2018-2020 Mustang GT ROUSH STAGE 4 Inlet Path Sound Tube Installation Guide SKU 875

2018-2020 Mustang GT


Sound Tube Installation Guide SKU 875, Ef650

Image Above : Stage 4 Kit

This kit requires that the firewall is drilled.

  1. 1 x drill bit
  2. 1′′ straight hose barb
  3. 1 x diaphragm cap
  4. 1 x Blade
  5. Sound Tube
  6. 2 x rubber Grommets 1 Large and 1 small groove
  7. 1 x Zip tie
  8. Grease

Fold the carpet down in the driver side foot well behind the brake pedal to the left of the steering column & secure by inserting a small screw as shown in the image through the carpet.Pull the retaining clip off the carpet stud to enable the cutting of the insulation.Cut the insulation along the horizontal line with supplied blade.Fold the insulation out of the way by tucking it up and down behind itself.

Use a center punch to mark the drilling point for the hole. Draw a line across from the steering column bracket point. Draw a second vertical line approximately ¼” from the raised sheet metal contour as shown the image.

To determine the exact point, you will be able to feel (using your fingers) After using the center punch to mark the drill entry point, drill a pilot hole first then using the supplied drill bit at low speed and using windex as lubrication and cooling to avoid (overheating) and damage to the drill bit. Drill on low speed and keep pumping the windex flooding the bit.

Make sure the drill and hole saw is flush with the fire wall sheet metal as not to catch and edge and damage drill bit. Drill all the way through with the bit. WATCH VIDEO BELOW

Use protective cloth or paper towel taped to the firewall to catch the drill debris and filings produced during the drilling process. Vacuum filings after drilling.

With supplied bit drill a hole in the side of the inlet pipe slightly upward (see diagram below). Clean the edges with a razor or sand paper then install the narrow groove grommet into the hole, making sure it’s completely seated Red circle indicated the area to drill. See Video below.

After rubber Grommet is installed push the 1” hose barb into the grommet from the inside with supplied grease to help seat and seal. the new hose barbs are black and have one rib. Watch Video.

Push the sound tube over the hose barb while holding it from inside. Fully seat the sound tube so it’s completely compressed against the housing and grommet. Use supplied grease will help in seating the sound tube to the hose barb. This step needs to be done before inlet is replaced.

Install the supplied wider grooved grommet working into the hole which was cut in the firewall. Use supplied grease on the bare metal edges for protection. Add some grease to the grooves of the grommet to prevent corrosion.

Install the sound tube through the firewall hole with wider grooved grommet in place. It should be possible to fit your entire arm into the space and your hand all the way to the firewall.

Use supplied grease inside the grommet and on the tube end which will aid in pushing the sound tube hose end through the grommet in the firewall.

Watch video

This illustrates how the cap would install to the sound tube. Some diaphragm caps may fit over the tube instead of inside. This doesn’t affect form or function

Warning: failure to install the diaphragm cap properly could result in unmetered air and a lean condition.

Fold back the carpet insulation into its original position
and use the supplied blade to trim the edge of the carpet to the diameter of the sound tube.
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