97 LT1: will hollowed cats cause any issues?

**Zapper2003** · 01-25-2007, 05:05 PM

I've got the 97 Firebird, a4 LT1 yadda yadda. I plan to get a Dynomax catback system, and I'm wondering if it would be worth my while to take the cats off and hollow them out (not entirely remove them). Will doing so cause any issues (SES light, etc), or would it just be wiser to get rid of them all together?

**BlackLT1Z28** · 01-25-2007, 07:23 PM

It shouldn't cause any problems, except you might not pass the sniff test. If you have emissions, then I suggest keeping the cats entirely entact or go high-flow cats. But if you don't have emissions, but visual inspection, then gut them and keep them on the car. If you don't have emissions or inspection, then you can completely remove the cats if you want. Its your call.

**{FzS}BlacKMagicK** · 01-25-2007, 10:18 PM

Hey Black, on a Borla cat back, if I remove the cats, will it get significantly louder?

There high flow cats as far as I know (i didn't put them on) the guy who did lived in Illinois, so I guess they have emissions inspections there, but here in Fla. they don't. But I don't know if it'll make it sound shitty, or incredibly loud.

Also the guy who had them installed didn't know anyhting about the adustable plates...do all Borla cat back systems come with adjustable plates, and if so, are they built into the exhaust itself? or would you just get under there loosen something, turn something then tighten back up?
Where are they located on the system?

**5.0THIS** · 01-26-2007, 02:13 AM

Yes, you will get an SES light if you gut the cats. O2 simulators can prevent that. Yes it will make the car louder. Yes it will make the exhaust sound more hollow. No it will not hardly gain you any power whatsoever, and your exhaust will smell bad.

**BlackLT1Z28** · 01-26-2007, 08:05 AM

Originally Posted by {FzS}BlacKMagicK

Hey Black, on a Borla cat back, if I remove the cats, will it get significantly louder?

There high flow cats as far as I know (i didn't put them on) the guy who did lived in Illinois, so I guess they have emissions inspections there, but here in Fla. they don't. But I don't know if it'll make it sound shitty, or incredibly loud.

Also the guy who had them installed didn't know anyhting about the adustable plates...do all Borla cat back systems come with adjustable plates, and if so, are they built into the exhaust itself? or would you just get under there loosen something, turn something then tighten back up?
Where are they located on the system?

It will get a tad louder. I don't think the increase is major, but it will affect the exhaust note a little bit.
Do you have a small y-pipe right before the muffler and the passenger-side exhaust pipe? If so, then I think your system has the plates. I personally don't have borla, but you do to change the plates is loosen a few screws, remove one plate and then insert the one that you want to run, the button everything back up. Here's a pic of a system with the small y-junction that I was talking about.

That small flange on the passenger-side pipe is where the plates go.

**BlackLT1Z28** · 01-26-2007, 08:07 AM

Originally Posted by 5.0THIS

Yes, you will get an SES light if you gut the cats. O2 simulators can prevent that. Yes it will make the car louder. Yes it will make the exhaust sound more hollow. No it will not hardly gain you any power whatsoever, and your exhaust will smell bad.

Oh yeah, good call. I forgot that they also had rear O2's in the later LT1's. I usually just associate the rear O2's with LS1's and later. Oops.

**Zapper2003** · 01-26-2007, 02:12 PM

Well, if it doesn't Net that much gain, and this is by no means a racecar, i won't bother with them. No harm done regardless.

Is the dynomax catback an actual catback, or just a replacement muffler/tailpipes?

**BlackLT1Z28** · 01-26-2007, 05:07 PM

By the name, I'd say its an actual catback. Look it up if you want.

**Zapper2003** · 01-26-2007, 06:36 PM

I have, but the pictures show now intermediate pipe, and i've not seen anywhere in the description any mention of one.

**9t8z28** · 01-27-2007, 08:50 AM

I passed emissions with no cats on my LT1. It went right through. It gained quite a bit of power.

**Raoul-Duke** · 01-27-2007, 08:54 AM

Originally Posted by 9t8z28

I passed emissions with no cats on my LT1. It went right through. It gained quite a bit of power.

prob cause it was obd2

**Zapper2003** · 01-27-2007, 12:36 PM

Yeah, no emissions where i'm at either, but i'm gonna keep them so i don't have to buy sims.

**Schweet97Z** · 01-29-2007, 05:33 PM

if you dont want to buy sims, get a pcmforless tune and kill two birds with one stone. brian can tune the rear o2's out...

**Motormanh20** · 01-30-2007, 10:57 AM

If you do decide to go the hollow route I would split them and rap it around a pipe the same size as your exhaust. In that manner you wouldnt experience a pressure drop due the expanded volume of the hollowed cat. Just my 2 cents though

**Chad97z** · 01-31-2007, 05:11 PM

just buy some high flow cats. that would be legal and high quality and keep your exhaust smelling cleaner. And wouldnt have to get a custom tune or special sims. So you can balance out the cost and have a system that runs more like its suppose to run. Did I mention the environment? haha Some people think removing the cats makes your car run rich. Well it doesn't. The engine burns the same way before and after removal, its just that the cats get so hot, they are designed to burn off any "left over" fuel and other chemicals that are bad for the air. So when the cat is removed it seems like its richer. The air pump pumps in extra air into the exhaust which raises the temperature of the exhaust quickly to heat the cats during startup so they can start burning off chemicals faster during start up.

**Zapper2003** · 02-01-2007, 10:35 AM

I got to looking at the car while i was servicing it yesterday, Is it me or is the cat on the dside of the motor mounted right to the manifold, and the pass. side further back, under the pass. side seat? Kinda goofy placement IMO.

**9t8z28** · 02-01-2007, 10:37 AM

Yep. 3 bolts hold the D-side cat on.

**stunna-shades** · 02-20-2007, 03:34 PM

hi flow cats cost too much...so im gonna pollute the earth...god forgive me...

**9t8z28** · 02-20-2007, 03:43 PM

Dude, these are high flow cats I had on my 97"SS". I also installed them on many, many, other cars and never had a problem with them and they flow great. They are made buy Pypes Exhaust
http://216.178.81.107/iwwida.pvx?;it...0%201?comp=ppe

**Badbird** · 02-20-2007, 05:13 PM

my cat is hollowed out, i have shorties and borla. its loud and it smells funny but i like it. less restriction means more flow. if your gonna open up your exhaust why restrict it with a cat. if you dont have emissions then gut it out. you will gain more power compared to having cats.