I looked around for a permanent solution to neatly remove the sound tube my 2017 V6 Camaro and was not really happy with anything I found commercially.
**Notes-** The intake plugs on a V8 are a different size than on a V6. The V6 intake tube opening is 30mm in diameter. So the intake caps shown here will not work for a V8. However the firewall plug will work on either one.
I recently posted an alternate version of this set which is a bit simpler to print and install. It also includes intake tube plugs (several versions) that will fit V8 intake tubes (24mm openings). Here is a link to it- https://www.thingiverse.com/thing:3267691
**First the firewall plug-**
This will fit any gen6 Camaro with a V6 or V8 engine. I cannot speak for any other vehicles, but if equipped with a "sound tube" having a firewall end such as the one shown, it should work.
I designed and printed a plug to replace the firewall end of the "sound tube" and plugged the air intake tube with a rubber cap originally (various sources sell them as chair leg tips). Later on I made a custom cap for the air intake end (see below). The original tube end has two tabs that engage notches in the edge of the firewall hole. When designing my own replacement I duplicated their positions and sizes and also strengthened them quite a bit by adding fillets.
I printed this in ABS because of the under hood temperatures and because I could acetone vapor polish it to increase its strength. You can probably get away with PLA, but you will need to be very careful about layer adhesion. In either case the plug face is likely to be slightly porous so you will need to seal it to prevent noise and vapors from the engine compartment from entering the cabin. For ABS this is quite easy, just pour some ABS juice into the interior of the plug shaft, swish it around so that it coats everything, and pour out the excess. That might also work for PLA, but most likely a coat of silicone RTV would work better.
When the print is cleaned up, you will need to add gasket material to the face of it where it meets the firewall. I used 1/8" thick "Frost King" pipe wrap (closed cell foam) but almost anything similar should work. If you have 2" wide wrap, you can simply cut a doughnut circle of it and it will work perfectly by stretching it past the tabs. If not, you will need to patch together a seal from narrower strips. Do not go too thick on this because you will have to compress it to install it.
When installing the new plug, engage the two tabs into the notches in the firewall opening, then push to compress the gasket foam and twist counterclockwise to engage the fastening stud. Re-use the original clamping nut.
It made a very large reduction in the low pitched rumble in the passenger cabin and even reduced road noise (which must have been coming in through the tube). The cabin is now much quieter and more pleasant and the natural engine sounds can still be heard, only to a considerably less extent. **Side benefit-** The stereo system sounds even better because it is not competing with engine and road noises.
I left the support material in the face of the plug because I thought it looked interesting and might be more like something the factory would do ("reinforcement ribs"), there is no structural need for keeping it.
**Now the intake tube plug-**
The following only applies to V6 cars. For V8 cars please refer to my posting of alternate styles at- https://www.thingiverse.com/thing:3267691
I didn't like the unfinished look of the chair tip cap I had used at the intake tube opening so I decided to plug it with an expanding rubber plug (Dorman 02602, available from most auto parts stores) and a custom printed cap.
This Dorman rubber plug is a very tight fit, but with a **thin** film of lubricant it can be stuffed completely up into the intake pipe hole so that it is flush with the outer edge. Examples- Vaseline or white grease. Just barely wet the rubber plug so it looks shiny. Use lubricants sparingly or the plug can pop out when you tighten it up!! Don't use the large metal washer they supply with it and use the printed cap instead. Put the cap over the plug's center bolt and push the cap firmly onto the intake pipe. Then use the original nut to secure the cap in place and to expand the rubber plug so it won't slide out. Tighten so it is snug and won't come undone but **don't** get crazy with the torque on it or you could split the intake pipe (which is an expensive part). If this causes you any potential concern, please check out my other posting on this subject which contains two plugs that are much more gentle to the intake duct and don't require purchasing the rubber stopper at all. https://www.thingiverse.com/thing:3267691 The end result looks more like a "factory" thing and is very inconspicuous. Most people would never realize it was not original if you didn't tell them. As with the firewall plug, I printed it in ABS, sanded it lightly and vapor polished it so that it looks slick and molded. The camera flash on the photo makes it look rather crude, but it really does just sort of disappear underneath the intake tube. If in doubt, paint it with some matte or flat black paint. :-)
Don't be surprised if you need to re-tighten it after a few days because the rubber plug will change shape a bit, but it shouldn't fall out. I had to tighten mine slightly twice in about 3000 miles but since then I have replaced the intake tube plug and cover with a different design (see https://www.thingiverse.com/thing:3267691 ). It is even simpler to install and has not loosened at all from the time of installation.
There is also a second version of the intake tube plug which should allow you to use the original washer as supplied with a Dorman 02602 rubber plug. It is 2mm larger in diameter and is slightly thicker on the base for added strength. But again, the versions I posted on the other link are easier to install, although the covers shown here could be used by gluing or screwing them to the plug sets at the other link.
Again, neither of these intake plugs will work for V8 cars. Please see my other posting link for updates on a V8 version. Thanks very much for viewing this.