Punching out the "pre-cats"?
Thread Starter
Instructor
Joined: Mar 2001
Posts: 199
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From: Canyon Lake California
Punching out the "pre-cats"?
I have collected a lot of valuable information from this forum. I had previously asked about replacing the front "Y" pipe in my stock 88 including the 2 pre-cats and the main cat. Since then I sent an email to Random Technology. They informed me that they only offer the main cat. But, they referred me to TPIS.COM to get the "Y" pipe. In talking to one of the technical guys at TPIS, I learned a few things. He said most people just punch out the pre-cats and install a new main cat. He said the main cats are more efficient now and the need for pre-cats no longer exists. The car will still pass the visual inspection, and tail pipe emissions will be within limits. An added bonus is the lack of back pressure normally created by the pre-cats.
Unless someone can tell me why I shouldn't go this route, I plan to drop the "Y" pipe, punch out the pre-cats and install a new main cat.
Anyone have any thoughts, comments or suggestions on this plan?
Thanks in advance for your feedback.
Greg Sullivan (Canyon Lake, CA.)
Unless someone can tell me why I shouldn't go this route, I plan to drop the "Y" pipe, punch out the pre-cats and install a new main cat.
Anyone have any thoughts, comments or suggestions on this plan?
Thanks in advance for your feedback.
Greg Sullivan (Canyon Lake, CA.)
Burning Brakes
Joined: Nov 2000
Posts: 810
Likes: 4
From: Austria
Re: Punching out the "pre-cats"? (Greg's '88)
do it!!!!
i did it last week, it feels like a new car...revs much easier, sounds better..and..some clicking noises are gone too...best mod, i´ve ever done :D
i did it last week, it feels like a new car...revs much easier, sounds better..and..some clicking noises are gone too...best mod, i´ve ever done :D
Pro
Joined: Nov 1999
Posts: 659
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From: Woodland Ca
Re: Punching out the "pre-cats"? (Greg's '88)
Greg, how do you "punch out" the pre-cats?
Who are you going to buy your main cat from?
What's a good price to pay for a main cat?
Is a main cat something that you can instail, or do you need to paysomeone to weild it?
Sounds interesting. Thanks!
Who are you going to buy your main cat from?
What's a good price to pay for a main cat?
Is a main cat something that you can instail, or do you need to paysomeone to weild it?
Sounds interesting. Thanks!
Team Owner
Joined: Sep 2001
Posts: 62,153
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Re: Punching out the "pre-cats"? (BIG K)
well the guy at TPIS is right, the precats arent necessary anymore. These new cats flow more and still do the same job the old ones did. Im going with the full length TPIS headers and a new Random Tech or Car-sound cat when i do my exhaust.
Thread Starter
Instructor
Joined: Mar 2001
Posts: 199
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From: Canyon Lake California
Re: Punching out the "pre-cats"? (BIG K)
I saw my son do it on his Z-28. It wasn't pretty. He took a very long screwdriver and shoved it down the exhaust pipe (after removing it from the car) and just started jamming it into the guts of the converter. He used a hammer to help things along. You have to make sure you don't punch a hole in the converter housing. As more chunks of material were broken up, he just shook the pipe and the pieces fell out. He just kept doing it until it was completely empty. The guy at TPIS suggested keeping everything wet to avoid inhaling the dust that comes out of the converter.
The quote I got for the main cat was $213 from TPIS. One end of the cat is clamped on and the other is bolted on (through a flange arrangement). At least that's what the tech said. I haven't verified that. The problem will be removing the original cat. It's been in there for 14 years. I'm sure it will take some pounding and cussing to get it out. :D
Greg Sullivan
[Modified by Greg's '88, 6:25 PM 3/7/2002]
The quote I got for the main cat was $213 from TPIS. One end of the cat is clamped on and the other is bolted on (through a flange arrangement). At least that's what the tech said. I haven't verified that. The problem will be removing the original cat. It's been in there for 14 years. I'm sure it will take some pounding and cussing to get it out. :D
Greg Sullivan
[Modified by Greg's '88, 6:25 PM 3/7/2002]
Burning Brakes
Joined: Apr 2001
Posts: 992
Likes: 0
From: Atlanta GA
Re: Punching out the "pre-cats"? (Greg's '88)
I want to do this to mine as well, but have not had the time til now to do it. I might takle it today( the main cat that is)..... Please let me know what you deside on...
Thanks
Pete
Thanks
Pete
Pro
Joined: Jun 2001
Posts: 656
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From: Fort Worth TX
Re: Punching out the "pre-cats"? (Greg's '88)
Greg
I bought the 2.5" offroad Y pipe and then added the Random Tech cat and then a Borla catback system. It sure seems to work very well. And yes i have to pass emissions and have had no problem so far...
I bought the 2.5" offroad Y pipe and then added the Random Tech cat and then a Borla catback system. It sure seems to work very well. And yes i have to pass emissions and have had no problem so far...
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Instructor
Joined: May 2001
Posts: 225
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From: NY
Re: Punching out the "pre-cats"? (Greg's '88)
I felt a huge seat of the pants improvement from 2000 to 3500 RPM with a 2 1/2" front Y-pipe into a stock cat. I like the idea of hollow pre-cats to fool the CA smog ****'s!
Thread Starter
Instructor
Joined: Mar 2001
Posts: 199
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From: Canyon Lake California
Re: Punching out the "pre-cats"? (cajun86)
I'd be tempted to go the same route but I think a smog inspector here in California might notice the absence of the pre-cats. But if I just hollow them out, I won't have to worry about it.
Greg Sullivan
Greg Sullivan
Pro
Joined: Nov 1999
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From: Woodland Ca
Re: Punching out the "pre-cats"? (Greg's '88)
Does anyone know the difference between MAD's main cat, or for that matter your local muffler shop's cats?
I don't want to be cheep, but just like taxes I don't want to pay anymore than I have to.
I don't want to be cheep, but just like taxes I don't want to pay anymore than I have to.
Thread Starter
Instructor
Joined: Mar 2001
Posts: 199
Likes: 0
From: Canyon Lake California
Re: Punching out the "pre-cats"? (ConeKLR)
Excellent point. I didn't realize there were different kinds of cats (2 way versus 3 way). Before I order the one from TPIS, I will make sure it is the 3-way type. I suppose the original one is a 2-way that is assisted by the pre-cats. Maybe that's why the new main cat is now able to pass smog testing because it is a 3 way and doesn't need help from the pre-cats anymore.
Thanks for the reminder.
Thanks for the reminder.
Melting Slicks
Joined: Aug 2001
Posts: 2,753
Likes: 1
From: Fishkill NY
Re: Punching out the "pre-cats"? (Greg's '88)
Ecklers has a good deal on a DynoMax system, "Y" pipe and new main free flowing cat (This also eliminates the pre-cats and is 49 state legal). Its $250 and I put this in two weeks ago and its GREAT.. The sound improvement was very good, It has a deeper crisper tone that sounds great. Check out this post.. http://forums.corvetteforum.com/zerothread?id=244976
Instructor
Joined: Aug 2001
Posts: 138
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From: upatate ny
Re: Punching out the "pre-cats"? (Greg's '88)
How do you all get to the precats to punch them out? Do you have to cut them on an 87? Is there any way to tell if they are already gutted without removing them. My car seems to have a aftermarket wealded in so maybe someone else did the deed already ? Sorry to butt in but seemed like a good spot to ask?! :cheers: :chevy
