Im wanting to gut my cat but I dont know how to. Can someone give me some ideas? Thanks!

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1992 Camaro RS 3.1L
T5 Manual 5 speed
Cold/RAM air intake
Z-28 Exhaust
8.5mm MSD Ignition wires
TB Coolant bypass

Soon to be a 3.8L turbo RS

AIM screen name - Stopsign696

Kills:

95 (****) Probe GT,94 Mustang GT,91 CRX (dont ask me why he raced me),2nd Gen Z28 (350) haha to you V8 guys!,1992 RS 305 TBI (good race),First Gen Integra, Old Escort LX
More to come

 

stab it with a long screw driver repeatidly as if it were a mustang owner.

 

LOL, stab it where? Take it off first I hope. And then stab INSIDE it to get all that stuff out of it?

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1992 Camaro RS 3.1L
T5 Manual 5 speed
Cold/RAM air intake
Z-28 Exhaust
8.5mm MSD Ignition wires
TB Coolant bypass

Soon to be a 3.8L turbo RS

AIM screen name - Stopsign696

Kills:

95 (****) Probe GT,94 Mustang GT,91 CRX (dont ask me why he raced me),2nd Gen Z28 (350) haha to you V8 guys!,1992 RS 305 TBI (good race),First Gen Integra, Old Escort LX
More to come

 

I just partially gutted my friends cat on his S10 yesterday. Part of the stuff inside had broken up and was blocking the exit to the cat, it would only rev to 3000 floored! We unbolted the intermediate pipe from the cat and used a peice of conduit and a hammer to break up the peices. Sometimes they would get to far back in there and we would have to start the truck up and blow the debris out and that would also put the remaining peices in position so that we could attach them.

I only did half of it, the other half was intact so I left it alone. Don't know if this will help at all, but hey.

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1989 Pontiac Firebird Formula LO3 Auto
-180 degree stat
-Hooker Cat-Back
*****Possible summer '01 mods*****
Open Element, Auburn Posi, Keyless Entry, wonder Bar off the IROC, 4th gen seats, T/A tail lights

1985 Camaro IROC-Z LB9 Auto
http://www.geocities.com/krt80/

 

use a knife and a pair of gloves. tends to be bloody.

 

If you have access to a cutting torch, use it. Last year in shop, we pulled the cat off of one of the guy's trucks, blasted the inside with the torch and knocked out the leftovers with a 2" diameter steel pipe. It's quick and a lot of fun. Anything with a cutting torch is fun. It's also good therapy. Uh oh. Looks like I've been reading too much Car Craft.

 

car craft : ME
Bible : churchies

"the best modification to a 301 TA tubo engine is to replace it with a 455." HAHAHHAHAHAHAHA

 

I wouldnt do that If I were you. In fact I have done it and I can tell you from experience that it will do more harm than good. What happens is when you beat the material out there is still some of it in there that you cant get out. Since the cat conv. is now an empty chamber it causes hot exhaust gas to swirl around in the chamber which causes a lot of the crap to get back into your engine. Your exhaust flow is reduced and your back pressure is non existant. Your engine must have a certain amount of back pressure otherwise you will burn your exhaust valves. You will not gain any power by doing this. It will also make your car sound like a pickup with bad mufflers. To get the desired deep tone, you have to have back pressure. Another thing, once you break those gaskets you must replace them with new ones or you will have an exhaust leak which will make your car back fire loud!

My recomendation. Go buy an aftemarket high flow cat. They pass emmisions tests everytime and your car will sound best with a high flow cat. If you want to go cheap go to a muffler shop and have them mandrel bend you a straight pipe and get a good muffler like a Flowmaster or Borla. This way your car will have the proper back pressure, more power, and great sound.

 

I can't dissagree with you on the back pressure idea, but so long as you slide a good piece of pipe inside that cat you have no swirling crap re-entering your engine.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Gutted Catalytic Converter, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, Ported TPI Plenum and Base, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

leaky gaskets do not cause backfires,they just sound like trash, backpressure is bad (velocity is good). can we please dispell the myths here!! Listen to a recording of a guys car with a quality muffler and no cat.....they sound damn nice to me

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 226/230 duration and .477/.480 lift. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter. Edelbrock TES, 3inch cat, flowmaster with single 2.5 inch exit.
13.24@104

 

1) Most people put a pipe through it, and I don't see how the debris could get back into your engine that easy, exhaust usually flows away from the engine, not to it, the stuff might make it part of the way up the ypipe somehow but it's not going to make it all the way up into the engine.

