calys968

I'm planning on taking off my cats and gutting them but I don't think that I'll be able to get it done in one day. So my stupid question is, what would happen if I drove my car with the cats off for a day? My exhaust system is stock except for the muffler.

blkZ28spt

My advice: Leave the cats where they are. Your restriction is the muffler. Grab a cat-back, replacement muffler or cutout.
If you do drive around without cats, you'll be fine. It will throw an engine light without the cats unless you ahve it tuned out or use O2 sims though.

99Hawk262

iTrader: (19)

Get a nice set of earplugs.....LOUD is an understatement!

calys968

Thanks for your response. The only reason I'm messing with them at all is because the passenger side cat is making a horrible rattling noise.
I think they might be gutted already because ever since I got my car it's had Catalyist System Effiency Below Threshold codes for both banks and even when the muffler was stock it was way louder than my 1999 Z28 was.

So it won't hurt anything to drive for a day or two with my cats unbolted? What would I do with the O2 sensors?

Thanks again!

99Hawk262

iTrader: (19)

I would reccommend o2 simulators so you can avoid throwing codes. They are cheap. Otherwise, just unscrew the sensors and use electrical tape to protect the plugs until you put them back in. And no, it won't hurt anything to drive open for a few days. You might want to stay out of the throttle because you WILL draw a lot of attention.

calys968

Thanks for responding. If I gut my cats and I don't get O2 simulators what codes would show up? The catalyist system below effiency one?
Do you have any tips for removing the cats? Some of those bolts look like they'll be a real bitch to get out.

99Hawk262

iTrader: (19)

I don't know what codes will trip. Never dealt with that. Yes, the bolts will be a PITA. When I installed my headers, I broke all but one of them. If you were installing LT's this would not be an issue. Actually, once they break it is much easier to remove the cats. However, in your case, you might have issues. You can hope they don't break, which they will; you can hope to remove the broken bolts with vice grips afterwards, but access will be a bitch. I'm not sure this is a really good idea after thinking about it. You might think about finding someone who can weld and just cut the bottoms of the cats off, rip out the innerds, then weld the cut out section back in. But then again, the driver side would once again give horrible access. Gosh, you're in a fine dilemma. Anyone else have any ideas??? Depending on your smog laws, maybe just remove the cats altogether and get sections welded in to fill the gap. None of these are great ideas, but you don't have a lot of options. Of course, if your wallet permits, you could buy an SLP Y-pipe. They aren't horribly expensive. I guess a lot depends on what your future mods entail. Are LT's a possibility? I'm sorry for rambling, just wanted to include you in my thought process. I really don't know what to tell you. Hopefully someone else will respond with a simple fix.

blkZ28spt

I'd have to vote on replacing the cats with a straight section of pipe. If your exhaust looks anything like mine did...yikes. Had to break everything off, and it was a PITA. How old is it? The cats might still be covered by warranty. I would vote against O2 sims. Too many people have theirs go out. One of mine was bad from the start, replaced it and it went out in less than a year. Not worth the money if you ask me, unless you absolutely can't get somebody to tune the code away.

The old man

iTrader: (1)

Checked your page.... Your cats are still under warranty if you have less than 80,000 miles.

calys968

Thanks everybody for replying.
My car has 88,000 miles so unfortunantly my cats are no longer covered under warranty.
I'll probably just have the cats replaced with straight pipe. I'd like to get some LT headers but right now I can't afford them. I live in California but my car is registered in Arizona so I don't have to worry about smog. Does anybody know if I got pulled over could I still get a ticket for having no cats even though my car isn't registered in CA?

What's the longest I could drive my car with the cats unbolted without harming anything?
Somebody told me that my car will run really rich because of the O2 sensors not being plugged in. Is that true?
Thanks again everybody

blkZ28spt

Not having the rear 02's plugged in will not effect performance at all. I dont know how close the first pair of 02's are to the end of the manifold when stock, but you could run rich if you let outside air get onto the o2's. This is okay for a short while at least, I once drove open LT headers for three weeks. Once you get the exhaust sealed back up the only problem you'll have is staring at the SES light, and not knowing if another code trips the light while you are already staring at it.

99trickin

99hawk262 has the right idea.find somebody who can cut and weld,have them cut behind the cat,then use a metal rod and a hammer or mallet to chisel away the honeycomb inside.when you are done turn the car on an dgive a few revs to blow away any remainig particles and dust. then just weld the pipes back up.

calys968

My boyfriend says that if I drive with my cats not bolted on that my car will overheat because all the heat from the exhaust will be going back up into my engine bay. Is that correct?

blkZ28spt

Nope. I, and many others have driven cars with open headers/manifolds plenty. The exhaust will actually have even less resistance than if the cats were there.

calys968

Took off the cats and HOLY CRAP my car is loud! I used a lot of rust eater on the bolts and only 1 broke. My cats are already gutted so I guess I'll just throw them back on there tomorrow. And I found out the rattling noise was my heat shield, not the cat.
How loud will my car be with a cut-out on compared to how loud it is right now?

blkZ28spt

Cats do a pretty good job of muffling the exhaust just enough and cutting the rasp. If you are running open manifolds it wno't be that loud with a cutout after the cats but before the muffler.

SiRgReg23

ummm use a impact gun break those bolts loose really quick and shouldnt break any bolts thats what i did then take the cats off and send them on a nice dinner date with a tire iron then put them back on .... i wouldnt reccomend open stock manifolds .. some people dont even reccomend open long tubes not just cause it will be loud as hell but u could possibly burn a valve

calys968

Ok, a couple more questions...
I thought that having my O2 sensors not being screwed in would cause my car to run way rich, however my LTFTs are at 25%. What's up with that?
Also I saw that somone mentioned I could burn up a valve driving around with open manifolds. How big of a possibility is that?

bigchedd

I'm running a 2002 Z28, I had my cats cut-out and replaced with straight pipe today. I was throwing a code about my cats failing but when they were replace the code went away. And yes my O2 sensors are still connected. So far so good, and yes the car is loud as hell. I'm contemplating putting a LM2 muffler in place of my LM1.