My car failed the smog check last month so I pulled the catalytic converter to see if all was well-it wasn't. The ceramic honeycomb was completely blown out of the converter. Before putting the new converter on the car, I took my air hose and shot it into one tail pipe( I taped/blocked off the other three). Nothing shot out the pipe where the converter is normally attached. So, either the ceramic honeycomb had already passed out of the tail pipe or it's clogged up in the muffler. Prior to installing the exhaust, I performed the same ritual and got quite a bit of ceramic honeycomb to "back-flush" out of the muffler (apparently the PO had a converter come apart too). So, I'm a bit worried that there's quite a bit of honey comb in there. Do any of you know if the muffler is designed such that this material will either be trapped or it will pass on though?

Yes, Tom, it can clog the muffler. My first 85 did just what yours has done. The back pressure got so bad that it blew the Oh-2 sensor out and the car would hardly pull itself. One benefit, though is that it was extremely quiet.

How did the car sound?
If it was really quiet, or down on power, the guts may be in the muffler. If it runs okay and sounds okay, I wouldn't worry too much about it.

quote Originally posted by fierofool: Yes, Tom, it can clog the muffler. My first 85 did just what yours has done. The back pressure got so bad that it blew the Oh-2 sensor out and the car would hardly pull itself. One benefit, though is that it was extremely quiet.

Hmmm? I hope it doesn't get that bad. I really don't want to wrestle those springs again. Thanks for the response!

I believe it has perforated tubes.

I don't know what to tell you.
If it still sounds and runs okay, I'd be tempted to leave it alone.

You can try banging on the muffler with your fist. If you hear it rattle, it may be full of cat innards. Or the insides may be coming loose.
FWIW, when my stock muffler finally failed on my 3.4, the inner skin (or something) started rattling against the outer skin, and made a hell of a rattle. Sounded like an airplane.

As an absolute worst case, one of two things can happen. (At this point, I think both are unlikely.)
1. The muffler will clog up, which you'll notice immediately, due to reduced sound and power.
2. Any chunks of the catalyst may continue to heat, and may burn through the muffler. (Kind of like a little Fukushima.) I've never had this happen, but I heard about it on the internet, so I have to assume that it actually happened at one time.

When my cat broke up, the car got quiet and slow. I could rev it up, and blow little chunks of catalyst out of the tailpipe. But then, I had a straight through muffler at the time. The catalyst substrate mostly got caught in the converter itself.

[This message has been edited by Raydar (edited 01-09-2012).]

quote Originally posted by Raydar: I believe it has perforated tubes. I don't know what to tell you. If it still sounds and runs okay, I'd be tempted to leave it alone. You can try banging on the muffler with your fist. If you hear it rattle, it may be full of cat innards. Or the insides may be coming loose. FWIW, when my stock muffler finally failed on my 3.4, the inner skin (or something) started rattling against the outer skin, and made a hell of a rattle. Sounded like an airplane. As an absolute worst case, one of two things can happen. (At this point, I think both are unlikely.) 1. The muffler will clog up, which you'll notice immediately, due to reduced sound and power. 2. Any chunks of the catalyst may continue to heat, and may burn through the muffler. (Kind of like a little Fukushima.) I've never had this happen, but I heard about it on the internet, so I have to assume that it actually happened at one time. When my cat broke up, the car got quiet and slow. I could rev it up, and blow little chunks of catalyst out of the tailpipe. But then, I had a straight through muffler at the time. The catalyst substrate mostly got caught in the converter itself.

Thanks Raydar. That's pretty much the line I was thinking along.

my first cat lasted about 8 years then i put on a new cat which only lasted about 300 miles. i believe the first cat clogged up my muffler cause after the second cat was installed i noticed that it didn't sound quite right and the flow out the tailpipe wasn't that strong. i banged on the muffler to see if i could hear it rattle all i heard was a thud, then i proceeded to put on a straight pipe in place of the cat to see if the muffler was really clogged. when i did this the same results, so i took down the rest of the exhaust that's when i could really hear the pieces of the cat in the muffler. it sounded like a bunch of marbles in a can. now i'm waiting on a new muffler so i put my car back together.

Try use a shop vacuum and seal the hose at cat end. carefully hit muffler and pipe to loosen cat inners.
Should help.

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