2) So with no cat you can't get a deep tone? So 60's muscle cars don't have a deep tone, they have a trashy high pitch sound.

3) What gaskets? and backfires please, if a header leak doesn't cause backfires I don't think one after the ypipe will.

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1989 Pontiac Firebird Formula LO3 Auto
-180 degree stat
-Hooker Cat-Back
*****Possible summer '01 mods*****
Open Element, Auburn Posi, Keyless Entry, wonder Bar off the IROC, 4th gen seats, T/A tail lights

1985 Camaro IROC-Z LB9 Auto
http://www.geocities.com/krt80/

[This message has been edited by Keith5 (edited January 24, 2001).]

 

So you mean its not just gutting the cat? I have to put a pipe through it? If so whats the point of the cat!? And gaskets? WTF! I thought it was just a cat bolted or welded onto the exhaust pipe!

------------------
1992 Camaro RS 3.1L
T5 Manual 5 speed
Cold/RAM air intake
Z-28 Exhaust
8.5mm MSD Ignition wires
TB Coolant bypass

Soon to be a 3.8L turbo RS

AIM screen name - Stopsign696

Kills:

95 (****) Probe GT,94 Mustang GT,91 CRX (dont ask me why he raced me),2nd Gen Z28 (350) haha to you V8 guys!,1992 RS 305 TBI (good race),First Gen Integra, Old Escort LX
More to come

 

I think it's welded to the ypipe, at least it sure looks like it. It bolts to the I-pipe. It would be better to put a pipe through it I would think. The reason to keep the cat's case, is so the car looks legal.

Edit: had to clean up some typos.

[This message has been edited by Keith5 (edited January 24, 2001).]

 

Then why did you guys say if i gut the cat it would sound different than a straight pipe?

 

If you just gut the cat, it will have a different sound than just taking it off and putting a peice of pipe there. If you put the pipe through the middle of the cat, it should sound like whatever a peice of pipe there by it's self would sound like.

I don't know which sounds better, someone else will have to give you an opinion on that. If you want a better sound and you haven't already put an aftermarket catback on, do that and leave the cat. That should give you a better sound. If your car is high mileage, and the cat is starting to clog up, that would be a good time to put a new high flow cat on, or just gutting the old one like said before in this thread.

 

What we did on my brothers IROC was take the cat completely off punch out all the ceramic screens with a long screw driver. Then took the cat to a welding shop where he put a straight pipe insert in and welded it. This was to reduce the turbulance caused by cats shape. The car did sound meaner when he got on it but when be backed off it sounded like a dump truck from all of the bach firing and gurgling the car was doing. I would just go with the hi flow cat it has a more tuned sound. Plus you won't have to deal with the black carbon $hit getting on your car.
MeanTA

 

Was it backfiring or was it just racking off?

A backfire is very very loud, and sounds like a gun shot.

 

Keith5

A leaky exhaust gasket will cause your car to backfire. There is un burned fuel in your exhaust and it is very hot. When you stomp on the gas pedal you are putting positive pressure in the exhaust system. When you let off on the gas pedal that bad seal in your exhaust pipe will suck in cold air and the unburned fuel will ignite. This doesent happen with headers because the pipes are smaller and the pressure is much higher since it is next to the cylinder heads.

Exhaust tone preferences are simply that. Preferances. If you want it loud and deep, dump the cat. If you want it deep and not loud, get a high flow cat.

Vortecfcar

You are an idiot!

[This message has been edited by T/A Man (edited January 26, 2001).]

 

Man that don't cause any backfiring. Unless you have a miss or are way out of time. Man the only gaskets i know of is where the exhaust bolts to the exhaust manifolds. T/A man you are an idiot. And by the way learn to spell "preferences" correctly.

