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Topic: 81 CAT DELETE

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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81 CAT DELETE (1/11)
 2/23/23 1:48pm
Domer94
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NJ, NJ - USA

Vette(s):
1996 c4 coupe black / black
2000 c5 coupe pewter / black


Joined: 2/13/2023
Posts: 58

are there any readily available pipes that can bolt in to the stock location? or should i just have a shop cut / weld a piece.  also , the 81 does not have an O2 sensor as part of its CCC correct? is the computer on the 81 just for timing  , etc 

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Re: 81 CAT DELETE (2/11)
 2/25/23 11:39am
Domer94
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NJ, NJ - USA

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1996 c4 coupe black / black
2000 c5 coupe pewter / black


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so my vette has an exhaust leak... sounds like on the right side.  i was going to delete the cat and change the mufflers anyhow. after comparing cost of having a cat delete pipe fab'd up and mufflers cut out and welded in , i decided to pull the trigger on the magnaflow dual exhaust system from CC. the original cat it most likely toast anyhow. my question is now what to do with the AIR system and line. can i just cut the line where it led into the cat and leave it there? its just fresh air right?

Re: 81 CAT DELETE (3/11)
 3/1/23 3:00pm
Domer94
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2000 c5 coupe pewter / black


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bump

Re: 81 CAT DELETE (4/11)
 3/1/23 10:15pm
Adams' AppleLifetime Member
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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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If you are going that route, it would prolly be best to remove the rest of the smog system, and be done with it. You could just cut and plug the line to the cat, but then you have an air pump pumping air to...nowhere. If you simply remove the air pump drive belt, now you create a scenario where the plastic check valves/diverter valves, and other components could overheat/melt. Quickest way to eliminate the system other than removing all of it, is to remove the check valves from the exhaust manifolds, and cap the valves themselves, and remove the belt from the air pump.



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Re: 81 CAT DELETE (5/11)
 3/2/23 3:28pm
Domer94
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thanks , so if its just air thats getting blown out of that pipe, can i just let it blow? theres no exhaust gasses or anything coming out of that line to the cat right?

Re: 81 CAT DELETE (6/11)
 3/2/23 8:38pm
F4GaryGold Member
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Or air is blown into it...



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Re: 81 CAT DELETE (7/11)
 3/2/23 8:51pm
Domer94
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ok , so either way , just leaving it open shouldnt be detrimental.  ill have the true dual exhaust in there with the magnaflows soon

Re: 81 CAT DELETE (8/11)
 3/2/23 9:50pm
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No...that is NOT just fresh air being blown into the cat. There are exhaust gases in the mix that come from the exhaust manifold, that are mixed with fresh air(diluted) inside the air pump, and then piped into the cat to be burned. It is these gases that help "ignite" the unburned fuel in the cat to make it work properly. Easiest thing to do would be to remove the check valves, and find a cap to put onto the pipes on the manifold....and remove the belt from the air pump. This would completely eliminate a functioning system, and you would have no issues.

 



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Re: 81 CAT DELETE (9/11)
 3/2/23 10:56pm
F4GaryGold Member
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I'd remove the whole air pump system and use pipe plugs on the exhaust manifold. 



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Re: 81 CAT DELETE (10/11)
 3/3/23 12:59pm
Domer94
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i appreciate the definitive answer on this. i think i will try to go the route of removing the system. this is a nice driver , not a concours restoration.  from anybody that has done this, do you have an actual suggestion for the pipe cap? does it have to be welded ? etc

 

or i can see if the shop can tie the piping into the new exhaust pipe with some cut / weld



|UPDATED|3/3/2023 9:59:06 AM (AZT)|/UPDATED|
Re: 81 CAT DELETE (11/11)
 3/4/23 9:15pm
Domer94
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NJ, NJ - USA

Vette(s):
1996 c4 coupe black / black
2000 c5 coupe pewter / black


Joined: 2/13/2023
Posts: 58

so ive been searching through some threads about smog system removal / cat delete etc etc. but i need advice specifically for the 81 . will i mess up the computer by removing the smog system and cat?  i see by the pump there are some electrically operated devices / solenoids that i assume operate with the computer.  just to be clear , the removal of this system and cat will just require capping off one fitting on each side exh manifold( the one going into the check valves)?  also , just unplugging those electrical connections and tying off someplace will be ok?  would it be best to leave the AIR system electronic valves plugged in so the computer still detects them?

 

option 2 is to just remove the belt and move on with my true dual system while just cutting the AIR pipe to the cat where it is.  does the 81 have an O2 sensor? and with it gone will it throw CEL's?






|UPDATED|3/4/2023 6:15:52 PM (AZT)|/UPDATED|
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