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!

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

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.

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

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

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.

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.

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

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, 201113 yr by FastWoman

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.

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.

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.

tlorber, did you use foam carpet padding? I'm looking for padding to put under all the carpet

on top of the Dynamat and not sure how well foam will hold up.