I have my y pipe out and I'm going to change my O2 sensors.

Is there any way to test the flow of the CAT?

I'm not inclined to gut the CAT or put in a straight pipe...

 

If it is clogged, you will definitely be able to tell. Take the car for a spin and when you come back it will be glowing bright red. Also, it will run like SH*T!

 

I had a solid blanket of smoke behind me when my got completely clogged

 

lets see when mine clogged i had MAYBE 100whp i could put my foot to the floor in any gear and it would take forever to accelerate, i could hear the back pressure, i thought i had actually blown the motor

 

When I've had a cat collapse, my car wouldn't rev past 1K and it had absolutely no power. The exhaust manifolds were also glowing a tad when I finally made it home.

 

Okay, thanks... Mine hasn't displayed those symptoms...

THe Cat has been rattling, but I can rev the motor and none of the exhaust has been glowing...

 

If it's rattling it could just be coming apart from being so old. Disconnect it and drop it down and shake it around if anything comes out that is your problem.

 

also check the heat shield it rattles easily and can be mistaken for a bad cat.

 

I had the y pipe out so I looked at the heat shield and it is tight...

Also I checked the honey comb inside and it appears to be intact...

I did notice that the entire honney comb has a little play inside the casing...

Just for laughs, I hooked up a 8 hp shopvac to the cat side of the y pipe and it wasn't restricting the airflow at all...

 

You could also check your tailpipes for what would appear to be metal shavings.