Catalytic converter pipe question..
Thread Starter
Advanced
Joined: Mar 2013
Posts: 72
Likes: 0
From: New York
Catalytic converter pipe question..
Hi all,
The factory original cat on my 81 has a leak and its time for it to go. I plan on eliminating it by putting a test pipe in its place. Hopefully that will provide a slight power/sound gain. My question is what should I do with the pipe from the air pump that feeds into the cat? Should I cap it off or would it hurt to just leave it open? I dont want to remove it completely because if I ever sell the car and somebody wants to return the car to stock it will be there.
-Thanks
The factory original cat on my 81 has a leak and its time for it to go. I plan on eliminating it by putting a test pipe in its place. Hopefully that will provide a slight power/sound gain. My question is what should I do with the pipe from the air pump that feeds into the cat? Should I cap it off or would it hurt to just leave it open? I dont want to remove it completely because if I ever sell the car and somebody wants to return the car to stock it will be there.
-Thanks
Burning Brakes
Joined: Apr 2013
Posts: 926
Likes: 2
From: Castle Rock CO
If you can get away with removing your Emission Control Systems then a test pipe it is one the way to go.
While I generally suggest not doing it because it might bite you in the butt if where you live ever enforces Emission Controls.
If you are building the engine for performance look for parts before 1975 I say this because in 1975 is when Emission Control Systems went on in California and in 1976 everything but many pickup trucks had Cats. Everything before that was practically emission free except for the PCV and a few other parts to recirculated the oil and fuel tank gases back into the engine.
Save all your parts for the day you sell it and have to put it all back on the car. You will not get a alot of horse power by removing it and the sound is not going to get much deeper. A free flow exhaust even with a cat will give you more Horsepower. Put in a set of headers and the gain gets better. It all depends how much you want to spend.
I did a test pipe on my 1976 Chevelle and did not notice a sound or increase in HP or fuel economy. It was not until I did a free flow exhaust that I noticed a difference.
You can remove the Smog Pump and plug up your EGR Valve and other emission system componets.
There are others that have asked the same question and I did a google search on the subject.
http://forums.corvetteforum.com/c3-t...-corvette.html
http://forums.corvetteforum.com/c3-t...-corvette.html
http://forums.corvetteforum.com/c3-t...r-removal.html
While I generally suggest not doing it because it might bite you in the butt if where you live ever enforces Emission Controls.
If you are building the engine for performance look for parts before 1975 I say this because in 1975 is when Emission Control Systems went on in California and in 1976 everything but many pickup trucks had Cats. Everything before that was practically emission free except for the PCV and a few other parts to recirculated the oil and fuel tank gases back into the engine.
Save all your parts for the day you sell it and have to put it all back on the car. You will not get a alot of horse power by removing it and the sound is not going to get much deeper. A free flow exhaust even with a cat will give you more Horsepower. Put in a set of headers and the gain gets better. It all depends how much you want to spend.
I did a test pipe on my 1976 Chevelle and did not notice a sound or increase in HP or fuel economy. It was not until I did a free flow exhaust that I noticed a difference.
You can remove the Smog Pump and plug up your EGR Valve and other emission system componets.
There are others that have asked the same question and I did a google search on the subject.
http://forums.corvetteforum.com/c3-t...-corvette.html
http://forums.corvetteforum.com/c3-t...-corvette.html
http://forums.corvetteforum.com/c3-t...r-removal.html
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
1. If you are not going to be replacing the cat soon, I would suggest removing the AIR line so it does not get damaged. It is a thin wall tubing and easily destroyed.
2. Replacement cats are not going to have the AIR connection in the same location so you will have to make modifications to the AIR tubing anyways; easier to do off the car.
3. No harm will come from leaving the AIR line open.
4. Good luck finding a test pipe for sale; best bet is to have a shop make one for you. The pipe is not straight. I actually have one that I bought from someone many years ago and just recently put it back on the car as it is going to the paint shop on Sept 3. I will be removing it upon the car's return home...but that will not be for about a month.
Have Fun.
2. Replacement cats are not going to have the AIR connection in the same location so you will have to make modifications to the AIR tubing anyways; easier to do off the car.
3. No harm will come from leaving the AIR line open.
4. Good luck finding a test pipe for sale; best bet is to have a shop make one for you. The pipe is not straight. I actually have one that I bought from someone many years ago and just recently put it back on the car as it is going to the paint shop on Sept 3. I will be removing it upon the car's return home...but that will not be for about a month.
Have Fun.
