Hi, in the process of trying to remove my differetial, but I need to remove the rear exhaust. The 4 bolts/nuts that hold the system in place on the back of the cat are all rusted and I cannot get them off. The cat itself does not look to good. If I take it to a muffler shop and have them remove the cat and just put a straight pipe in its place will that cause the engine any problems, warning lights, etc. I have the stock CFI engine still in it. Its ok to remove the cats and run straight exhaust in my state since its over 25 yrs old. Figured if they put a new pipe in place, I will be able to remove the rear exhaust with no problems in order to get to the differential carrier.
Thx,
R

 

When I run into this issue while trying to remove a rear differential I have two ways of doing it. It generally depends on 1.) How I am feeling at the time. 2.) If the nuts that hold the exhaust pipe to the exhaust manifold(s) will come loose or feel like they are going to break off.

Seperating the rear "Y" pipe from the catalytic is sometimes more of a pain to get sealed back (for me) than it is worth. I remove the entire exhaust system at a complete assembly. OR....... I remove the half shafts, strut rods and leaf spring. Then remove the differential and leave the exhaust hanging ( or slightly supported depending on the pipe integrity) I have done it with a floor jack numerous times this way. And like I wrote, it is how I am feeling and the nuts for the exhaust that will make this decision for me. Last thing I want is to spend time in getting the nuts to release and not break an exhaust stud.

AS for you removing the catalytic converter. Do what you want. But I mysefl would not. Even though your stste may not require you to go through emissions tests, some states still require that ALL of the factory emissions equipment remain on the car as part of the safety inspection.. Your oxygen sensor is before the catalytic converter and the pipe from the catalytic converter goes back up to teh airt management system for the car. Just leave well enough alone and don't "re-invent the wheel". I have a gas analyzer at my shop and I use it during a tune-up (before and after) so I can get the emissions correct. Eventhough the state doesn't care about the emissions, I need to know this data so I can get the car running correctly, or let you know that your engine is junk and needs to be rebuilt after other tests have been performed due to high emissions numbers.

'DUB'

 

You can remove the cat, car will run fine. Did this on my 82 temporary. Here is a pic. On this pipe is a wideband oxygen sensor installed if you are wondering. The air pipe coming from the engine bay is plugged.

 

How are the bolts in the front of the cat, if you can remove it fromt he front then drop the whole system, cat back. Once the system is down, cut off the old bolts and if the Cat is junk, you can replace it. I doubt if any muffler shop will replace your cat with a straight pipe. You would have to do that yourself.

 

FEDERAL law requires ALL cars to retain their factory emissions. Some states are just more stringent on enforceing these laws.
As for the cats, the new high flow cats cost very little HP, and only help with the "perception" of the car hobby as a whole.

 

Personally, get rid of the cat if you don't have an emissions inspection. My guess is you like most others drive their C3's very little and any pollution contribution is not even on the radar. I would add true duals at some point to really help your engine. If you had a fuel injected engine from the last 15 years, my opinion about the whole engine emissions issue is totally different since modern engines run great, make good power, and have excellent lmileage with the emissions hardware that was designed with the engine in mind. On C3 engines the emissions were an afterthought that were not very compatible with the motors and almost any C3 will run MUCH better without the emissions hardware and make MUCH more power since items like cats were just bolted onto the motor to meet regulations and were not designed from the outset to work with such motors. I have a 1994 Mustang GT with 4 cats, BBK shorty headers, and magnaflow mufflers and it runs great and makes good power-totally different situation with the 75-82 motors with poorly designed and very restrictive cat exhaust, AIR pumps, EGR Values, very high temperatures, etc! 25+ year old cars are not relevant for an emissions discussion compared to the millions of modern cars on the road today!

 

the ubove resposes give you all the "required responses"

I have an 82 without the cat. The 02 sensor is before the cat so you are ok. The sensor will take a little longer to warm up.

you will get a minor power increase. If you can tune then you can pass the sniffer.

 

Thanks everyone for all the replies. I luv this site... Nothing is ever easy is it..
Well the 4 bolts that attach the back of the exhaust to the cat were really rusted bad. In fact one of the bolts was missing. The end of it was sticking out the other end, but the head was gone. Tried putting heat to the bolts and half a can of wd-40, it would not budge. I think I rounded one of the heads. After a closer in spection, I noticed there was a thumb size rust hole where the two pipes y out to the rear exhaust/mufflers. So I made the decision to cut it at the y behind the cat. I did not see how I could possibly remove the differential with pipes still in place. Amazing what a SawZall will do. The cat is still in place but the exhaust now stops there. I am working my way from the rear to the engine. New diff rebuild, new trans rebuild and then new engine last. The CFI will go away. So I will eventually in the next few months have a new true dual exhaust system, headers, etc., no cat. I would like to see some pics of some 80-82 exhaust upgrades. Trying to figure out where the driver side pipe will go. Right now the exhaust comes out of the driver side and y over to the passenger side then goes into 1 pipe into the cat. There is a bend in the cross member to allow this on the pass side. I hope I will be able to get two 2.5 inch pipes thru there. OK, I have another problem, I will post a new thread.
Thanks again

 

mid america has what you want 618-975 chambered or 603-864 regular pipes