 

Now calm down children. Play nice

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--Steve S--
1984 Trans Am 305 LG4, 5 speed
RPO codes point to Recaro version
Daily Driver, Flowmaster 80 Series

 

I just gutted the cats on my Z and god what a diferance. this is what i did, i got my car up on a lift (my buddy has a big garage and is pretty rich to) then i took a air cut off tool and cut the heat sheild off then cut off half the bottom of the cat so i could pry it down then the fun part a hammer and a pry bar to tak all the crap out. After that i welded a seem all the way around, welded the shields up and took it to the track. the car picked up from a 13.85 with a 1.89 60' to a 13.71 with a 1.84 60' screw this pipe crap and high flow cats are too expensive. If any one thing cats dont cost horsepower i have the numbers right here.

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91 Z-28 L-98 Black stock 14.20 @ 97

 

Damn it, today I went to see if I could use this guys lift and I was gonna pay him 20 bucks to gut it and his manager wouldnt let him, he was scared someone would see them doing it. WTF, even if a cop DID see them doing it he wouldnt know what he was doing. DAMN, now I gotta wait till next weekend to get it done. ****!

 

The best thing to do it unbolt it, hammer an exact length piece of pipe into it, poke stuff inside of the pipe out with a stick and bolt it back up.

[This message has been edited by bullfrawg (edited January 27, 2001).]

 

So, is it worth puching the cat or is it a no-no?

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It's all fun and games 'till someone looses an eye....then it's fun you can't see!!
-------------------------
1987 Pontiac Trans Am
-305 cid motor
-700-R4 Transmission
-K&N Air Filter
-Flowmaster 40 series
Muffler
-Yokohama Tires
-GTA Rims
-3" Exhaust Tips
-180 degree Thermostat
-2.73 Posi Rear End
-JVC Head Unit w/ Kicker subs!
-And a COOL LOOKING Flowmaster sticker on the dash!
WOO-HOO!!
*Long live the F-Body!*

 

Look here ****sucker, Ive had leaky exhaust problems on many cars all throughout the system and if the car is running fine it wont backfire. If it has a combination of a burned exhaust valve, retarded timing, or is missing then I could see a backfire. Leaky exhausts do not cause backfires!

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 226/230 duration and .477/.480 lift. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter. Edelbrock TES, 3inch cat, flowmaster with single 2.5 inch exit.
13.24@104

[This message has been edited by vortecfcar (edited January 28, 2001).]

 

Guys Guys, why not just burn it off with a torch and replace it with a steel pipe? Thats what I did. Had a muffler shop burn it off and weld in a 3" straight pipe.

BTW: Not every muffler shop will do this, but where I am from, the people at this one are really cool guys and they work on a lot of performance cars so they know how it is. How do u like my photoshop editing? LoL.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

hey 91Bird305, how does your car sound without the cat?

 

Well I did the Headers and The Cat at the same time. It sound A LOT louder now with the headers and w/o the cat. Not to loud where it drowns out ur radio but it has an awesome rumble to it and when u hit 2500+ rpm's is when it gets really loud. I like it a lot.

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Eric Natzke
91 Firebird 305 TBI
"It Ain't Stock"
http://members.aol.com/j007golden/91firebird.html
For info on certain parts or mods go to the site below
http://members.aol.com/j007golden/modeval.html

 

This thread cracks me up. Search the board and see what you find. 90% of the people on this sight are idiots, these cars attract them. For every question, there's an incorrect answer. Sorting thru them is half the fun of asking a question here.

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Drew
The lone Thirdgenner of the Apocalypse
predatorman@hotmail.com
My Website
87 Iroc
91 Formula 14.3@98mph
91 RS Convertible
91 Firebird V6
92 S10
98 Grand Am GT

 

Ok people, listen up.

I'm not getting into the tree-hugger arguement.

I gutted my cat, I'd do it again, and I always reccomend it if you can get away with it come inspection.

The sound with a stock muffler is louder, deeper and crackly.

You can listen to my exhaust here: http://www.nethirdgen.org/mac/91camaro

I cut the cat off the car, used various objects to beat the contents out, a 2" steel rod is ideal.

I then used a connector and bolted the cat back on. The green arrows are where I cut the cat off.



I had to remove two "rings" of pipe from the inside of the cat where I cut it off, after that it was all cake. The hardest part actually was gutting the cat, that **** is HARD.

