Duntov85

Any suggestions on how to gut the cat?

apollo30346

Not that hard, kinda hard on the car, but easy with it off.... I tried it both ways and I had to take it off..... But it was a mother to get it off the pipe.... after that I took a hammer and a large flat head and banged away and would break it off into good size chunks, flip it over every now and then and do the same thing from both ends.... I ended up not putting mine bak on... I went with true dauls with LT-1 mufflers.... No Cats or Pre-cats..... Kept all my stock stuff though...... I dont' have smog down here where I live so all is cool.....Hope this helps

Silver89

Same here... hammer and chisel
:smash: :smash: :smash: :D

Kale

if you dont run a pipe through the center then the exhaust will well up in the hollow cat.

85 Dave

Why would you want to do this? The cat converter is there for a reason, to minimize emissions. If its bad, just put a replacement on it. A high flow cat doesn't affect performance, but helps keep the air clean for all who breath. :seeya

VetteRacer282

On an 85, EASY....
Unlike the guys with the 88 and 89 mentioned.... Yours is bolted front and rear (I went thought he same thing as them on my 87, except I cut and banana-peeled my cat)....

Unbolt the front, Unbolt the rear, drop it out. Get a bucket, a rubber mallet, and a good metal pipe and go to town :)
Take a couple minutes....
Unsure on the 85... my 87 the inside of the cat was two peices, so hammer around a bit, dump it upside down, etc...

Goodluck
Matt

Marcho Polo

I took mine to a muffler shop and they cut the pre-cats off and welded a tube there. My main cat was shot also, so I just bought a new y-pipe with no pre-cats and new main cat instead.

I don't know how you could do it while they are on the car, pretty much have to have them off.

TPFKATK

Mine thoughtfully committed suicide. Took it off and it was already busted up into little peices...
Harold

Kendall

After I got mine off I just used a hammer and a tire spoon and beat the brick inside into small enough pieces I could shake it out. Work at it from each end and it will all fall out. a piece of pipe could be used instead of a tire spoon. The stuff inside is just cinder like. Mine kept shifting back and blocking the exit on the Cat. I dunno if they are supposed to be loose like that or not but mine was.

vette92_1

?????????????????What the ___?????????????????

I thought the whole point of changing out stock exhaust with a "High Flow" exhaust, was for better performance. Last I checked, the cats are part of the exhaust, so if you replace those with "High Flow" it should help with performance, as long as it is higher flow than what you took off.

BobMachus

I think the point was that a high flow cat does not have a deleterious effect on performance and that it is much better for those of us with lungs to have as many cars as possible with catalytic converters.

:cheers:

vette92_1

I guess I took his quote to literal. I actually thought he ment what he said
I didn't realize he was trying to say that it wouldn't have a "negative" effect on performance.

Jeffmete

To follow up, on a '90, 6 speed, does taking the convertors off lower back pressure enough for a HP improvement? Can the ECM compensate for the lower back pressure? Is there a down side here?

Hendej

Some have reported a persistant code 32 since the EGR system needs some x amount of backpressure to function properly. Not everyone runs into this. Easily fixed in the PROM if need be - you're not going to pass emissions anyway, so why bother with EGR. Tip-in knock from lack of EGR can also be dealt with electronically.

Jeffmete

"Easily fixed with the Prom"! How does a guy in the middle of nowhere (southern Indiana) get a prom reprogrammed?

Togo

4 bolts hold the cat on, and 5or6 hold the shield on above it, you MUST remove to gut, i used an air chisel to break up the "stuff" in mine while it sat over a trash can, and to reassemble, i recommend dropping the 2 bolts that hold up the mufflers to allow an easier alignment to bolt the cat back up.
all in all, it was no more than a 2 hour job for myself!

Jeffmete

Does anybody have any documented data on what gutting a convertor does for HP? or ET"S

TA

I improved my et by about .15 with the only change being a gutted main cat. I thought it was pretty simple to do. I backed up on ramps, took off the rear y-pipe and mufflers, and used a hammer and large chisel to gut the inside. Took me about an hour and I never took the cat off the car. I then followed that up with 2.5" front and rear y-pipes (no pre-cats) and two-chamber flows and it has made a huge difference. :yesnod:

C4Dreams

I went to gut mine the other day, come to find out im to late...Someone did it for me. :-D was hollow...Whats this though about putting a pipe through it? What does this accomplish compared to just being hollow...Btw it comes off easy on an 85 well at least mine did
C4Dreams