Hello,

I just bought a stock cat for smog purposes. I plan to keep it stored in a closet and installing it only for smog day. My question is, when I pick up the cat and swing it back and forth, I get a light clunking noise. Not really a rattle, but a clunk for every 2 shakes.(a stupid sounding explanation i know). Is my cat blown? Or is it the heat shielding?

 

You should be able to see if the insides of the cat converter are melted or breaking apart by shining a flashlight and looking inside. If you don't trust your eyes but you do have an air compressor or shop vac, try blowing some air through the converter (both forward and backward) to see how it goes. Maybe add some masking tape and cardboard to encourage the air to go through the converter instead of back out around the nozzle.

 

It’s possible the heat shield is making a noise, but if you can hear a clunk that’s not a good sign. Try to see if any material comes out of either end after you shake it a bit. No material of any kind should fall out.

if you can find someone with a boroscope you could check for certain.

 

Yeah you should be able to see enough in there to see if the honeycomb inside is intact.

Dale