taking cats off

[speedster101]

hey guys ive got a 91 xlt 4.0 with a kkm air filter and and a flowmaster 40 series muffler. i am trying to get some cheap horse power and was wondering if it would be a dumb idea to take off the catts. i heard that since they're 17 years old that theyre probably not working or there clogged. the exhaust kinda smells so i don't think it would smell too much more.

I also know that i don't have to go to emissions any more since its earlier than a
95 so i shouldn't have any legal problems in IL. right?

 

[section525]

Its against Federal Law to remove your cats. If IL is in the U.S., then its illegal.

 

[fixxxer]

Mine is the factory CAT and I've passed emissions everytime here in Colorado. (knock on wood) If you're getting a "rotten egg" smell, it's probably time to have the CAT replaced.
Section525 is very much right, it's against Federal law to tamper with, disable or remove pollution control devices.

 

[LBarr2002]

Not only is it illegal, the 4.0 needs some backpressure in the exhaust system or you loose alot of torque. I've never run mine without a cat, but I have driven it a short distance with the exhaust unhooked from the cat back and it was horrible. Would not spin on dirt.

Crank the truck and put your hand in front of the tailpipe. If you can feel individual pulses of exhaust, your cat is not plugged and leave it alone. If you feel a constant flow instead of pulses, something in the exhaust is plugged, most likely the cat. At that point its up to you either to replace it (with a highflow unit), take it out, or knock all the internals out of it and put it back so it looks like there's a real cat there .

 

[aldive]

You will neither gain RWHP or gas mileage by removing the cat(s).

As previously mentioned, its illegal.

 

[speedster101]

k thanks guys.. ill probably consider replaceing them... do u guys know what kind of improvements ill have with high flows?

 

[Michiganbear]

I agree and disagree with the legality of removing the cats..

if the vehicle is to be driven on the road, ANY public road, then it is illegal to remove them (except to replace with new ones!)

if the vehicle is 'off-road only' (ie, trailered everywhere, or lives it life on a farm, never to see the roads), then it IS legal to remove any and all emissions devices. That does NOT mean your vehicle will run better without them, just that it is legal to remove them. some devices are required for our modern fuel injected engines to run right.

 

[aldive]

k thanks guys.. ill probably consider replaceing them... do u guys know what kind of improvements ill have with high flows?

None.

 

[jtb1689]

Just a deeper throatier sound depending on what you get. Other than that, all aftermarket cats (at least for our 1st gen ex's, I haven't looked into other cars) have no difference from OEM cats besides a different sound.

 

[speedster101]

do u guys know of a place where i can get some in expensive cats? the only ones ive found are the ones on autozone and theyre around $250.

 

[Michiganbear]

try rockauto.com

they list walker's at about 219 +shipping.

probably not gonna get a lot better than that for new

 

[Willard]

Look at eBay. Not gonna be the highest quality cats, but they are cheap on there, and probably good enough for your rig.

 

[energie]

haha why is everyone so against it?
i did this on my mustang, got an offroad h-pipe, now a mustang gt is different than explorer, but still.

 

[HahnsB2]

haha why is everyone so against it?
i did this on my mustang, got an offroad h-pipe, now a mustang gt is different than explorer, but still.

Because there is no need for it and it runs dirtier! I've never noticed any difference running without a cat or gutted cat other than sound. I have a single aftermarket cat on my B2, sounds good and pulls great emission numbers, it was $50...

 

[IZwack]

haha why is everyone so against it?.

Cauz its kinda irresponsible

 

[energie]

well on a suv im sure its different than on a 'performance' car.

 

[speedster101]

do i have to buy oem cats or can i buy one of those single cats and clamp it on?

 

[Four0Sport]

you can buy a universal cat but with the oval flange connecting the stock cat to the down pipe you will need to be creative with how you connect it to your exhaust.

 

[speedster101]

do i have to recreate that floating system where its spring loaded or can i just weld it or use u clamp

 

[Blacksheep Josh]

Just get it on there! Lol, I don't think it matters. If you have inspections, they'll most likely just look to make sure it's there and secure.