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Modern material for making new interior firewall insulator?

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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!

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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

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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.

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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.

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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.

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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

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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 by FastWoman

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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.

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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.

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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.

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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.

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Have you seen the reproduction firewall insulators that Classic Datsun Mortorsports offers. Depending on the degree of originality you are looking for, for $140, it looks pretty original, has insulation backing, and all of the correct cutouts. Don't know what the material is but may be worth checking out.

Dan

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I think I found something: Garage Guard by Oil-Dri at Pepboys. It is pretty tough rubbery material with one fuzzy material side and one black rubber side which is close in appearance to the original 240z part's rubbery side. I should be able to glue a thin backing on it to strengthen it.... maybe even clean up the old and glue the two together.

There was also a foam anti-fatigue mat that would work but it was light gray and I would not want to paint it.

240dkw Dan, I'll also look for the art board material. Sounds like it may work well with the rubber.

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Mjr45 sorry for the delay in getting back. I would NOT use the foam carpet padding. I agree with you that it would crumble after a while. The other type of padding looks like old string,fabric and other stuff amalgamated together. This stuff is somewhat fire resistant but not fireproof.

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Just a photo update. Flew the template copied from the saggy ripped-up original 1000km and installed. Many holes were way off the mark or not suitable in shape or size. Re cut and drew centres to fit....now to make "Mark I"

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Now that I have more accurate measurements, I am making two variants of the firewall insulation panel:

1. Foam board (as per Dan's excellent recommendation above; BIG THANKS DAN!) with the jute-backed oil-proof fabric glued to the front.

2. High density foam with the jute-backed oil-proof fabric glued to the front.

I think both will work well. The foam board is firmer and fits well (when I tested the template), however the high density foam seems closer in thickness compared to the original and it will soundproof and insulate better.

I also sourced correct size nickle snaps that I will secure with ss hardware to replicate the floor mat snaps on the original.

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Here is the freshly cut foam board being glued to the fabric that is very similar to the original.

There is a small square of the high density foam being test glued on the upper right to see if the glue eats it.

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Here is the original template and the high density foam cut out along with scraps.

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First one off the line using foam board:

Replicated:

Notes: 1. Fasteners to be installed next week. 2. Smaller hole sizes in more accurate locations were used to improve insulating & sound proofing.

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Original:

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Edited by Blue

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The HD Foam seems to be the ticket. THANKS JIM!

The rubber outer surface and the high density foam backing bonded very well (better than the foam board). IFor the record, I used Loctite Spray Adhesive 200.

The flexibility of this combination seems to be very much like the original. I'll put a layer of foil on the back as per Jim's suggestion.

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Here is a detail of how well the outer rubber/fuzzy layer has bonded to the grey foam.

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FWIW I've used a hot glue gun to attach the foil bubble wrap to the insides of engine compartments, bottoms of hoods, etc.

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