TTJR 81Want to replace the original system on my 81, very rusty and too quiet. I see Magnaflow makes a complete bolt on with pipes, converter and mufflers. Does the air, smog pipe reconnect as well? Looking for more sound and would like to keep motor stock otherwise. Thanks!
johnuNot sure on that one. I purchased a bolt on replacement "free flowing" cat years ago. Got a little more rumble without messing with the original system. I had to buy some heat resistant gray converter tubing $$ to complete the hookup.
manchestershark
Will it pass State Inspection without the Cat? If so, Just put a regular performance system on and enjoy it.
73sharkAssuming you are keeping the original exhaust manifolds and an OEM equivalent converter, then all the emissions stuff should hook right back up.
If your state does not require a converter then I would go with the factory side exhaust as it's an easy way to do it plus it has very nice sound.
1973 L-82 4 spd
TTJR 81So, if I don’t go with converter /stock setup what happens to the air pump smog pipe that would go to the converter? Would my computer know the difference
NorskyI've been told if a converter is removed from the exhaust system the air pump and its associated pumping can go away. I can't say for sure but would think the computer would need to be reprogrammed to not look for input from the O2 sensor(s).
Jim Olson 
"The Toys"...!!! Save the Wave! 
Dane2009Did you like the result? I have a bone stock ‘77, l48, 350. It’s all original. Before changing exhaust (because it’s just too quiet on top of slow) I was contemplating cutting the cat off and replacing with bypass tube. I figured it would sound better… does it?
I don’t want to modify it anywhere but I gotta have it sound better…
Daneja
F4GaryDid you like the result? I have a bone stock ‘77, l48, 350. It’s all original. Before changing exhaust (because it’s just too quiet on top of slow) I was contemplating cutting the cat off and replacing with bypass tube. I figured it would sound better… does it?
I don’t want to modify it anywhere but I gotta have it sound better…
Why not just go with true duals and no cats?
F4GaryI've been told if a converter is removed from the exhaust system the air pump and its associated pumping can go away. I can't say for sure but would think the computer would need to be reprogrammed to not look for input from the O2 sensor(s).
I would think on an 81 there is no after cat O2 sensor. So just use the stock sensor in the stock location.
I have an 1981 vette and the member that responded mentioning that there is no after cat sensor is correct, there is none. I have removed all smog/ air system and the car runs well without it. I just emptied the cat of its contents. Enjoy your ride
Drose
