B0dyDr0pp3d

iTrader: (4)

So I'm pretty new to the whole F-body game. I bought my brothers 2000 SS just a few months ago and have put on about 4k miles since (Driving from Norcal to Socal and back a couple times). One day when I was painting my pitted chrome SS wheels I decided to chop off the SLP cat-back just to see how it would sound. It sounded pretty awesome but then I started to notice some serious power loss. I figured it was the chopping of the muffler and I didn't plan to keep it like that long so I welded it back on after only a few hundred miles. That didn't solve my problem and then I was thinking it had something to do with the clutch slipping cause it seemed like it just wouldn't hook. Then after some solid LS1tech research I read it could possibly be a clogged cat. So one day after a pretty solid 30 minute drive around town, I waited about 10 minutes after parking it and got underneath and felt the exhaust pipe after the cat.... It was cold, like it hadn't been driven in hours. I then reached up the pipe till I got to the cat and it was scorching hot. The exhaust is also extremely quite (obviously compared to it being straight piped) and even more so then when I originally bought it. The good news is that I have some FLP Longtubes and catted Y-pipe with IMCO Cat's (used but in good condition) ready to install. As far as I know I'm only missing the 02 extensions to do the header install. I wasn't sure when I was going to install it but now it seems like it has to be done sooner than later. Will driving with clogged cats harm my SS until I can find a weekend and some decent tools to install the headers?

RPM WS6

iTrader: (3)

Sometimes cats begin to melt and become clogged, usually when too much fuel has been introduced into the exhaust for one of several reasons. I'm not sure if your test of touching the pipe 10 minutes later can really be used as much of an indicator though, as the piping downstream of the cat will normally cool MUCH faster than the cat itself. Under normal conditions, it's not abnormal to see cat surface temps of 450°F+, and the cat material will hold this heat much longer than the hollow pipes beyond it. Furthermore, if the cat was clogged enough to block all/most flow on that bank, then you would have serious driveability issues beyond just a loss of power (the engine probably wouldn't even rev into mid or upper range rpms), and sometimes you can even see the cat glowing red with heat. If you have an IR gun, you can read the surface temp of the cat while the engine is running, this may help to answer the question for you.

In the end, I personally would not be 99% sure it was the cat based only on the info known so far. Power loss could be many things relating to fuel (injectors, pump) or spark (weak or lots of KR) or poor sensor data (O2s, MAF). You also mentioned the possibility of clutch slippage. The exhaust may just seem more quiet now because you had gotten used to the noise with no muffler. If you have a scanner, I would consider looking for any stored DTCs, and tracking some basic info such as O2 values and LT fuel trims, you could also look at timing and KR data. It may also need some basic tune up type maintenance, including an MAF cleaning.

B0dyDr0pp3d

iTrader: (4)

I'm not claiming I'm a rocket surgeon but I know what a normal cat back exhaust tube should feel like after a good 30 minute drive. I definitely should have mentioned that my SS threw a p0420 code a few hundred miles after driving it. But being a previous tuned F-150 owner I came across many codes that didn't mean anything once I started modding the intake and exhaust. My main concern is that this Camaro hasn't been driven more than 3,000 miles in 4 years and then when I bought it I have driven it 4,000 miles in 4 months. The clutch slippage issue I mentioned was because sometimes I'll hit it in 1st or 2nd around a corner and get a little bit of drift yet it doesn't seem to match with my RPM's and I can feel if the wheels are spinning or gripping. I'll rev it up to about 5,000 once the clutch is completely engaged and there will be a good 1 or 2 second lag before the car starts pulling, and its not slipping in between.

Thanks for the feedback, I guess I should bring down my estimate of 99.9 to about 90% but I'll post the results once I get the cats out of there.

RPM WS6

iTrader: (3)

I still think the touch test isn't really telling you anything here. If the cat was blocking enough exhaust flow to not allow the post-cat piping to heat up normally, then you would have a lot more issues that just some power loss. You mentioned revving to 5k rpm, that wouldn't even be possibile if exhaust flow was blocked that much on one, or especially both, banks. Driveability and MPG would be extremely poor if the blockage was that serious.

I had this thread in mind while doing some work on my '02 today, and after a 20 mile road test I let it sit for 10-15 minutes, then shot the cats and piping with an IR gun. The pipes just behind the cat were cool enough that I could wrap my hand around them and it felt cooler than my skin; the IR gun said 85°F....and dropped rapidly as I moved further down stream. I then shot the cats with the IR gun, and they were 200-230°F depending on where I took the reading, so as you can see they hold a lot more heat for a lot longer.

As for the P0420 code, that's pretty common on the '00-'02 cars, GM even extended the cat warranty due to this. The code just means that the catalyst material is inefficient at scrubbing the exhaust (too little oxygen storage capacity), but it doesn't necessarily mean that the cat material is melted or clogged. You would get this same code if you gutted the cats completely and didn't tune out the DTC or run O2 sims. It doesn't directly indicate reduced flow, just increased emissions. Having said that, I have a P0430 (other bank) as well, it's been there for months and I just ignore it because we don't have a sniff test here. Mine isn't showing any signs of being clogged (surface temps are the same bank to bank, no power/driveability/MPG issues at all).

How serious is the power loss? I ask because, you will feel a power gain from installing the headers no matter if the current cats are clogged or not. In other words, if the cats are not the issue, you may still be down on potential power but not notice it because of the increase in power due to the headers.

I would still take the time to do some data logging an other tests (fuel pressure, etc.) before installing the headers, if it were my car.