C3 Dash Insulation and Heater Box Install

[Jack O.]

Hi everyone,

I'm working on a 69 with air. Purchased a repro dash insulation mat that was very expensive and fits horribly. From what I've read on this forum, from what's left of my original, and from the AIM, it appears this dash insulation goes between the heater box and firewall providing the seal, correct? I also got a heater box rebuild kit that comes with foam for that area but from what I read that is for use on the engine side of the firewall?

Just want to be sure because my issue is trying to get the upper left heater box stud through the firewall far enough to get a nut on it. I believe it's because the dash insulation is is too thick (in general it's a piece of crap). I've had to cut this thing so much it barely covers more than what was left of my original. If the heater box was sealed only with this foam from the heater box rebuild kit there would be no problem with how far the stud protrudes through the firewall.

Thanks,

Jack

[Jack O.]

Re: C3 Dash Insulation and Heater Box Install

I can compress the insulation mat so it maybe takes up an 1/8". Just not much play based on the length of the stud attached to the heater box which I'm sure is original. I can definitely see that the original mat went around the bottom but not much left of the top of the original mat to tell if it fit under the heater box as well. I'm probably just going to remove most of the insulation material from the mat where it fits under the heater box and be done with it.

[Keith M.]

Re: C3 Dash Insulation and Heater Box Install

Very interested in this as I will be doing this job on my 69 in the near future. Mind sharing where you got your insulation kit?? I just bought one. PM if you prefer not to post source here..though I think it perfectly fine if you did.

As for fit..I do not know what original design was. I would fathom insulation would not go between heater box and firewall as that would not be a tight seal.

[Jack O.]

Re: C3 Dash Insulation and Heater Box Install

There are several places that sell the dash insulation mat and from what I can tell it's the same one. Other than general fit issues the biggest issue is that the backing is made from thick vinyl material that's not very flexible. From my research here on the forum I think Dr. Rebuild used to make, or at least sell, one that was far superior but I did not see it listed any longer.

I'm certain the lower part of my original insulation went under the heater box and would therefore conclude that the entire thing did as well. Also, the AIM has you cut and enlarge a section of it around the heater box for C60 since the firewall opening is larger for C60. The repro mat has this area (as well as another C60 related area) perforated for easier removal. Once cut it fits perfectly around the opening although, as I said, seems to thick to get original length fasteners started.

[Keith M.]

Re: C3 Dash Insulation and Heater Box Install

Jack,
What is your car? I have a 69 L46 and think the product I have is different than what you describe. Here is what I got from Paragon https://www.paragoncorvette.com/prod...d-deadener-kit

Can you share what product you got?

Keith

keith

[Jack O.]

Re: C3 Dash Insulation and Heater Box Install

69 L69 with A/C. Your link is the stuff that goes right up under the upper dash. That worked fine for me. Here's what I'm talking about https://www.keenparts.com/corvette-p...partnum=290029. Looks the same as what CC and others sell too but many were out-of-stock. There are many others sold (Hushmat) but I was looking for something similar to factory as opposed to a general insulation.

[Keith M.]

Re: C3 Dash Insulation and Heater Box Install

69 L69 with A/C. Your link is the stuff that goes right up under the upper dash. That worked fine for me. Here's what I'm talking about https://www.keenparts.com/corvette-p...partnum=290029. Looks the same as what CC and others sell too but many were out-of-stock. There are many others sold (Hushmat) but I was looking for something similar to factory as opposed to a general insulation.

ahh. now i get it. Turns out I need all that insulation too. As an engineer I find it hard to believe that design called for any of it to be between the heater box and the firewall. But I do not know for sure. Maybe someone with a survivor could confirm one way or other. As of now my intent would be to not have any firewall insulation between box and firewall...whenever I get to that.

[Kenneth K.]

Re: C3 Dash Insulation and Heater Box Install

Hey everyone -

Does anyone have a recommendation for a supplier for a 69 firewall insulation that is correct and actually fits? I bought one from CC and the four holes for the heater box do not align up- not even close. See pics. I placed the heater box gasket on the box and as you can see it fits perfectly. Using the gasket as a template I placed in on the firewall insulation. As you can see it fits horribly.

Other suppliers I looked at have replacement firewall insulation that from the pictures appear to only cover about 1/2 of the firewall. CC said I could send it back or just cut new holes for the 4 studs. I am reluctant to cut new holes because the rest of the insulation may not fit and it looks like I would have to trim a lot of material around the heater box. Any recommendations?

