Hollowing out a cat converter?

[UOFLcards]

Ok. The cat on my GP is pretty backed up and I have heard that you can hollow out the cat with a steel pipe or something. Anyone ever done this? Does it give it more sound and performance?

Here's what I found on this:

http://performanceolds307.tripod.com/id12.html


Can doing this cause any problems to my engine or fuel system?

 

[CHRIS.O]

Louder yes, more performance? Probably not anymore than if it was a brand new cat. How do you know its plugged? Do you have inspection? If not just cut it out and put a piece of pipe in. Breaking the insides out and removing it all is close to impossible. You would end up having chunks of crap floating around and caught in the rest of the cat that would end up rattling I bet. If no inspection then just put a pipe in, easier that way, cats are tough.

 

[307 Regal]

I can back up the claim on increase in noise. I went from a stock muffler to a flowmaster 80 series and the sound didn't change at all until I took the cat off. Now yes, it did make a world of difference as far as sound, but not performance. Nothing you can notice anyway. Instead of "gutting it" I would suggest eliminating it or finding a high flow cat if a converter is required in your area.

 

[UOFLcards]

They do not do emissions test in my area. It is illegal to remove the cat though. Thing is I just don't want a fine for taking the thing off if a cop pulls me over and says my exhaust is too loud, then checks for my cat. Heard the fine is over $400 from some research on the net. But all in all, what is the likely hood that I get pulled over for a loud exhaust and a cop searches under my car for a cat converter? I don't think it's very likely. But that's just me.

As for putting on a new cat. How about this one? Is this the high flow kind you was talking about or would this muffle the sound down quite a bit?

http://www.jcwhitney.com/universal-cata ... id=3387991

 

[moose]

Louder yes, more performance? Probably not anymore than if it was a brand new cat. How do you know its plugged? Do you have inspection? If not just cut it out and put a piece of pipe in. Breaking the insides out and removing it all is close to impossible. You would end up having chunks of crap floating around and caught in the rest of the cat that would end up rattling I bet. If no inspection then just put a pipe in, easier that way, cats are tough.

I hollowed mine on an '85 Cutlass no problem, it was clogged bad. Symptoms were drastic change in fuel effeciency, poor acceleration, and sounds of misfiring (not sure what the sounds were exactly, but I know they were caused by exhaust gases not going through the cat and being pushed back into the engine). Also, when you remove the cat and shake it you can hear rattling because the material is deteriorated. Louder...a little, I had a stock 307. More performance...a little, nothing to brag about. But since the exhaust didn't have to force it's way through the metal filters it increased the flow of gases.

No emmisions test here, but a cat is required. I used a short handle sledge hammer and a long straight 18" chisel I picked up at Harbor Freight for around $8. Just unbolt the thing and start breaking up all the crap. I found that once I had broken through a layer, twisting the chisel like a drill and moving it back and forth while pushing down broke up the crap faster. Make sure your next to a large trash can in a well ventilated area and it would be wise to wear a mask. That stuff breaks up into a powder and will go everywhere if your not carefull when you dump it into the trash.

Most importantly, make sure ALL of the material is gone so it doesn't get sucked into your engine. Scape the inside walls thoroughly and blow it out real good with an air compressor. After that I spayed and wiped down the inside as much as possible with break cleaner. Then I drenched the inside with probably half a can of brake cleaner and stood it up on end to dry. It wasn't hard but it did take some effort and time.

 

[307 Regal]

They do not do emissions test in my area. It is illegal to remove the cat though. Thing is I just don't want a fine for taking the thing off if a cop pulls me over and says my exhaust is too loud, then checks for my cat. Heard the fine is over $400 from some research on the net. But all in all, what is the likely hood that I get pulled over for a loud exhaust and a cop searches under my car for a cat converter? I don't think it's very likely. But that's just me.

As for putting on a new cat. How about this one? Is this the high flow kind you was talking about or would this muffle the sound down quite a bit?

http://www.jcwhitney.com/universal-cata ... id=3387991

By the description it sounds like it would flow alright but I don't know about how it would effect noise. Like I said, I just took the thing off and never bought a replacement, but here's where I was shopping for them when I was still considering buying one: http://www.summitracing.com/search/Depa ... s=Rank|Asc

 

[CHRIS.O]

If you do not need to have it then I wouldnt. They dont help anything. Not being a smart *ss but do you really think a cop is gonna crawl under your car and inspect for a cat, and that he may actually know what one looks like? I am sure it has happened before but seems pretty uncommon. Not having a cat isnt going to make your car way louder. You might like it with no cat and stock muffler.

 

[megaladon6]

the best way to do it is to cut an access hole in the cat, then remove the guts. then weld the panel back in. it is best to weld in a pipe so the air flow is not disturbed by changes in diameter. if you use a long chisel, you have loose material, and an irregular path for airflow--this creates turbulence and lowers power.

 

[Minion1186]

I would take the cat off and gut it. I did this when my 86 cutlass had the 307 and single exhaust, i hollowed it out with a crow bar and made sure all the pieces where out before reinstallation.It was a little louder with my cherrybomb glasspack that replaced the muffler also.

 

[Black Sheep]

Around here, they pay good money for convertors at the scrapyard :wink: