Modern material for making new interior firewall insulator?

[240260280z]

I have the moldy, torn, original Jan 71 240z firewall insulator that I wish to transcribe to a new material. Can anyone recommend a material to use?

I plan to put peel-and-seal on the fire wall along with bubble foil for sound deadening and thermal insulation so the new material does not have to insulate.

Maybe even just a semi-hard material to replicate the carboard/masonite part of the insulator will suffice.

I need some ideas before I hit the material/fabric/building supply stores

Thanks as always!

[jfa.series1]

Look at the trade-offs of purchasing a new OE-type insulator pad vs. making one up yourself. The OE product has pretty high density plus all the correct cutouts for all the mounting points and thru-wall connections. A couple of cautions on bubble-foil: it will break down over time and it will easily crush anywhere a light pressure is applied.

If you want to go the insulated foil route, look into closed-cell polyethylene foam with foil backing available in 1/4" thickness. It does not crush or breakdown, has a good R-factor and decibel reduction factor. I used this on the entire floorpan of my car AND the firewall before putting my original firewall pad back in - it was still in very good shape. I can provide a link for the foil if you have an interest.

For a DIY pad, consider 1/2" high-density foam sheeting from a hobby or upholstery shop sandwiched between a foil coating. Or possibly 2-3 layers of the poly-foil I mentioned above glued together with a spray adhesive.

Jim

[FastWoman]

Blue, a combination of masonite and foam sounds like possibly an excellent design strategy, acoustically speaking. Do you have any photographs of the original insulator? Maybe just a conceptual drawing. I've never seen one. I don't think I even saw the one on my '75 that I owned back in the 80's.

Have you considered aluminum for the hard material? Maybe bond insulating material to the aluminum with polyurethane foam -- e.g. "Great Stuff". If that's not strong enough, Gorilla Glue is just a denser formulation of polyurethane foam.

If the assembly produces a very dead-sounding "thunk" when you hit it with your knuckles, then you've got a good design.

[240260280z]

Ideally a rubbery plastic material will be great. Something that is black or can be painted.

[FastWoman]

How about covering your insulating material with a thick layer of pickup truck bed liner?

[FastWoman]

Blue, thanks for the graphic! What I'm wanting to know is how the layers are put together. Is it a masonite panel against the firewall, with insulation on top of it? Or is it flipped the other way around?

The masonite could serve as a dense, acoustically dead sound reflecting layer. Some of the best acoustic materials use rigid, mass-loaded panels, alternated with soft, sound-absorbing panels. For instance, I believe Lexus was experimenting with body skins made of layers of aluminum sandwiching a thin layer of balsa wood.

[240260280z]

The outer black layer is a thick rubbery-paper-like material. Sort of like an asphalt roofing shingle. The back is that horse-hair/jute stuff.

[240dkw]

Blue: I would try looking at a Art store for the display boards that are used for things like science fairs. I use it for templates when I am doing a woodworking project. It is high density foam, tough and comes in black.

Dan

[FastWoman]

Ah, OK, now I'm getting it. I thought you were talking about an insulator on the ENGINE side of the firewall. :embarrass:

I know this sounds goofy, but how about layering up some roofing felt and quilting material -- maybe 4 or 5 layers, alternating between the two materials? That would create lots of transitions between high and low acoustic impedance. Each layer of felt would knock quite a few dB out of the sound, and the quilting material would prevent direct physical transfer of vibrations from one layer to the next, AND it would insulate a bit. Bind it all together around all the edges by punching holes and hand-stitching. I don't know whether that would be stiff enough, but I think it would provide you lots of acoustic and thermal insulation.

If you need more stiffness, find a place where workmen are doing vinyl siding, with aluminum wrapping. You might be able to pick up some scrap aluminum.

Edited August 3, 2011 by FastWoman

[mjr45]

When I took the insulator out of my Z, it basically crumbled apart, so I'm trying 2-3 layers of Dynamat to see it that will work, the problem is getting it up behind the heater over the tranny tunnel plus all the cutouts.

[240260280z]

I am fortunate and have everything out of the car. I just need to make a new one.

I tried to order one from VB/BD yesterday but no availability.

[tlorber]

I've been using carpet padding to replace the jute inside the car. I also backed the hard plastic interior panels with it to reduce noise and heat transfer.