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Submitted by pro-five-oh / 05-19-03 (rev. 03-13-04)


If you like a little more "growl" to go with your Mark VIII, you will want to remove the air silencer/resonator and drill out the lower air box. This not only ensures that the 32v masterpiece under the hood is getting all the air it needs, but it sounds great too!

The Mark VIII silencer reduces the air box's breathing area from a 4" hole in the body to a 1½" tube on the intake tube.  I'll spare you a dissertation on fluid dynamics, but the Mark VIII's air silencer and resonator are designed to quiet the rush of air by restricting and/or inducing turbulence into the intake.

Frequently Asked Questions
  1. Will removing the silencer/resonator give me more power?

  2. Yes and No. Yes, because dyno tests on Mustangs have shown anywhere from 1-5hp with the removal of the silencer and the installation of a K&N panel filter. No, because a gain of about 20hp is necessary in order for a human to "feel" a difference.

  3. Will I get better fuel economy?

  4. Probably. The engine no longer sucks air through a straw, and the lack of a silencer makes the system more efficient. Your results will vary.

  5. Will this part affect my emissions controls and yearly testing?

    No. I have removed the silencer(s) from a variety of Ford products and none of them have failed the dyno-based emissions testers here in Texas. This is a muffler, not an active part of the emissions control system. Rest assured, its obscure design and location is well beyond the scope of any emissionstest.
All models

Resonator removal:
(1993 - 1996 models only)
This is a fairly easy operation; it involves removing the beauty cover on the engine, which is a series of bolts as shown in this diagram
From there, you will see the resonator attached to the back half of the air tube. Removing the resonator requires sliding it off any of the bolts attached to the engine and unscrewing the hose clamp at the air tube.
When done, you will see a 1½" hole in the air tube. This must be capped off immediately, so make sure to purchase a 1½" plumbing cap cover (find it at Home Depot near the PVC piping) before you remove the resonator.
With the cap in your hand, slide it over the exposed hole on the intake. The plumbing cap will come with a new hose clamp, so use that to cinch the cap over the hole.
You have completed the first part of the process! It is a good idea to leave the engine cover off to allow easier access to one of the four screws that holds down the air box for the next part of the procedure.

Drilled-out Air Box

To start, remove the air box assembly from under the hood. This requires unscrewing the four screws: a 4-6" screwdriver will make removing the lower 2 screws a breeze. Remove the air box from the rubber tube on the intake.
With the upper air box gone, remove the air filter. You may wish to install a K&N panel filter later, but since it will be about $50, it is not required.
This is the fun part. With a large drill bit (I used a ¼" bit) drill a series of holes along the wall of the air box.  Drill only the leading edge of the air box; the part that is directly behind the headlights. This ensures that the air box inhales air from the two holes behind the headlight, and not from the hot engine and radiator. You may wish to bore out the holes with a Dremel tool to make the edges smooth. Make sure all plastic debris is removed and then set aside the lower air box for future installation.
Silencer Removal

With the lower air box removed, you will see 3 bolts on the body that hold the air silencer to the car. Unbolt these and then make all preparations to safely get the passenger side front wheel up in the air. This includes turning off the air suspension switch in the trunk, jacking up the car and removing the passenger side front wheel.
Now the plastic fender liner must be removed from the car. Unscrew the 3 screws that hold the front of the fender liner to the fender, and unscrew the 3 screws that hold the liner to the bottom of the bumper.
There are three plastic plugs that hold the fender liner to the car, two of which need to be removed to have access to the area where the air silencer is. Use a fork shaped tool to slide out the plastic pin that holds the fender liner to the frame.
NOTE: only pull on the pin, not the entire plug, as this will break it.

Now peel back the fender liner and start removing the silencer.
With the liner gone, you will see a wiring harness attached to the silencer. This harness can be disconnected with a forked-tool, and can be reinstalled up in the body after the silencer is removed.
First, twist off the rubber mounts that are visible on the back end of the silencer. One of these mounts has the rear screw of the air silencer, so this step really helps you get the silencer out!
Though not required, taking a Dremel tool to the front screws (from under the hood) will pop the bolts of the silencer off of the body. Once the bolts are free of the body you will need a large screwdriver or pry bar between the body and the silencer to pop the rim of the silencer off the body.
From under the hood, you can see the black rim of the silencer. This rim needs to go under the sheet metal for the silencer to slide out of the car. Use the pry bar of your choice to push it down. When the rim is clear, begin wiggling it out from the underside, but don't go crazy down there: the air suspension lines are right below the silencer.
When the silencer comes out, you can re-install the wiring harness that was attached to it using a stock hole in the sheet metal under the air cleaner assembly.


Before you finish, you might want to consider replacing the fuel filter, as it is on the opposite side of that wheel well. Reverse the procedures stated above and everything comes back together with little or no drama. Removing the silencer, resonator and drilling out the air box gives you a nice growl from 3000-6000rpm, especially in 2nd gear when you can really feel the pull of that DOHC motor. Now your Mark VIII will growl with authority when you step on the gas!

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