I have a '37 LaSalle opera coupe and note a new firewall insulator is about $325. They say it is made from ABS plastic with insulation. Seems to me I could buy a sheet of approximately 1/8th" ABS cut and heat gun my own firewall cover, and put insulation on the back-side. Thus looking for suggestions. I have the old insulator which appears to be made of Masonite and a jute style backing, so I already have a great pattern. I'm concerned about interior appearance of course as one can see a goodly portion of the firewall from inside. Not sure what type of ABS plastic to buy and have no knowledge of the stuff and my initial internet search seems to show it is available in many thicknesses. As far as insulation/sound deadening material goes, there are so many choices available today for interior insulation it's hard to decide. Pricing on the stuff also seems pretty high so seeking advice from those of you who have been there and done it. I want to cover the floor and possibly the inside of the doors. The original 'insulation' is still in the car and it looks all the world like tar-paper. The vehicle is now powered by a '76 Eldorado 500" engine and is in final stages of the build. Here's a before photo. I drove this thing through college and just got it back. Here's a photo of the intake (Bulldog) I've smoothed and now powder coated.
Carl, On my COE I used grey sound board and jute on the firewall insulator pad. For the back of the cab, I used 1/16" ABS with insulation. I can't find photos of the firewall pad, but here is the back of the cab. Good to see you got it back !
That insulation that looks like tar paper probably is. I know Ford used tar paper, asphalt saturated roofing felt actually is what it is, until at least the 1970's in some cars. I had a 1974 Maverick, that's what the trunk divider was, a sheet of regular 50lb roofing felt, or tar paper if you prefer. You could still see the nail lines painted on it! It was also used on inner quarter panels and floors as well.
Very nice installation..I wasn't thinking about 1/16th stuff until I see what you have done. I can probably use some of it in the interior. Thanks
You can buy expanded pvc foam sheet in 1/8" x 4 x 8 sheets at your local plastics distributor. Cut it using a box cutter knife and straight edge. Using a heat gun and a straight edge, you can bend and form it into almost any shape. Once cool, it will stay put. Then, I would use DEI's Under Carpet Lite (https://www.designengineering.com/under-carpet-lite-sound-absorption-insulation-70-by-linear-foot/. Buy their spray glue. It works well.
If you have an art supply store in your area they sometimes carry large panels made of various materials, you may find something that will work. Sign shops use a product called Coroplast (it's what that political campaign signs people stick in their yards is made from) - that's another possibility.
When I put the SBC in my Austin gasser I knew heat would be an issue inside the cabin. So I used foil backed self adhesive foam directly on the inside firewall. Then I built standoffs that were 1" tall, and made an inside removable firewall cover from 3/8" plywood. I covered the backside of that with more foil backed foam, and then carpet on the opposite side. It attaches with screws, and I have access to wiring behind it if I ever needed it. My interior stays cool in all sorts of hot weather, and even without AC my car isn't getting any engine heat transferred.
Tape up your old insulator, lay up a couple layers of glass & mat, trim the edges, pull off the old insulator, stick some new insulation on the firewall side, and glue naugahyde on the interior side. Did something similar in the past; worked good.
I love using 1/8" ABS for interior panels, making panels to finish off a trunk, etc. It heats and bends easily, keeps it's shape and is waterproof. For insulation, there is an insulation that is a bit hard to find, but looks like black vinyl or leather. That would be perfect for a visible firewall, over the ABS! I used some on the 61 Olds I did, for underhood insulation.
I used a 1/2 inch thick acoustic foam with high temp foil face and adhesive backing. It worked extremely well on the firewall of my 39. Got it from amazon and it was pretty cheap. here is a link to it. https://www.amazon.com/dp/B072WHC63F?psc=1&ref=ppx_yo2_dt_b_product_details