If you didn’t think Corvettes are cool you wouldn’t be reading this magazine, but let’s face it, Corvettes were never famous for being thermally cool. Actually the opposite is true, early Corvettes are notorious for interior heat. This invasive heat and noise is due to the fiberglass construction of the car that tends to vibrate and carry noise, while the tight confines of the engine bay is a huge source of unwanted interior heat and noise. The same goes for the transmission tunnel that rises up between the driver and passenger. The whining of gears and additional heat is transmitted through the floor and transmission tunnel, and we haven’t even mentioned things like mufflers. Compounding the unwanted interior noise and heat problem are the antiquated sound damping and insulation products that were available in the ’50s and ’60s.
One need only take a ride in a brand-new Corvette (or even a modern base transportation car) to realize just how far we have come in this noise and heat game. While a new Corvette produces more than double the horsepower of the 1960 model (and horsepower is heat) the interior is cool and the happy sounds emanating from the tailpipes do not vibrate the car at all. Yes, it’s 2016 and a lot of things have changed for the better. Happily, we now have solutions for vintage Corvettes.
So how do you go about bringing a modern lack of sound to your vintage Corvette? As it turns out, the solution is really quite easy and well within the reach of any Corvette enthusiast. We began by placing an order into Design Engineering (DEI) for a Boom Mat Thermal & Acoustic Interior Kit. This kit contains pretty much everything you’ll need to minimize vibration and heat transfer in your Corvette. It begins with Boom Mat, a can of Boom Mat Spray-On for hard to reach areas and an ample supply of Under Carpet Lite, which is true insulation. We also ordered a can of Boom Mat High Temp Adhesive spray for attaching the Under Carpet Lite to the firewall. We also included the Boom Mat roller and utility knife in the order. I’m a tool junkie and for the record this is the nicest utility knife in my toolbox. Armed with the proper tools and material we began the project.
First, it is imperative that the floors and surfaces to be covered are as clean as possible so the Boom Mat will adhere properly. Believe me, this stuff really sticks but a layer of dirt and heavy grit can limit adhesion. With a suitably clean surface it is time to begin placing the Boom Mat in the car.
We began with full sheets. By tacking in few sheets with the plastic backing still in place we were able to see where a full sheet would fit and how much cutting it would take to fill in around the full sheets. Satisfied with these locations, we began to adhere the full sheets in place. Like any sheet application, the idea is to have the sheet lay down with no air bubbles or pockets. We found that peeling back the plastic to about half-sheet and then placing the Boom Mat in place worked well. Then, using the roller we pressed the Boom Mat firmly in place. Between the full sheets we used the utility knife to cut additional sheets to fill in the different spaces until the entire floor and firewall were seamlessly covered. This layer of Boom Mat has the primary function of eliminating unwanted noise and vibration transfer, and while it does have some insulating effect it is not considered primarily as insulation. You will also note we did not put Boom Mat on the flat surfaces where the seats bolt down. We did not want compressed material between the seat frame and the floor and we also value every partial inch of headroom in a C1.
We then moved to the trunk and lined everything we could reach with Boom Mat, once again a cut and roll installation. One large source of interior noise is the tires. Going down the road tire roar can really wear on you. While we used conventional Boom Mat on the rear sections of the wheelwells, we used Boom Mat Spray-On to sound-deaden the tops of the wheelwells that were not accessible with the Boom Mat sheets and roller. It is also worth noting that while complete coverage is ideal, partial coverage—such as inside the door—will provide enough sound damping to provide the desired “quality thunk” when the door is latched shut. After the car was completely lined with the sound deadening material we moved on to the insulation.
DEI has a product called Under Carpet Lite (UC Lite) that truly is light and easy to use. If you don’t have a pair of quality scissors we suggest you buy some before beginning the job. You can use the utility knife but we found our upholstery grade scissors made quick work of cutting the Under Carpet Lite. Using the DEI spray adhesive, we put a coat of adhesive on the insulation and a coat on the firewall and allowed it to flash dry. This makes the adhesion very strong and very quick. In fact, the adhesion is so good it is imperative that you start in one corner and the press the piece in place. There is no sliding of the piece, so get it right the first time or you will have to pull it off and start over. Of course, installing firewall insulation is not a thousandth of an inch accurate process so the installation goes quite easily. We insulated the entire firewall and top half of the floors. We also insulated inside the kick panels and the trunk partition between the trunk and the gas tank. This insulation will keep upwards of 85 percent of the heat out of the passenger compartment, and the carpet will add even more sound deadening in the process. We did not install UC Lite on the floor area since we still had to install our Vintage Air unit. Boom Mat makes it easy to slide on the floor so the UC Lite will go in just before the carpet.
