JoshVanWay

I was wondering how hard it was to gut a catalytic converter and if it was worth it. Looking for a nice mean sound from a TPI 305 with 80 series flowmaster cat back on it. And I was wondering what are the 4 tubes running from the catalytic converter on my 1991 Trans Am GTA???

Gramps

iTrader: (1)

that is just a ceramic chemical designed to heat up and contunue to burn unburned carbons...you can just blow that stuff out by hitting it with a hammer and a big pry bar. its like breakin up a brick.

Kevin91Z

iTrader: (1)

I dont know about four tubes. You should just have one small tube on the driver's side of the cat. That is for the air from the smog pump that heats up the cat and makes it do its job better.
Gutting the cat with a Flowmaster muffler makes it sound like crap, in my opinion. Unless the cat is already plugged up or damaged, just leave it there. Save up for a "high-flow" aftermarket cat like from Magnaflow and keep the car legal and the air clean.

IROCThe5.7L

Don't bother just gutting it if you're not going to put a pipe through it.

1991Formula350

Hello guys, I am reading this and see the clogged up cat line, I was told mine was clogged by a Pontiac engine builder when he heard how low the car sounded and how average the power is. Mine is a '91 TPI 305 Formula, is that true that the cats get clogged, mine has 40,005 miles on it as of today (original) but car was stored for years by original owner. Also, can I take the 4 bolts off cat and remove without going to a shop and how do I clean it up, PLEASE HELP, Thank you! Andy

Jetmeck

iTrader: (3)

Gutted cat here with a Flowmaster and headers.

'87 305 TPI sounds great. I have to change the factory exhaust on my 9k mile '89

A long drill bit will help save your knuckles busting the convertor material up. Drill it full of holes then beat on it and it will fall apart easily.

MARO-MAN

Spray some water in the cat and when your hammering it out you won't get all that dust in your face. Just a thought. -Nick.

Toyota h8r

I have heard of taking the cat off the car and soaking it in gas. Then the "stuff" inside almost falls out... Is there any truth there? Also, is there a cat that i can use off a 350 for my lg4.(to breath better)

five7kid

iTrader: (14)

Okay, stupid question: If you're going to all that work to ruin a cat, why don't you just remove it? A piece of straight pipe will flow better than either a gutted cat or a cat with a pipe through it.

For the highjack question about LG4's: Get headers, cat, & cat-back for '86-'90 TPI single cat application. Just a cat isn't going to help enough to justify the expense.

IROCThe5.7L

To pass the "visual" inspection. Here in Buffalo, we have a visual but no sniffer.

Jetmeck

iTrader: (3)

YEP, I get a kick out of the inspection guys who turn and look at the car when I pull in. It is a little loud...lol

They look under the hood then look under the car.
That cat in my car doesn't need nine lives it will never clog or wear out and I highly doubt it will ever rust out.

five7kid

iTrader: (14)

Awhile back, a member talked about putting the cat shields around a piece of pipe to pass visual. . .

brodyscamaro

It's so much easier, that's how I roll...

Jetmeck

iTrader: (3)

That'll work if the inspector is BLIND !

Done enough of these to know that won't fool anybody, let's be real here. If your vehicle does not get a visual inspection you'll do fine with that but if anybody looks your in trouble.

Gallileo60

The pipe thru the cat flows the same a s a straight pipe...I dont think they ever have looked under mine here in Texas...They do sniff tho, and look under the hood....

third-gen rs

i have a buddy that hollowed out his cat, and it made a huge difference in sound with the 80 series, but it would backfire as if a gun was going off

IROCThe5.7L

Where did you get yours?

five7kid

iTrader: (14)

Not quite. The OD has to be the same size at the cat inlet/outlet ID, so it is by defination smaller than a piece of straight pipe in place of the cat.

brodyscamaro

You're wrong. I don't feel like telling you why, but different quality of work yields different results...
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On my Camaro I bought a Catco cat and cut the heat shields off. They were only spot welded in 4 places. I sold the cat, and welded the heat shields around my 3" piece of pipe. It looked 100% exactly like a regular Catco converter.

On my truck I removed the converters, gutted them, and used a horizental band saw to cut the cats in half. Cut then ends off until they would fit around 3" pipe, and then welded them up. These don't look as good as my Camaro's setup, but it does its job without fail...

84L69TA

Call me crazy, but an LB9 with a Flowmaster will never sound mean no matter what you do to it. Youre not going to go any faster. I think thats how thirdgens get a bad name a lot of times...because of the stupid hillbilly stuff some people do to them

Gallileo60

Well ive seen them done where the pipe was the same size as the exhaust the cat was modded, then brazed all the way around..Unless you REALLY look carfully, you can not tell, but this way it does flow exactly the same, cuz it is the same...I hope I explained that right..lol...Tom

1991Formula350

I just had my cat removed today and put 2 1/2" pipe in it's place. Now the car runs better, but the sound is almost the same. Stock 305 here. Andy

Jetmeck

iTrader: (3)

Who do you think you are talking, an 18 year old ? Absolutely no way you'll fool anybody ESPECIALLY when they know what to look for.

brodyscamaro

I've fooled them many years in a row now

Like I said my Catco "cat" was EXACTLY like the real thing, I had those shields heli-arced.