Thanks
Ken

[Jack O.]

Re: C3 Dash Insulation and Heater Box Install

When I checked about a year ago and it seemed all vendors were providing same thing. I have an A/C car and the heater box fit fine but I had to do some serious cutting on it on the driver's side. From what I've read in other posts Dr. Rebuild use to offer a better one.

[Kenneth K.]

Re: C3 Dash Insulation and Heater Box Install

I figured out that the firewall insulation I purchased from CC is made by a company called QuietRide solutions. I am pretty sure this is the manufacturer of all the firewall insulations for 53-2010 that are sourced by all the other corvette suppliers.

I saw a note on the QuietRide website (QuietRide.com) that a 1969 insulation may have holes that appear to be from a 1968 or a 1970 -1972 production depending on when the car was built and if you run into these issues to call them. That sounded like my problem so I called their tech line and spoke with a gentleman named Gary. I sent him some pictures and dimensions of my heater box. Since my car was build August 28 he said it has a 1970 firewall rather than a 1969. He sent me the correct firewall and it fits perfectly. If you’re looking for a correct reproduction I highly recommend sourcing it directly from QuietRides. They really know what they are doing.

Attached is a side-by-side photo that’s shows both the 69 and the 70 firewall. The top one is the 69. The 70 has the cutouts for the heater tubes. The differences are obvious. I could have poked new holes and trimmed a lot of the 69 insulation to make it fit as CC suggested but it would not have been correct. If you need to replace your 69 firewall and don't know if you have a 68, 69 or 70 heater box I would talk to Gary and he will make sure you get the correct one.

[Michael L.]

Re: C3 Dash Insulation and Heater Box Install

When I installed my padding I had a couple of the rubber attachment plugs that I could not get to reach through the firewall no matter how hard I tried. There were enough plugs that did fit and the padding was well secured by those and other dash components so for those select plugs that didn't reach I put a plug through the fire wall prior to attaching the padding and then put a plug through the padding so that it looks like the plug is perfectly installed. Just my little life hack that saved me a bunch of struggling.

Mike

[Keith M.]

Re: C3 Dash Insulation and Heater Box Install

I figured out that the firewall insulation I purchased from CC is made by a company called QuietRide solutions. I am pretty sure this is the manufacturer of all the firewall insulations for 53-2010 that are sourced by all the other corvette suppliers.

I saw a note on the QuietRide website (QuietRide.com) that a 1969 insulation may have holes that appear to be from a 1968 or a 1970 -1972 production depending on when the car was built and if you run into these issues to call them. That sounded like my problem so I called their tech line and spoke with a gentleman named Gary. I sent him some pictures and dimensions of my heater box. Since my car was build August 28 he said it has a 1970 firewall rather than a 1969. He sent me the correct firewall and it fits perfectly. If you’re looking for a correct reproduction I highly recommend sourcing it directly from QuietRides. They really know what they are doing.

Attached is a side-by-side photo that’s shows both the 69 and the 70 firewall. The top one is the 69. The 70 has the cutouts for the heater tubes. The differences are obvious. I could have poked new holes and trimmed a lot of the 69 insulation to make it fit as CC suggested but it would not have been correct. If you need to replace your 69 firewall and don't know if you have a 68, 69 or 70 heater box I would talk to Gary and he will make sure you get the correct one.

Kenneth,
If I could I would PayPal you a beer for this post! Like you I have a late(r) 69 build being late October. So I need the heater core cutouts like you show in the lower insulation. I did post previously above. I have not gotten to installing the (incorrect) one I got from Zip but was happy to learn I got it last August so still returnable. I also checked the template of the heater box studs and they do not line up with the Zip insulation. Gonna place a call to Quietride...probably next week. I need one similar to yours but without the AC cutout near the center top. Thank you so kindly for this very valuable (to me) followup.

[Kenneth K.]

Re: C3 Dash Insulation and Heater Box Install

Michael- My original plugs are still in the fiberglass and I would like to remove them so I can reuse them with the new firewall insulation. Do you have any tips on how to remove original plugs without damaging them?

Keith - yep I bet you have a 70 heater box in your late 69. Call Gary at 209-942-4777.

[Keith M.]

Re: C3 Dash Insulation and Heater Box Install

So I finally got around to calling Gary today. From what I can tell I need the cutouts for the heater core tubes. There are remnants of the original firewall insulation and there does not appear to be the rectangular cutout at the top center. And interestingly there does not appear to be heater core tube cutouts and pretty much looks like the insulation was fit AROUND the heater box.