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How to Install a JBA After-Cat H-Pipe - 3in to 2.75in on your 2011-2013 Mustang GT

Installation Time

2 hours

Tools Required
  • 1/2" Ratchet
  • 13mm Socket
  • 15mm Socket
  • 9/16" Socket
  • 1/2" Deep Socket
  • 1/2" Universal
  • 6" long 1/2" Extension
  • 13mm Wrench
  • Vice Grips
  • Floor Jack
  • (4) Jackstands
  • *Tuner (Optional)
American Muscle
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Please read through the instructions carefully before starting this project. Take the time to get all the materials together as well as all the safety equipment.


(1) H-pipe
(2) down pipes
(4) Bolts
(4) Nuts


1. Start by removing the new H-pipe from the packaging and inspect thoroughly for any damage. Also check to make sure that all of the necessary parts in included.

2. With the car parked on a level surface use a floor jack and stands raise the car up to a height that will be comfortable for you to work under. Always use jack stands and never trust your life with just a floor jack!

3. Locate the exhaust two clamps at the rear of the H-pipe. Using a 15mm socket remove the all four nuts from the clamps and save as the clamps will be reused. Slide the clamps forward so they are only on the H-pipe.

4. Locate the two clamps over the ball joints coming from the down pipes. Using a 13mm wrench break the two bolts free. This can be tricky because of the location but you should be able to achieve this with a little patience. After the two bolts are free use a pair of vice grips locked onto the bottom of the bolt that contains no threads and use the pliers to turn the bolts until the clamps are completely loose.

5. Pull the H-pipe toward the rear of the car and it should clear the clamps and drop down so that it can be removed from the car.

6. If you are going to leave the catalytic converters in place skip to step 7. Disconnect the electrical connector and remove the O2 sensors. Using a 9/16” socket remove the 4 bolts that connect the down pipes to the collector. It may be necessary to use an extension and a universal to achieve this. Install the new down pipes using the bolts provided in the same location. Make sure the O2 sensor holes face the center of the car. Reinstall the O2 sensors and their connections. Warning: You will need to reprogram the ECM and change parameters for the O2 sensors if the catalytic converters are removed.

7. Using a pair of pliers work the two tabs on the front exhaust clamps until they fatigue and break. This can also be accomplished with a cut off wheel or hacksaw if you so choose.

8. In reverse order as it was taken off start to put the new H-Pipe into place. Once the ball clamps are on slide the pipe clamps over the rear portion of the exhaust so the H-pipe is suspended in place. In this installation it is okay to reposition the ball clamps such that the bolt heads are no longer facing the body allowing access to them. Slowly start tightening the blots on the pipe clamps first and then on the ball clamps. Once the bolts are wrist tight with a wrench, inspect your exhaust tips and adjust them as needed to center in the cutouts. Also check for a minimum of ½” clearance around all of the exhaust. If everything looks good tighten down the bolts on all 4 clamps.

9. Install the U-bolt on the center section of the H-pipe. Make sure to orient the bolt so the ends face either the front or rear of the vehicle so there are no ground clearance issues. Using the ½” deep well socket start tightening the nut. Continue tightening until the outer pipe collapses onto the inner pipe forming a seal to exhaust gases. If desired some muffler putty can be used as well on the slip joint.

10. Re-check the exhaust system for clearance and reposition exhaust tips as needed. Following the instructions with your tuner, install a new program for your ECM. If you are reusing the catalytic converters an ECM reprograming is not necessary but is recommended as it will allow you to take advantage of the better exhaust flow.

11. Start up the car and check for any exhaust leaks. If leaks are present adjust or tighten clamps as need to correct.

12. Using a floor jack remove the jack stands from under the car and take it for a test drive. Make sure to enjoy the added power and improved sound

Installation Instructions provided by AmericanMuscle customer Kevin Cross 12.10.12

This guide applies to Vehicle years: 2011, 2012, 2013, 2014 and Submodels: Boss 302, GT