65 Inside Dash Insulation

[kevinshi]

I found this flush up against in the “ceiling” of my dash behind my instrument panel – 1" thick fiberglass insulation. I also have remnants of jute insulation in the *middle* on the dash ceiling (above the firewall). Finally, I believe I saw similar fiberglass insulation in a 1965 sedan in the dash ceiling above the glove box.

I am now trying to decide how to "restore" all this in my car...

I have searched here on Comet Central and am only able to find a couple of mentions in passing. Also, after much Googling I’m not finding anything meaningful – certainly not any replacement insulation ‘parts’ and the like. (If there is a more complete thread on the site here I apologize for not finding it before this post.)

Questions:

1. 1) What was the original installation of insulation above the firewall? (Am I correct that it was exclusively on the ceiling of the dash and a combination of jute in the middle and fiberglass on the “ends” of the dash ceiling?)

• 2) Why did Ford put insulation there? (I am guessing it was temperature regulation for the windshield – e.g. to help the defroster be more effective? Or perhaps anti-rattle?).

• 3) Are there replacement parts out there I have just failed to find (which is presumably just trimmed fiberglass insulation)?

• 4) If I cut my own insulation what material is considered best practice (stick with fiberglass, use modern closed cell foam board, cotton jute, aluminum backed jute, self adhesive dynaliner, etc.)?

• 5) Anyone have any idea the “weight” the original fiberglass (mine is very heavy considering it is only 1 inch thick)? The best facsimile I can come up with so far is this which I think would work - it's 1" thick but may not be as dense as the original.

Many thanks in advance!

[poboyjo65]

Yea Mine had it. I was glad to get rid of it & the years of dust built up in it. I didn't insulate my firewall very well,,I'm getting a lot of engine heat in the cabin, so I'm going back in with the generic dynamat stuff from summit for starters,may add to it with the stock type piece .as far as the top or bottom of the cowl I guess I 'll put it on there too. but no fiberglass for me!!

[kevinshi]

Yea I don't think what Ford did here was about engine heat - it doesn't really sit between you and the engine. I think there is something else going on here...

Did yours have the insulation on the glovebox side as well? Did it have any insulation in the middle (also on the ceiling of the dash) - if so do you remember what it was made of?

Also a terminology lesson would be very welcome - what exactly is a cowl (yes, I am that much of a noob...).

Thanks,
kevin

[poboyjo65]

cowl is between the hood & windshield, where the vent slots are. it is a chamber all way across ,& where your heater pulls it's air from as well as fresh air vents. so the insul. is probably there for sound as much as outside temp. yes mine had it all way across & on bottom of the cowl ,,(what you called the ceiling I think) it was like a fiberglass type stuff best I recall. ( a dust motel )

[comethead]

I agree with Johnnie that the stuff was sound deadener. I’ve taken apart Mustangs of the era that didn’t have it. Mercury’s being higher-end had it.
I was glad to take mine out too. Didn’t replace it either.

Joe

[kevinshi]

Sound deadening makes sense to me. Thanks for the definition of cowl.

See below pic for where I found this originally (I just reinstalled the thing so I could take this picture ).

...yes mine had it all way across & on bottom of the cowl

Just to make sure I understand what you mean by "bottom of the cowl" - in the below picture that would include the the rusty area (ahem) seen behind/below the insulation (on the left and then obscured toward the right by my wiring), correct?

[poboyjo65]

I was wrong.You were right, it's on the bottom of the dash too. I had forgot about that. I remember thinking it was odd. Maybe it is too keep the sun from getting the dash too hot as well as for noise. I guess I should put some of the dynamat under my dash too.
here is a pic of the bottom of the cowl & bare heater duct. I was thinking it had some insulation on it too. another hole on driver side for fresh air.

[kevinshi]

Do you recall whether the bottom of dash fiberglass insulation you removed extended all the way across the dash (over to above the glove compartment)? I *think* it may have only been on the two ends of the dash and not in the middle (which woudl make sense given the speaker and grill are in the middle... (duh)).

Further I speculate that they did put jute insulation on the bottom of the cowl - aka the surface between the firewall pad and the dash fiberglass insulation (aka "above" the firewall pad and "behind/below" the fiberglass dash insulation). Agreed?

(Taking your "dust motel" comment to heart I think I am still likely to try and replace all of this under the theory (ahem) that the Ford engineers put it all there originally for a (somewhat good) reason.)

Two tangential questions (sorry to be a bit off topic):

1. 1) In your picture - what is that pink colored material in the heater fan hole on your firewall? I don't have any material there... I think I might be missing a gasket or a seal or something. And what I have is definitely NOT pink.

• 2) Opinions on how much I should worry about surface rust I am seeing on the bottom of my dash and cowl (as per the picture above)? My rust is extensive but it is all surface - not even remotely pitting. Based on my situation I have two choices. (a) Leave it alone (it is just surface, nothing really all that serious). (b) Paint POR 15 up there. Option (b) will be a pain in the butt - I must brush paint - I can't spray (long story)... thus I'm probably going to have the paint dripping on me while I'm lying there on the floor pan. Augh, I dread dealing with this. Please tell me to stop being a baby so I have the energy to do the work.

[poboyjo65]

That pink thing is a filter from a respirator it was the perfect size to fill the hole to keep overspray out of my engine bay. There is a thick foam seal that goes around the heater blower motor that goes in that hole. if you redo your heater box with a new foam seal kit it will come with one or you can buy it separate from any mustang parts vendor.

you could glue a plastic skin on the fiberglass insulation,,, it should keep dirt out. Yes it was most likely not around the speaker hole. another thing that comes to mind is sweat,,,condensation. cold metal getting sunlight= sweat. this insulation probably helps with that as well as sound & temp. sweat is most likely where the surface rust comes from.

my cowl had some leaks around the air ducts on the sides with some pretty heavy rust so I sanded it kinda smooth, & sanded the surface rust in the center also. I put POR15 on the heavy rust ,& the bare metal I hit with the green etching primer.
jute does sound familiar for the cowl , I think I remember sanding the remnants of it off. seems like it was glued on pretty good & left pieces stuck to the cowl. I guess you could leave the surface rust but I wanted to be able to glue something back on & was thinking it might not stick to the rust, so even if you dont coat it you might want to knock off the loose rust so glue will stick. I think I got in a hurry & did a poor job of insulating even though I prepped for it . I think I was thinking I could do it when I put in new carpet. I just got to anxious to drive it