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Shane McConnell
macgyver@nethirdgen.org [*]Webmaster of www.NEThirdgen.org[*]1991 RS 305 T5 15.6@88[*]1979 Z28 ZZ4/2004R (In the future.)
I'm the kinda guy you bring home to Mother.

 

WOW Macgyver love your car! And it sounds mean as hell too! Woah, Im gutting my cat first chance I get!

 

And all that swirling backpressure crap is just that. That kinda stuff only matters on full-tilt-boogie cars.

I gained TQ and HP gutting my cat. Guaged on my *** -dyno.

 

MacGyver--Are your cats hollow or is there a pipe in them?

Your car sounds dam good!!!

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--Steve S--
1984 Trans Am 305 LG4, 5 speed
RPO codes point to Recaro version
Daily Driver, Flowmaster 80 Series

 

There is no pipe in the cat, after I gutted it, I found that fitting a pipe inside the cat wouldn't be worth my time. I was DEAD tired from going buck-wild on the insides, I just threw it back on.

Please remember, the stock muffler accented the crackly sound with a gutted cat, the mp3 on my website has the crackle edited out.

Adding the Edelbrock made a WORLD or difference, that MP3 is not edited.

 

I just reread that. The smog pump injects fresh air into the maifold, why would it not cause backfires?

[This message has been edited by Keith5 (edited January 30, 2001).]

 

OK Everyone, Stop beating me up about saying that an exhaust leak can cause a backfire.

Let me correct my words.

It can cause a backfire. It also can depend on the car. I had this problem after I gutted the Cat out of my 91 5.0 Saleen Mustang. (I know you dont want to hear about Mustangs here and I am probably going to get nailed for even mentioning this. I no longer have this car nor will I ever own another Mustang.)

Anyway I didnt replace the gasket and it was in bad shape and my car backfired really bad. I took it into a reputable muffler shop and he made me a straight pipe to replace the empty cat converter and sealed the leak with a new gasket and after that the car didn't backfire.

VortecFcar - I appologize for calling you an idiot.

 

hey just wondering i gutted my cat and mine didnt get any louder !!! i have a 2 chamber flowmaster on it and its toooooodamn quiet if i put strait pipe in place of the cat will it get any louder you think??? need positive feedback. please help!!!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 160 (882) heads,.447/.447 lift 222@.050 duration speed pro 327/350hp cam 350 .40 over (356) Edlebrock torker2 and a 600 edlebrock manual choke (1405)

Future mods performer rpm air gap intake (polished) comp roller cam, and way better headsa 400 defintely in the works!

 

Replace the I pipe with a bigger one.

[This message has been edited by Keith5 (edited February 04, 2001).]

 

quote:
--------------------------------------------------------------------------------
Originally posted by Keith5:

I just reread that. The smog pump injects fresh air into the maifold, why would it not cause backfires?
[This message has been edited by Keith5 (edited January 30, 2001).]


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Actually it WILL cause a backfire, thats why theres a vavle that blows the air pump pressure off to atmosphere when you suddenly let off the gas pedal. (decel)

 

actually joel that diverter valve is there to prevent the cat from overheating on decel when there is a very lean condition in the cat which could otherwise cause it to melt. Nothing to do with backfiring

 

Macgyver: What did you use to record the exaust sounds of your car? It sounds really good. And the gutted cat sounds really good!!! Do you have a single cat or a dual cats? I have dual, and was wondering if the same results could be expected.



[This message has been edited by goosejg73 (edited February 06, 2001).]

 

I have a single 2.25" cat. Edelbrock 3" cat-back.


I used a Yamaha 4-track tape recorder and a Shure SM57 microphone for the recordings

 

I'm not sure about how, but I know that when I cut off my cats and replaced them with flex tubing, my car would backfire really bad when I let off the hrottle too quickly and sometimes you could see fire inside the exhaust tips. I had my gutted cats welded back up and have had no backfires since.

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1990 Firebird Formula 350 speed density TPI; K&N, air foil, throttlebody coolant bypass, underdrive pullies, MSD 6AL, MSD HEI coil, 8.8mm wires, adjustable fuel pressure regulator, Hypertech Thermomaster chip, 160* thermostat, fan switch, B&M stage 2 shift kit, Edelbrock 1&5/8 headers, gutted dual cats, Flowmaster 80 series muffler, 3.73 posi rear end