Removing cat 1977
Thread Starter
Melting Slicks
Joined: Jul 2010
Posts: 2,759
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
Removing cat 1977
Has anyone removed the catalytic converter from their car and what effect did it have on the exhaust sound.
Instructor
Joined: Jun 2010
Posts: 199
Likes: 0
i have a true dual exhaust and no cats and a old ratty 2in exhaust waiting to get it's upgrade to 2.5 and flowmasters but it don't sound to bad now pretty healthy. It will get a lil louder but i don't believe that much due that a cat is one big fine holed baffle.
beware if your state need the car to be the way it was for inspections (meaning cats and smog pumps) removing the cat will no longer allow that car to be inspected.
beware if your state need the car to be the way it was for inspections (meaning cats and smog pumps) removing the cat will no longer allow that car to be inspected.
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
Instructor
Joined: May 2010
Posts: 113
Likes: 0
From: Shelby Twp. Michigan
Le Mans Master
Joined: Oct 2007
Posts: 7,431
Likes: 958
From: Tennessee/Rhode Island
Get rid of the cat, true 2.5 inch duals, and if you are like most states, 25+ years, no issues with emissions testing (the typical wack job states will bust your b*lls about emissions but they are the minority by far!)
Drifting
Joined: Jun 2002
Posts: 1,590
Likes: 28
From: Tallmadge Ohio
C3 of Year Finalist (stock) 2019
St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16-'17-‘18-'19
Oldtimer
2-1/2" true duals with no cats. Stainless all the way with stainless mufflers. They have been on the car 23 years and look great.
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Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
You may need to advance your timing slightly a few degrees if you get any popping on deceleration once the test pipe is installed.
I had to do this 2 degrees base timing increase on my old CFI motor when I used a test pipe to get rid of the popping when I let off the gas. Motor ran better than ever.
I had to do this 2 degrees base timing increase on my old CFI motor when I used a test pipe to get rid of the popping when I let off the gas. Motor ran better than ever.
Burning Brakes
Joined: Feb 2009
Posts: 780
Likes: 1
From: Shelby NC
On this car I did not have a chance to run with stock exhaust. Re-did the car and used this exhaust system when it went back on the road. Engine is not a pure stock engine. I'm sure it would improve performance of any engine because of less restriction. I like it- my wife thinks it is too much noise. ?????? 
Intermediate
Joined: Dec 2009
Posts: 42
Likes: 1
From: Gayndah Queensland
BP. Regards from Downunder. When I purchased my 76 Vette it had the stock stand exhaust system with the cat under the passengers seat(Huge thing). I took it to an exhaust centre and had a complete 2 1/2 inch system fitted, deleting the cat. Instead of mounting the mufflers at the very rear of the car they mounted them just forward of the diff. One took the position of the original cat with the other on the opposite side.Makes the rear of the car look very clean, and uncluttered. Mufflers used were tri-flows. They are fairly quiet but give you that distinct V8 chevvy rumble and dont appear to upset the boys in blue.The exhaust from the mufflers back follow the original lines to the original outlet position.
Regards
Plumma
Regards
Plumma
