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Discussion Starter #1 (Edited)
I gutted my pups

Decided to gut my pup cats today and it was a breeze using just simple tools.

1. Unbolt H-pipe from muffler assembly
2. Remove rear hangar bracket lower bolts (on front of tranny). They're the ones that have the springs.
3. Remove the O2 sensors from just behind the main cats. It's a good idea to remove several inches of the wire from the clips on the heat shield to minimize twisting of the wire.
4. Remove the nuts that attach the exhaust to the header outlet. At this point the only thing holding the exhaust up is the front bracket where the exhaust bolts to the bell housing forward of the main cats.

I did this alone with the car raised just enough to fit under it as I do not have a lift.

5. Position your knees near the center of the whole assy. so you can use your legs to lower it when you remove the last 2 bolts (on the front hangar bracket) Once these are out you can lower the whole assy and slide it out from under the car.

6. Position the assy. on a stand or somewhere that you can have the pre-cats at the lowest point (to prevent debris from falling into the main cats)

7. Using a large straight slot screwdriver simply dig the catalyst material out of the bubbled portion of the pipe (it comes out fairly easy) Once you have the bulk of it out you'll have to fabricate a tool to scrape out the insulation that lines the bubble. (THIS INSULATION MIGHT BE ASBESTOS...WEAR A DUST MASK OR RESPIRATOR, OR DO IT OUTSIDE IF THERE IS A BREEZE TO KEEP FROM INHALING THE DUST!!!!!) I made a scraper out of an old steel ruler with a 1 inch 90 degree bend on one end to scrape out the remainder. You will need this tool to reach around the slight corner to ensure you get out all of the insulation.

8. Using a leaf blower, blow out the pipe from the exhaust end to ensure all material is removed to avoid fouling the main cats.

9. Re-install the exhaust in revers order of removal. Use anti-sieze compound on everything with threads and be careful when re-installing the O2 sensors. Put them in the hole and screw them backwards (not in) to pre-twist the wire (about 3 turns should do) then screw them in.

Whole project including raising and lowering the car was approx 3 hours. The car has a slightly more aggressive exhaust note and is noticeably louder at WOT, probably like what an 02 model sounds like and GM claims 5 additional HP with them removed.

My car has always felt very strong so I didn't notice any difference in SOTP but I recieved my MAF Translator today so once I get it wired I'll have to get a scanner to see where my fuel trims are. then off to the dyno. I think with the pups gone, my T1 intake and then dial in the fuel trims with the MAFT I should be in the 410 HP range. All for under $1000.

If anyone needs the torque values for all of the bolts...let me know and I'll post them.
:cheers:
 

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Discussion Starter #2
Update.........Torque values

All bolts are to be tightened to 37 lb/ft

Except the following:

Exhaust flange to header outlet.....15 lb/ft
O2 sensor.......................................30 lb/ft

Note: The rear hangar bracket (the one with the springs) calls for 37 lb/ft also but using this torque is enough to twist the bracket where it's welded to the exhaust pipe. 25-30 lb/ft should be plenty tight.
 

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Awsome, great ideas......
 

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Discussion Starter #4
Update.......

I have noticed that the burbling sound on decel has gotten louder. I'm not sure if it's because of the louder exhaust note or the fact that my car runs a bit rich.
 

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The louder sound you here is the absence of the material you hogged out and the fact that there is less sound absorbing charactoristics left in the pup pipe. You should be aware though, that this will actually change your emmission numbers negatively since the pups cats work in conjuntion with the post cats, they are two different materials that equal an end result. I will post you later when I find the material specs, the 2002 incorporated both materials into 1 cat to delete the pups.
 

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Discussion Starter #6 (Edited)
MrZ06 said:
You should be aware though, that this will actually change your emmission numbers negatively since the pups cats work in conjuntion with the post cats, they are two different materials that equal an end result.
I read an article once on the developement of the 02 model and how they extracted the extra HP and it said the pups were only incorporated in the 01's because the main cats were too far away from the hot exhaust stream which prevented them from "lighting off" early enough. Not because the 01 cats were insufficient. The placement of the main cats and their distance from the hot exhaust prevented them from passing a certain part of the California emissions test (cold engine startup). The pups were incorporated more as a means of transferring heat to the main cats. In 2002 GM used a slightly different style cat that lit off easier and faster allowing it to pass the Ca tests.

I've even noticed this since I gutted my pups. The exhaust smells like there are no cats for the first minute or 2 when starting it cold, but once the cats light off there is no problem and the exhaust smells normal again as if I hadn't changed a thing.

