Hi all,

Over here in the UK CAT's are not required on cars made before 1992. So im thinking about removing the CAT on my 87 5.0 TPI IROC-Z and gutting it out.

So a couple of simple questions......

1, How hard is the Material inside a CAT ?? Im guessing i will need a 1" Steel bar and a big hammer ??

2, Will Gutting the CAT make the exhaust tone deeper ??. If so good as this is what i want.

3, I am assuming the improvment in gas flow will maybe produce 5hp more ??.

Many Thanks !!.

 

you dont have to remove the guts from the cat, just cut it out and replace it useing a piece of exhuast pipe and weld it shut or clamp it. it made a huge differnce on car and it sounds good for a facorty muffler, you will notice better throttle resonse and fuel milage too. although small changes in performance it is well worth it to completely remove it


here is a pic i cant figure out how to make it part of this message so let me know!

 

all i can say is that you will notice a difference in the sound of the exhaust, it will be without a doubt a deeper sound...

 

hey man , i gutted my stock cat , i wouldnt have done that if someone woulda taken it out and welded me in a piece , but that wasnt an option . So i gutted the stock cat, i just unbolted it and took the air tube out and used a hammer and steel bar, well , it didnt work , the stuff in there is like concrete. So what i did is use a big drill bit . My dad had one thats likea 1inch bit and like two feet long, i used that and it worked perfectly .

 

i supose that would work but seem like alot of trouble are cats legal where you are. ohh ya i forgot about the air tube i just cut it off and let the system vent to atmosphere wont hurt anything. i took all that crap off mine and left the air tubes on where i could not get in to cut them off. the only reason i left them on i im building another engine for the car this year.

one of my buddies lives in b.c. and he took off his cat and cut out a small piece in the top and hammered out the junk and welded it back on youll never see it from looking at it. but if you can get away without haveing one on your car you are better off with out it and just a peice of pipe welded in.

 

it will probably sound like crap, especially when you let off the gas from a rev (raaaaaasp) and it will be louder than stock... but not the "good" loud we think of. More like an annoying sound. Also, you won't notice any horsepower gains.

 

I did it, and am running with it like that cause I still am subject to visual inspections if pulled over. I took a nice long slotted screwdriver and a hammer, took about 15 min. DON'T BREATHE THE STUFF IN. Atleast go buy a cheap throw away respirator. Mine sounds good, and I welded the air tube shut, don't wanna end up with an annoying exhaust leak. Next weekend I'm gonna weld in a straight pipe, and cut off the shield, then weld it on so it looks like a cat is there. I'll tell ya if you haven't done it by then how different it is. So to answer your question, if you don't want a cat, and don't have to have it, just remove it and weld or clamp a straight pipe in there.

 

Ditto! No power gains here. I went to the track and had no better results with the cats out. Sounds just a little bit different, but barely. I wouldn't waste my time with it after having it done to my car. I have shorty headers, flow master catback, and a cut out. The cut out does better when at the track. I get some 4-5 hp with a cutout(dynoed).

 

I agree, if you don't suspect its plugged, and you're keeping the AIR, then leave it. I had to plug off my air tube anyways, so I just went for it.

 

i just welded a straight pipe where my cat was and i noticed a little of a low end power loss but it feels alittle better up top.but the weird thing was that when i looked through my cat someone had already hogged it out.

 

This might be true if you just gut the cat. I put a straight pipe through mine, and there is no snap, rasp, crackle or pop when I let off the gas. And I am running a 80 series which is kind of known for that.

 

Definite change in sound without the cat. I woudn't say it is significantly louder but more raspy. I had to put the cat back in for emmisons last year and I miss the sound the Flowmaster made when I down shifted (kinda sounded like a jake brake). Going to be putting the straight pipe back in this summer for sure.

 

If you just gut the cat, all you are going to do is introduce turbulence into the exhaust. That is bad anywhere in the exhaust system, but is especially bad that close to the motor. You want to keep the exhaust gasses flowing as fast and as hot as possible all the way out the tail pipe for a street car. If you are gonna do it, do it the right way by putting a pipe thru it.

 

^^ Exactly what he said ^^