Firewall Insulation

Back in 2013 when I redid the car’s interior I ordered an insulation kit from a company called Quiet Ride. The kit was quite expensive for what it was, and it included sound deadener and pre-cut insulation for almost every part of the car. When I insulated the car’s interior the heater box was installed. This prevented me from installing the firewall insulation at that time. Now that the heater box was removed I took the opportunity to work on the firewall insulation. The factory firewall padding was still partially in place on the firewall. It was simple to remove since after 50 plus years it was pretty much falling apart. That left me with a fairly clean and bare firewall to work with.

I searched through the insulation pieces I had left from the Quiet Ride kit and located what I thought must be the firewall insulation. At first I was unsure how it fit because all the other pieces I had installed had cutouts in them and it was obvious where they fit the car. This piece ended up fitting the passenger side of the firewall and only had a small cutout for what I thought must be the transmission tunnel. I eventually realized that the cutouts must be missing so that the piece could fit either the factory A/C cars or those with only factory heat.

I held the insulation against the firewall and marked where the blower motor and heater hose cutouts should be. Next I made the appropriate cutouts. Of course the new evaporator box will require some additional cutouts for the evaporator mounting points. I decided the best way to accommodate these cutouts is to hold the insulation up to the evaporator box before I install it in the car. That way I can mark the insulation and make the cutouts. Then I can install the insulation and the evaporator after I cut the insulation to fit.

While I was going through the couple of insulation pieces I had leftover in the kit I installed a couple of small pieces that fit around the edges of the trunk. I still haven’t identified any one piece that fits the driver’s side firewall, although I do have several small pieces. If I can’t find anything that fits or can be pieced together I plan to use some spare insulation I have laying around.

I’m not sure I ever expected to revisit the insulation after all this time, but I’m glad I’m finishing up the few areas that remained. That pretty much completes the insulation except under the hood and trunk lid. I don’t plan to insulate either of those as the insulation would be visible. Everything else is mostly hidden behind carpet and trim pieces.

So several years after insulating the car you might wonder if I feel it was beneficial. I believe it was. When I mention at car shows all the work I did with sound deadening and insulation I have received comments that there is no benefit in doing all that work and that it was wasted time. One way to demonstrate how well it works is to tap on the roof of the car and show there is only a muffled thud rather than an oil can effect compared to a car with no insulation and sound deadening. The interior of the car is much quieter and the temperature is more controlled than it was prior to adding the insulation.