Boy, that was a mouthful.....I've been sniffing too much car exhaust:lol: :lol:
 

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Chevy Source Book:

Changes to the compisition of the precious metals in the underfloor converters enabled removal of pups.

While the 2001 underfloor converter was a single brick design coated wth a mixture of paladium and rodium, the 2002 converter is a dual brick design coated with paladium on the front brick and a mixture of platinum and rodium on the rear brick.

Another artical in Corvette Quartly stated that they incorporated all components from the '01 into one cat on the '02.

Everything for California always has to be different, ever try dealing with the DMV, pretty strict!
 

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Discussion Starter #8
You're telling me.......I lived in Ca for 8 years......what a pain. Thankfully I live in Florida now where we can pollute. Though I doubt it matters. The stock 01 cats will pass any test without the pups as long as the engine is hot. It will even pass a visual cause the cannisters are still there.
 

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If/When you perform this mod be sure to REMOVE ALL OF THE INSULATION!! There is quite a bit there. If you don't take your time & get it all, clogging or partial clogging the main cats will be the result. Not good!! In addition to blowing the assembly out from the other end with a leaf blower, it's a very good idea to use a good vaccume cleaner with the flexible hose attachment to 'suck out' small insulation particles & dust while you are scrapping & cleaning. Picking up the entire assembly and shaking it out (frequently) also helps. Don't forget to use a respirator because inhaling this dust is certainly a no-no!!

Also, when starting to break up & remove the main material, it's a very good idea to not use a sharp pointed standard screwdriver. Use a large 'phillips' head instead. This will keep from possibly punching a hole in the pup cat by accident. Also not good. The material isn't that hard & should break up fairly easily.

I've attached a picture of a tool that will come in very handy when cleaning (the insulation) the part of the pup cat that is the hardest to access.

Take your time & be patient. The car will sound better & will certainly breath better!! :cheers: :cheers:
 

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I have noticed that the burbling sound on decel has gotten louder. I'm not sure if it's because of the louder exhaust note or the fact that my car runs a bit rich.
I noticed the exact same thing on mine.....Except I cut my pups off totally.
 

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Burbles...............seem to be Decreasing with miles on my '01.......dunno why?????.
Kinda miss em'!!!!!!!!!!.....:)
 

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That scraper tool looks like a drum brake shoe adjustment tool. Of course that before self adjusting drum brakes came along! That probably explains the new job as a scraper tool.;)
 

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Wish I read this a little sooner...

You took all the wind out of my sails dehawk:(

I was going to post a poll to see how many members actually knew what that tool was. I was trying to figure a way to incorporate the age of the voter. I thought it would have been an entertaining poll.

Are some of us getting old(er) or what:-? :D

Charlie
 

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burble?

Hey , whats so bad about that burble? I love it!:D
 

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So that's what that tool is 'supposed' to be used for!! :lol: :lol: My dad gave me that tool many years ago.......I'm glad that it finally came in handy for something! :cheers: I wonder if they still make those anymore? :eek: :eek:
 

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Re: Wish I read this a little sooner...

NYCHASM said:
You took all the wind out of my sails dehawk:(

I was going to post a poll to see how many members actually knew what that tool was. I was trying to figure a way to incorporate the age of the voter. I thought it would have been an entertaining poll.

Are some of us getting old(er) or what:-? :D

Charlie

ummmmm....I have one of those in the garage. uhhhhh...it was left to me by my grandfather...yeah..that's it!!!!:)
 

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VTR, What is your thought now on this mod, now that you have had a while to evaluate it?

Chris (woosch) and I are talking that section of the exhaust down to do a clutch bleed with some fresh fluid. Looks like a good time to do it.
 

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Discussion Starter #19
gmblack3 said:
VTR, What is your thought now on this mod, now that you have had a while to evaluate it?
Chris (woosch) and I are talking that section of the exhaust down to do a clutch bleed with some fresh fluid. Looks like a good time to do it.
It's been 4 months now and several thousand miles and not a single bad side effect. If you sort through my mod list you'll notice engine mods are minimal and were done for under $800. There's no doubt in my mind that ditching the pre-cats played a major role in getting my 01 to produce 02 power levels. The nice exhaust growl alone was worth the effort.
 

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Thanks for the response! Looks like Chris and I will be gut-less after this w/e. I'll try and take some pics to add to your write-up.


VettTheRipper said:

It's been 4 months now and several thousand miles and not a single bad side effect. If you sort through my mod list you'll notice engine mods are minimal and were done for under $800. There's no doubt in my mind that ditching the pre-cats played a major role in getting my 01 to produce 02 power levels. The nice exhaust growl alone was worth the effort.
 
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