After the insulation was completed we covered our Corvette Central trunk partition with leather using the same DEI adhesive. For added good looks we added a set of Corvette flags that were original to the car but had a broken pin, so this was a great way to use the old part. That completed the heat and insulation of the passenger compartment. We cut a piece of insulation to go down in the spare tire well as that is close to the muffler area, which is a source of heat and noise. Likewise, we wanted the added noise benefit over the tires so both rear wheelhouses were covered with UC Lite.
This entire process will probably take you longer than you first thought if you do a neat and thorough job. But then again, everything takes more time than we plan for. We spent two full days on the project, but were more than satisfied with the results. While this is a job that doesn’t show cosmetically, it will make each and every mile you drive a more pleasurable experience.
01. While most drivers love the deep rumble of a Corvette V-8 we prefer to keep that noise outside the car. To that end, we embarked on a sound control project using Boom Mat and UC Lite materials from Design Engineering (DEI).
02. Along with the box of Boom Mat we ordered two cans of Hi-Temp Spray Adhesive and one can of Spray-on Boom Mat for hard to reach areas. We also ordered the DEI utility knife and roller.
03. Boom Mat is a foil covered, self-adhesive product that damps sound and vibration in panels. Technically, 25-50 percent coverage will damp most panels; however, we did 100 percent coverage to provide a uniform surface for our carpet set. Boom Mat also provides insulating qualities.
04. But when it comes to really beating the heat, UC Lite is the answer. The multilayer fiberglass/polyester composite material beats up to 85 percent of heat gain and adds an additional layer of sound protection, too. UC Lite can be glued inside firewalls, on floor, inside doors, and headliners. We did our entire firewall and the trunk partition.
05. The first step to a successful installation is getting all surfaces clean, oil, sand and grit free. Our floor is the perfect surface for Boom Mat.
06. Cutting Boom Mat is simple enough. Just use the high quality DEI utility knife with the mat laid out on a work bench or piece of plywood. We found cutting the pieces with a carpenter’s square helped in fitting the multiple pieces.
07. Like most sticky things, it is best to begin with just a portion of the adhesive exposed for placement, once properly placed the plastic can be peeled off as you apply the sheet.
08. After carefully and lightly placing the sheet in position it is time to get the roller out and roll the sheet smooth. Working in the proper directions so the sheet lays flat with no air bubbles is best. If you get an air bubble, slice it with the knife and continue rolling to flatten out the bubble.
09. Here you can see the plastic backing is being peeled off the sheet as we roll the Boom Mat into position. Installation is very simple, but like most “simple” things, best results are achieved through careful work.
10. The Boom Mat will conform to different shapes easily, but leave enough material to form over the curves and work your roller in one direction.
11. We use the Boom Mat to provide a smooth, uniform height floor wherever possible. Here, we are notching the sheet to help smooth out a raised part of the floor.
12. Here is the notched sheet in position, notice how it helps make the floor flatter, which makes carpet installation smoother. We did the same thing around rivets and bolt heads.
13. Making holes in the material is very simple, too. If you have a set of arch punches they work great. Fit the sheet in place and mark the desired location of the hole by pushing against the hole in the firewall. Next, punch the hole and then the plastic backing is removed from the sheet.
14. We encountered the need for holes larger than our punch set. To form the larger holes we simply ground a cutting angle on the end of a piece of tubing with our bench grinder and used the tube as a punch.
15. And this is the completed floor/firewall area. Notice we did not put Boom Mat where the seats mount. We did not want to compress that material between our seat frames and we also want the seats to be as low as possible in the car.
16. Next, we moved to the trunk area and did a similar treatment. Much of the noise entering a car comes from this area since there are two tires and two mufflers located under the trunk area.
17. The Corvette Central spare tire disc fills in the floor perfectly so our trunk mat will lay down nice and flat, but that will come during the upholstery process.
18. Now it was time to begin installing the UC Lite material from DEI. This stuff really beats the heat, something that is important in Corvettes. Once again, the utility knife or commercial scissors cut the material.
19. We covered the entire firewall and transmission tunnel with UC Lite. Here we have taped a piece in position to mark the required holes for the A/C and heater hoses.
20. This is the completed firewall. We will finish the toeboard and floors after we install our Vintage Air unit.
21. Using the DEI spray adhesive, we also covered the partition between the trunk and the gas tank well. This will control heat and noise from entering the interior from behind the seats.
22. We had ordered a factory original style molded trunk liner from Corvette Central and decided to install it at this time, too.
23. I had several large pieces of leather left over from another project so I decided to cover the panel with leather, no padding, just leather. Once again, DEI spray adhesive worked great. Crossed flags add a bit of flavor to the project.
24. This is the finished trunk area, after this photo was taken a layer of UC Lite was added to the floor of the spare tire well. While all Corvettes are cool, with a couple days work and the proper materials your Corvette could be the coolest and quietest one in town.