MrDude_1

anyone else ever notice how guys with fast cars are often trying to quiet them down, while guys with slow cars are trying to make theirs louder??

Stevo

iTrader: (45)

No, cause i see plenty of "loud" "fast" cars at the drag strip all the time. Car shows its the same thing...

Maybe its just cause my car is slow.

...damn your cocky.

MrDude_1

im not just cocky, im also rude, crude, and socially unacceptable.

also, i eat babies.

rideon1200

You "EAT BABIES".
SORRY MR TYSON

Pyrice4

If I look into my cat when removed should I be able to see straight through with no obstructions or should I see packing or something?

brodyscamaro

You will see the catalysts....

crrllmich

Why hasn't anyone brought up a Hi flow cat? There like 48$ you wont loose anypower that you will even notice. Plus emissions and visual you will pass.

On top of all that your cars gonna smell like *** if you remove the cat...

Jetmeck

iTrader: (3)

The ONLY ones your fooling are the ones not looking. You know as well as I do most shops won't even look under there. If they do you are toast.
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Had thought about it but your right.......

Gramps

iTrader: (1)

what u mean smell like ***? my car doesnt smell like exhaust, it smells sweet and oily. and exhaust doesnt have a smell, thats how ppl die, this isnt propane.

firebirdjosh

iTrader: (1)

It's not hard to fool inspectors. Whatever gets the job done doesn't really matter, but the truth is any competent inspector can smell a difference- I'm not sure if that counts as visual or not. In the US there's a fine if you remove one anyway. Hi-flow cat is the only way to go IMO. And yes, a cat-less car does smell like a** (once again IMO).

crrllmich

Its not IMO it smells like crap.... burn gas and stick your face in it I am sure it smells good.

brodyscamaro

So tempted to ignore you, but whatever...

Every single time I've ever gone in for inspection or witnessed one they've bent down, laid down, or looked up to check for a converter.

Gramps

iTrader: (1)

well if you gut the cat and install the cat, or remove the cat and replace it with a straight pipe, i still dont understand how u can smell burning gas unless your exhaust tips go into the cab.

firebirdjosh

iTrader: (1)

If a tree falls in the woods, does it make a sound?

Just because you don't smell it doesn't mean other people aren't looking at you as if you were a ******.

crrllmich

Don't know about you but id like nice fresh air with the t-tops off and the windows down.

I don't get why you guys feel its such a great idea to not run a cat? Whats the advantage of not running it?

Don't tell me its for power advantage or because you want your car louder.

You would be lucky to gain 2FWHP from a hi flow cat over a test pipe.

Plus with the noise if your not running a cat you get that crappy sounding SNAP that thease third gens are known for making... just give it a break and run a cat.

Your not hurting anything.

firebirdjosh

iTrader: (1)

Some people like it, I know I've seen people post here stating that.

crrllmich

Yes but you ever notice the difference between our factory low output engines and an older true muscle car running without cats? lol thats the smell that hits the stop... its probaly just them running racing gas though lol.

camz286

I think it worth it if you have a decent exhaust, it sounds nice, its not loud until you step into it, if you looking for a cheap way to make it sound better and get alil more flow then yes it's worht it.

Gallileo60

Why do you say your car will smell bad with no cat???? Cars ran without them for years, and they did'nt smell bad...I removed my cat on my last car and could tell no difference in odor, as a matter of fact alot of time a bad cat will cause a bad odor...Tom

IROCThe5.7L

Cat or no cat, you shouldn't be smelling exhaust when your sitting at a light. Unless you have dumps or something.

Gallileo60

If you have much of a smell, your air fuel mixture is off, or you have oil burning problems....Up untill the 70's no one had even heard of a cat, and there were single, and dual exhaust set ups...As far as sound they do sound better without the cat. to me.(I have mine on for now) but that is just a matter of opinion..Tom

crrllmich

Only thing I am trying to say is hands down having the cat isn't hurting you.

92rs85berlintta

iTrader: (1)

Couldnt agree more.. Besides that I dont feel like you contributing to my lung cancer is too kool either.

rx7speed

hey I'm trying to quiet my car down does that mean I'm fast
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if it stinks when your remove the cat then something isn't right. every car I have owned hasn't had a cat on it other then the rx7 and I removed the cats on that. non of them stink like **** and of all the rx7 should as it runs rich at idle and burns some oil. well ok it does stink now but that is my own fault as I have some issues with the plugs right now

rx7speed

i chose not to run a cat cause having 3 inline cats on my little motor didn't seem to sit well. much less a car designed to burn oil which after time chances are will plug the cats up and so forth. performance difference was quite a bit. I'm still slow though but it is one less item to maintain on the car now.

Quasi-Traction

Honestly, If you want performance improvement off an otherwise stock motor:

headers, Eliminate the Factory Y pipe (more like a T-pipe), and get the appropriately sized exhaust for the velocity your heads flow and maintain a fairly equal scavaging effect. For a mostly stock form LB9 or L98 Car 2 1/2" to 3" is about right.

Keep the EGR, and Keep the cat unless its the orginal and badly clogged. The effect on performance with having both those in operable condition is virtually nonexistant.

The "popping" I would blame more on igniton, fuel or optimal tune.

also some of the materials inside catheltic convertors are worth some money to recyclers. I guess there are some really expensive Alkali Earth metals in there.