pipe

Can you tell by looking if the cat convertor is clogged? Also what will it look like when clogged? THANKS FOR THE HELP

CFI-EFI

You should be able to see straight through the cat. If it is clogged, some or all the openings through the "honey comb" won't pass light.

RACE ON!!!

comp

i've seen new cats' i couldn't see through

jsinga

Usually if a cat is clogged bad the car just won't go, past where max airflow any more gas just won't make any difference.
Here's how I've seen them diagnosed: Pull the car out of direct sun, open the hood and hold the engine at about 2,000rpm, in about 30 sec the exhaust manifolds were glowing cherry red!
I've seen 3 like that in person. One was mine after a pre-cat brick broke up and plugged the main cat.

JS

chriswtx

We use a pressure gauge at work to check cats. We drill a small hole 1/8" in front of the cat and hold a pressure guage with a rubber hose on the end up against the hole. While having a friend rev the engine to 3000rpm or so you should not see more than about 4psi of pressure. You can use a cheap fuel pressure guage from the autoparts store that is designed for low pressure carb. fuel systems.

BigTodd

Another way is to have someone sit in the seat and rev it up to around 1500 rpm's and you go to the back of the Vette. Listen for a wheezing sound and not very much exhause volume coming out of the back of the pipe's.

You will notice a big difference in the power, (Like there is none). I had this happen during a Corvette weekend, after we had the autocross. Luckly I found a cool dude in a service station who cut out the fryed Pre cats and installed bypass tubes. We had to blow out the main cat and it actually ended up giving me a little more power once done.

BTW the 88 sound killer now with only the main cat as my only noise reducer, I had installed muffer elim's installed before this happened.

madmike

everyone get rid of your precats. My vette still passes smog with a main cat only. Precats just breakup and plug the main cat.