Okay guys, I took the time today to gut my stock cats in my exhaust manifold.
A quick description of why. Basically (as you will see in a few) a catalytic converter helps filter your exhaust gasses to prevent having high emissions. This does however restrict air flow tremendously. So by removing all the material inside of the cat, you are reducing back pressure by freeing up airflow and providing more hp.
If anyone want to know how effective this is, ask Akley. He use to have the RRE headers and sold them, then gutted his stock headers. He says that he can NOT feel a difference between the two. As for my self, I have felt a significant difference in low end, and also from about 70-100.
Now lets get started.
1. First remove the positive terminal from your battery.
2. After that, remove the intake manifold cover (there is a reason for this. )
3. Now, we need to remove the drivers side o2 sensor. You will need a special tool that looks like this: (pic of it sitting on top of an o2 sensor. ) You can get this from any auto parts dealer.
![Image]()
This is simple, first unplug the o2 sensors. The plugs are on each side of the valve cover, should be a black one (rear o2), and a grey one (top o2) on each side.
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Now use your fingers or a set of pliers to bend the little clips on the heat shield that hold the o2 sensor wires.
![Image]()
Use the tool to get the sensor broken loose, Be very cautious of the sensor wires, because they will twist also. After a couple turns, you should be able to do it by hand. This takes patience. After a few turns the o2 sensor should pull right out.
![Image]()
4. Okay now, don't worry about the other o2 sensor right at the moment. It's too tight and the tool you have (at least the one I had) will not fit. What you need to do is remove the bolts that hold the heat shield on. There are four of them
![Image]()
![Image]()
The 4th one is right in the middle, across from the radiator.
5. Now that you have that off, pull it back as far as you can. You should be able to see where the exhaust manifold bolts to the head. Locate all 6 14mm nuts that hold the exhaust on, and break them loose. If they are seized up, just be easy with them, and patient. Last thing you want it to break off a stud and be without a drivable car :/
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![Image]()
6. Before you go any further up here, we need to drop underneath the car. I jacked up the drivers side nice and high so I could fit under, and secured it with a jackstand. You need to look at where the header bolts onto the exhaust. There should be two nuts and one bolt. The nuts are 16mm I believe and the bolt is 14mm. I may be wrong. Break these loose and take them all off.
![Image]()
![Image]()
7. Once unbolted just pull the exhaust pipe down off the two studs (there should be a gasket that will fall down also), and down a bit more to get it as far out of the way as possible. Now, I don't have a picture, but directly across from the 14mm bolt we took off should be another bolt, this one a bit bigger, holding the header to a mount. Take this bolt out. This allows us to move the header around and get it out.
8. Now jump back up, and remove the six 14mm nuts we broke off earlier. Behind each nut should be a washer, so make sure to grab them as you take the nuts off. There should also be a little heat shield connected to three of the bottom bolts that will come off.
9. Once those bolts are off you may or may not have to break the headers away from the head, due to oxidation. I did, because I have 120k miles and they were rusted on. I just use a rubber mallet, and a paint can opener. Just be very careful not to chisel away at the gaskets.
10. Once they are loose, pull the header off, and lift it up and sit it on top of the valve cover. I removed my manifold cover because I painted it and didn't want to scratch it up. Now grab the exhaust shield and slide it down the wire of the passenger o2 sensor to get it out of the way. Should look like this.
![Image]()
11. Now remove the other o2 sensor. Should be pretty easy to get to now. Once again be very careful with the wires. After it is off, sit it to the side, and take the manifold completely out of the car.
![Image]()
Now lets take a look inside of the manifold to see how restrictive our airflow is. Look from the bottom, directly into the cats.
![Image]()
See the white? That is the material in between, and wait til you see what it is!!
Another cool thing is flip the header back to right side up, and try blowing into each tube. When I did this the air bounced right back and hit me in the face.
12. Now you need a cro bar and a rubber mallet hammer. Take the header (bring a trash can) out to the yard or somewhere with a soft surface. Flip them upside down, and either have a friend hold them, or do like I and hold it up with your foot or knee. Put the crow bar inside the cat, and beat the hell out of it with your mallet. bust through all that material, scrape it out, turn it over and shake it out, pull it out with you hands. This material consists of a cotton like substance, and a ceramic or almost fiberglass like solid material. NO WONDER OUR AIRFLOW IS SO RESTRICTIVE!!
Once you are done (use a flashlight to view inside) try blowing through each tube again, should be a straight shot. If not, you've got some material in a tube and need to shake it out.
It looks like this:
![Image]()
![Image]()
And the end result!!
![Image]()
You can ACTUALLY see light!!.
13. Now put everything back together exactly how you took it apart, make sure all the bolts are TIGHT, so no air leaks, and take her for a drive!!
