VETJET

I am going to modify my stock exhaust on my 1981, bu tI am curious what the sound difference and performance difference would be on the car if I only remove the cat converter. Does anyone have any description of what it will sound like and what it might do for performance?

Thanks,

VETJET

Twin_Turbo

it will sound a lot louder without the cat and it will give a small perf. gain (a larger one if the cat is clogged)

If you replace the cat w/ a pipe it will sound pretty good, hollow the cat and you've got tin can alley.

Glensgages

(not Corvette-related, but...)

I bought a new Z28 in October of '78 (an early '79 model). In mid-'80, I replaced the y-pipe/cat/y-pipe with 2 'straight-pipes' into the OEM resonators ('79 muffler-speak).
It sounded moderately better at part-throttle, but at WFO,.....!!!!!!!!!!!!!!!!

In '90, we built the current 400HP 355", but I had to drive it to the strip. Curiously, it sounded no better (or 'LOUDER', depending on your preference...) with the 12-second motor than it did with the previous 14-second motor, OR the bone-stock LM-1
With 'open-headers', tho, it was a different story.....
:thumbs: :chevy :thumbs: :chevy :thumbs:

pillowmeto

If i pulled the cat, hollwed it, and put it back on would it be like as if i had put a pipe in? Also to put it back on do i need new seals, gaskets, i havent done much exhaust work so i dont rember if they are reuseable.

MAtt

79Corvette02

If you gutted the cat, it would more or less like it was hollow-but many people just run a length of exhaust tubing through the whole cat-that way the exhaust gas doesn't expand in the newly hollowed cat and create uncecessary backpressure. Do Like I did, ditch 'em, and run straight pipes! :D

Desertdawg

I hollowed mine out, and did not run a pipe through it, I also added Borla mufflers.
Mine does not sounds tinny or hollow now, but I think the new mufflers helped with this.

Performance gain was negligible.

Fang S-289

I recently removed mine altogether and installed the MAD chambered pipe exhaust. It is loud with some resonance. I haven't decided if its too loud yet.

:yesnod:

Wrecked82

So why do it?

pillowmeto

I have a 76 L48 and it has flow master from the PO. I dont wanna spend any money oo much time because i have bigger future plans. Ive got a 350hp cam thats about to go in and i was just wondering will it sound better or worse with the flowmasters if i hollwed it out or not, i wouldt run a pipe instead or run a pipe throguh it, just hollow it. So should I or should I now hollow it, also can i reuse the seals or do i need new ones.

MAtt

DTbull

MUCH LOUDER!

Chuck Harmon

I ran with a hollowed out cat on my 85. There was a bit of echo chamber sound to it underneath the passenger seat where the cat is supposed to be. Yes it was a bit louder and less back pressure. I kinda liked the sound, it grew on me.

Chuck

Desertdawg

It was starting to crumble, plus it is an easy 10 pound weight loss...

BSeery

Also, cars have burnt to the ground due to fault converters. If the mixture is too rich the converter can plug up with gas and vapors. Add some heat and a 350 cubic inch air pump blowing hot air into it and giving pressure and you can catch a converter on fire.

Richard Cooper

VETJET,
I removed the cat from my 81 last year. It sounds MUCH better without the cat. I'm not sure if I got more power from the removal because I really don't beat on the car, its got 136,000 miles and needs a motor.
I got a test pipe from MufflerTech.com and it fit perfect. They are in California. The pipe cost $32.00 including shipping. Took 15 minutes to install. I put the cat back in for inspection and then take it right out after inspection. :steering:

pillowmeto

Sounds good, i think my car has the orgional cat, 76, and orgional exhaust pipes, but they are atleast 10-15 years old at minimum. Plus i think im running a bit rich. There fore my cat has got to be clogged a bit and i wouldnt want that fire to happen, plus its over 25 yrs old and registered as a historic vehicle. My suffing coming out next time i go home, thanksgiving. Along with the addition of sway bars camshaft and maybe something else. Its going to have one hell of a choppy idle, im pushing the limits of the L48, 272.

MAtt

Fevre

I can vouch for that, I have a hollowed out 3" cat on my Formula and it is way load at all rpm's. :eek: