Richard Cooper

I just removed my catalytic converter and replaced it with a test pipe. My question is, what do I do with the steel pipe that I removed from the converter? It seems to go to the AIR pump so should I just plug the end of the line and remove the belt from the AIR pump? Or, should I remove the whole AIR pump from the car. Will the pump go bad if its not used, like seize up? Thanks for any help. By the way, I removed the converter because it was shot and there was something bouncing around inside it and I have had the test pipe for a long time just lying around.

Paul Borowski

Hello Richard, What's new??? I'm not an '81 specialist, but on the posts I've read here about removing AIR pumps is that it DOES NOT affect anything other than maybe "emission" testing. Also, I believe the '81(and 305/automatic computer 1980s)had a unique catalytic converter-pancake style but with that air tube you're referring to. Would'nt hurt to now just remove the whole pump and related hardware except what I'm not sure about is how the "computer" might react to this set-up? Along with the carb, I know '81s had part of or the AIR diverter valve "wired"? to the computer. Probably would hurt either just to let the pump "run" on the car and just let it blow air out that pipe. Another thing which I'm not sure of that the AIR pump putting fresh air into the exhaust manifolds and what effect would it have on your oxygen sensor IF you removed the belt from the AIR pump and DID NOT use it. Maybe other '81 owners will chime in here and explain what they've done in a similar situation on their '81. :yesnod: :seeya

ROD NOCK

Rich-
You're right, that 'pipe' is another outlet of the A.I.R. pump. The simplest thing to do is just fasten it to keep from rattling. Or, you could just remove sys if orig emissions aren't concern. If plugged, air will be forced out the 'relief' valve underhood. No harm, just noise. If not plugged, again, no harm, just some noise. Personally, I would rather rmve sys than just disco belt. Less dead weight, more eng comp access. Pump will eventually go bad underhood, unused, from corrosion/dirt.
For you and others reading this: if you have an 'orig' cat converter on your C3, beware that they plug-up due to design. They may check OK at idle, but can cause probs on accel and cruise conditions. High flow cats are the answer for repl. Ganey's "Exhaust Post" is good follow-up reading in Tech Tips!
Good Luck -Rod :chevy

gerry c

I also have an '81 and have looked abit at the system. From what I can see, unless you want to remove the computer and change the carb, the safest thing would be to fasten the tube from the air pump so it does not rattle and leave it on a flowing. The pump injects air upstream of the O2 sensor and if you remove the air the pump is injecting, you MIGHT start running even leaner since the O2 sensor will see a slightly richer state. It may not make much of a difference but I am not sure.

Good luck with however you go, I wish I could do stuff to mine but our smog people are impossible.

rjs82vette

You can remove the whole AIR pump and all the hardware without affecting the car in anyway... It is just for emmisions and doesnt do anything else...

The Computer: when the car is cold the computer sends power to the AIR diverter valve to divert air into the Exhaust manafold before the O2 sensor so that the O2 sensor detects a lean condition and add more fuel so that the car will run rich.... when the engine is cold it will run smoother and warm up faster if it is getting a little more gas.... when the temp sensor tell the computer that the engine is warm then the computer stops power to the AIR diverter valve and the valve diverts the AIR to the Cat... more air in the cat helps to burn hydrocarbons....

since the computer never gets any information from the AIR diverter valve or the pump it cant tell if its there or not..... So you can disconnect it and remove it....and your car will run the same.... may run a bit rougher when its cold...

81VETTOM

Richard;
I added a hi-flow Random Technology convertor (smaller, lighter and more flow) back to mine. Since I live in a emission state, has to have one. There is a small pipe on it, which was connected so it could be removed later, if service was needed. I can tell a real improvement. I am unsure what leaving the pipe open would do. What you heard bouncing was probably the element, some pieces probably broke inside, causing more restriction. All this was made to run in place. So, unless you can remove all that, you still have a really simplton ECM on board to deal with. For us 81'ers we just got a one of a kind Vette. :smash:

Ganey

As Rod said, it will also go bad from being exposed to weather off the car. What I heard.

:cool:

Richard Cooper

Thanks to all for your help, I was worried about starting the car before I knew if it would hurt anything. Now, I will start the car and if its OK I will remove the complete system. My son-in-law does my inspection every year so I am not worried about inspections.
Thanks again for all your help and explanations you guys and this site are GREAT.

Biker

I have a test pipe on my '81. The pipe came with a tube that allows a connection from the air pump hose. I found my test pipe on ebay. Unfortunately, my car will not pass emissions in Illinois with the test pipe installed (I found this out the hard way, forgetting the pipe was installed on the car.) For this reason, I now install a high flow catalytic when I have the car tested at an emissions station. Thank goodness for the flanged pipe joint, which allows me to complete the swap in about 15 minutes.

Richard Cooper

Biker,
I got my test pipe from Muffler Tech in California and there is no fitting for the steel line.