) of the firewall?
What type of insulation? I plan on using lizard skin for the interior panels as a whole, but am leaning towards a butyl adhesive on the firewall such as second skin. I will use shark hide on the engine side.

What is the best sequence for placing on the installation? I’d like to cut the heater template and install the insulation early, and then cleco the firewall in place. Is it difficult to cut through the insulation when installling the rest of the behind-dash components later on?

Appreciate your thoughts. Many great build threads on this, but appreciate the current view.

[gbranham]

I used Thermo-Tec for interior side of all my aluminum panels, including the firewall. It's easy to cut and puncture if you need to cut it or make holes in it after it's installed.

[Dgc333]

I am building a 33 and ordered it with the sound & heat insulation kit. The firewall and tranny tunnel are covered with a dynamat like material then there is a 1/2" thick thermal/acoustic foam that goes over the dynamat material. The floor, sides below the doors, back wall and inside the doors just gets the dynamat only material.

[FLPBFoot]

Firewall forward, heater, and glove box on both my builds and used Dynamat on the inside of the firewall. Used Breeze Koolmat on everything else. All works great.

[ggunter]

I did not put any insulation on my firewall and thought it was a mistake, but after the car was done, and on a hot day I put my hand on the inside of the firewall while driving and found it only warm. Insulation there would help but not mandatory.

[TXJosh]

Firewall forward, heater, and glove box on both my builds and used Dynamat on the inside of the firewall. Used Breeze Koolmat on everything else. All works great.


And what sequence did you use? Did you all outfit the firewall and then place insulation around the components or did you insulate the whole firewall and then just cut and drill through it as necessary?

Can you river through the insulation?

[rthomas98]

And what sequence did you use? Did you all outfit the firewall and then place insulation around the components or did you insulate the whole firewall and then just cut and drill through it as necessary?

Can you river through the insulation?

I used kilmat for mine (similar to Thermotec). But I laid it down first and then drilled the needed holes through it. The stuff is really easy to work with. If I was to do it again I would of drilled everything then mounted. The mat tends to gum up the drill bits and hole saws. But either way works.

[edwardb]

I've done multiple builds and have always only insulated on the inside. I've used a variety of products including Lizard Skin, Dynamat, and Second Skin. That plus carpet where it's used. I've never had a heat penetration issue from the engine, headers, whatever. I see lots of people putting insulation on the firewall and engine side of the footbox. I just haven't found it's necessary. Pay particular attention to make sure everything is sealed up. Even the slightest hot air from the engine will feel like you left the heater on.

As far as sequence, I have found some of the hard to reach areas like the firewall and footbox pieces are easier to cover before assembly. Also, for spraying lizard skin, easier to do before installing things like the pedal box, wiring harness, etc. The rest I do after assembly. Lots of pictures in my build threads linked below FWIW.

[dbo_texas]

I laid out all my hardware and did the cutouts (heater, grommets, etc), then used a roll of brown art paper to cut some templates for each section I would end up covering with Termotech CoolIT sound/heat barrier. I just traced the template onto the CoolIT, then cut it with a razor. Make sure to leave 3/4" at the top for the bulb seal. Peel the backing and then stick into place. All was done after firewall was riveted in place (see pic - ignore the yellow arrows - those were my under dash courtesy light LED locations). I've only done the PS footbox (same way, making paper templates for each section) and it went pretty quick. I'll do the entire interior this way.

https://thefactoryfiveforum.com/attachment.php?attachmentid=190761&d=1696256810

[nashuanuke]

I used fatmat, and did the firewall before messing with electrical just so it's there to work around and drill out as necessary.