You will notice an increase in power and sound without a doubt, and i would say even gas mileage.
There you go guys, if any questions, please feel free to ask! Thanks!
A quick description of why. Basically (as you will see in a few) a catalytic converter helps filter your exhaust gasses to prevent having high emissions. This does however restrict air flow tremendously. So by removing all the material inside of the cat, you are reducing back pressure by freeing up airflow and providing more hp.
If anyone want to know how effective this is, ask Akley. He use to have the RRE headers and sold them, then gutted his stock headers. He says that he can NOT feel a difference between the two. As for my self, I have felt a significant difference in low end, and also from about 70-100.
Now lets get started.
1. First remove the positive terminal from your battery.
2. After that, remove the intake manifold cover (there is a reason for this. )
3. Now, we need to remove the drivers side o2 sensor. You will need a special tool that looks like this: (pic of it sitting on top of an o2 sensor. ) You can get this from any auto parts dealer.
This is simple, first unplug the o2 sensors. The plugs are on each side of the valve cover, should be a black one (rear o2), and a grey one (top o2) on each side.
Now use your fingers or a set of pliers to bend the little clips on the heat shield that hold the o2 sensor wires.
Use the tool to get the sensor broken loose, Be very cautious of the sensor wires, because they will twist also. After a couple turns, you should be able to do it by hand. This takes patience. After a few turns the o2 sensor should pull right out.
4. Okay now, don't worry about the other o2 sensor right at the moment. It's too tight and the tool you have (at least the one I had) will not fit. What you need to do is remove the bolts that hold the heat shield on. There are four of them
The 4th one is right in the middle, across from the radiator.
5. Now that you have that off, pull it back as far as you can. You should be able to see where the exhaust manifold bolts to the head. Locate all 6 14mm nuts that hold the exhaust on, and break them loose. If they are seized up, just be easy with them, and patient. Last thing you want it to break off a stud and be without a drivable car :/
6. Before you go any further up here, we need to drop underneath the car. I jacked up the drivers side nice and high so I could fit under, and secured it with a jackstand. You need to look at where the header bolts onto the exhaust. There should be two nuts and one bolt. The nuts are 16mm I believe and the bolt is 14mm. I may be wrong. Break these loose and take them all off.
7. Once unbolted just pull the exhaust pipe down off the two studs (there should be a gasket that will fall down also), and down a bit more to get it as far out of the way as possible. Now, I don't have a picture, but directly across from the 14mm bolt we took off should be another bolt, this one a bit bigger, holding the header to a mount. Take this bolt out. This allows us to move the header around and get it out.
8. Now jump back up, and remove the six 14mm nuts we broke off earlier. Behind each nut should be a washer, so make sure to grab them as you take the nuts off. There should also be a little heat shield connected to three of the bottom bolts that will come off.
9. Once those bolts are off you may or may not have to break the headers away from the head, due to oxidation. I did, because I have 120k miles and they were rusted on. I just use a rubber mallet, and a paint can opener. Just be very careful not to chisel away at the gaskets.
10. Once they are loose, pull the header off, and lift it up and sit it on top of the valve cover. I removed my manifold cover because I painted it and didn't want to scratch it up. Now grab the exhaust shield and slide it down the wire of the passenger o2 sensor to get it out of the way. Should look like this.
11. Now remove the other o2 sensor. Should be pretty easy to get to now. Once again be very careful with the wires. After it is off, sit it to the side, and take the manifold completely out of the car.
Now lets take a look inside of the manifold to see how restrictive our airflow is. Look from the bottom, directly into the cats.
See the white? That is the material in between, and wait til you see what it is!!
Another cool thing is flip the header back to right side up, and try blowing into each tube. When I did this the air bounced right back and hit me in the face.
12. Now you need a cro bar and a rubber mallet hammer. Take the header (bring a trash can) out to the yard or somewhere with a soft surface. Flip them upside down, and either have a friend hold them, or do like I and hold it up with your foot or knee. Put the crow bar inside the cat, and beat the hell out of it with your mallet. bust through all that material, scrape it out, turn it over and shake it out, pull it out with you hands. This material consists of a cotton like substance, and a ceramic or almost fiberglass like solid material. NO WONDER OUR AIRFLOW IS SO RESTRICTIVE!!
Once you are done (use a flashlight to view inside) try blowing through each tube again, should be a straight shot. If not, you've got some material in a tube and need to shake it out.
It looks like this:
And the end result!!
You can ACTUALLY see light!!.
13. Now put everything back together exactly how you took it apart, make sure all the bolts are TIGHT, so no air leaks, and take her for a drive!!
You will notice an increase in power and sound without a doubt, and i would say even gas mileage.
There you go guys, if any questions, please feel free to ask! Thanks!
