These have lasted the longest so far - 14 months! I'll probably have to get another set. They were Magnaflow 59959. Good thing I like 3-bolt flanges.

The driver side pipe has my wideband bung in it.


The passenger side appears to have been hotter. The inlet side is distorted and the exit side has squeezed down a lot. The rear O2 prevented the entire element from going further.




The driver side element slides back and forth inside the can. Both ends are crushed as though it were oscillating back and forth. I guess that's possible at low RPM.




So, for Friday at least, I'm running open headers with turndowns until I can drill this stuff out and remount the empty cans while I wait for new parts. I won't run it for long without catalytic converters - can't tollerate the smell and the extra noise.

 

That's unreal

 

I've seen similar cat problems when using a cam with long overlap and a minor rich condition. The Cylinder firing would flash right thru the hedders during the overlap. Basically extending the burning cycle down the hedder tube and into the cats. Usually the hedders will be really hot on the turns out of the exhaust port too. Not the best for cat efficiency, but moving them back away from the hedder will help allot.

 

I would be calling Magnaflow to see what they had to say about this...

 

glad to see im not the only one.

 

Looks like a failure from an improper tune. I have sold and installed several of those cats without any issues at all.

 

I just ordered a pair of those exact cats today.

 

This happens when your engine is running too rich.

 

I'm buying exact copies of these again. They held up well with what I've put them through. These cats have had to live with the installation of the 383, the W140AX with the intercooler, the 62lbs/injectors, and all the tuning headaches that came with these things. A lot has transpired over the last 14 months. The next set has better odds at survival.

I drove it to work, then to lunch and back, and then home today with open headers. Freeway and everything. People just look over at you like WTF when they realize everything in their rear view mirrors is a jittered blur. It's fun. I got a little video of some quick throttle stabs and idle to share. I see video like that all the time on here, but Gen-III/IV engines just don't sound like a cammed classic SBC.

https://www.performancetrucks.net/fo...d.php?t=401153

 

your cats saw alot of unburned fuel to get that bad.. ive done it before but it was my fault...