New headers require new cats?
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 897
Likes: 0
From: My Own Private Idaho
New headers require new cats?
This was an old quote from an old thread..
"If you purchase long tube headers, you will also need to replace your stock mid-pipes and catalytic converters."
I dont understand why I have to replace the cats, unless the longtubes are so long they would go past the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
This is on an LT4.
"If you purchase long tube headers, you will also need to replace your stock mid-pipes and catalytic converters."
I dont understand why I have to replace the cats, unless the longtubes are so long they would go past the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
This is on an LT4.
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
Originally Posted by CNTDRV55
I dont understand why I have to replace the cats, unless the longtubes are so long they would go past the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
Le Mans Master
Joined: Aug 2002
Posts: 6,080
Likes: 3
From: Clearwater FL
St. Jude Donor '06
Originally Posted by STL94LT1
No, you can't reuse your stock cats with long tube headers. Take a look at the stock cat placement, they are close to the short exhaust manifolds. You will also have to have your stock/aftermarket cat-back altered to run long tubes. My cat-back had to have the front tubes shortened and narrowed to run the new headers and bullet cats.
No way the factory cats will bolt up, and they are too large to be placed further back. Bullet cats are needed, or none at all.
Instructor
Joined: Oct 2005
Posts: 184
Likes: 0
From: Woodmere New York
wow...never knew this...does this also hold for a 1990 L98?...I have a borla cat back and added a random tech hi-flow cat a lil' less then a year ago...thought all I need now are headers and a front y.....??
had to edit....are you guys referring to the 2 pre-cats??...not the main cat, right??
had to edit....are you guys referring to the 2 pre-cats??...not the main cat, right??
Last edited by cakes751; Oct 14, 2006 at 09:57 PM.
Melting Slicks
Joined: Jun 2004
Posts: 3,032
Likes: 4
Originally Posted by cakes751
wow...never knew this...does this also hold for a 1990 L98?...I have a borla cat back and added a random tech hi-flow cat a lil' less then a year ago...thought all I need now are headers and a front y.....??
had to edit....are you guys referring to the 2 pre-cats??...not the main cat, right??
had to edit....are you guys referring to the 2 pre-cats??...not the main cat, right??
The L98 placement is different, you're cat can be retained, though you'll lose your precats.
Instructor
Joined: Oct 2005
Posts: 184
Likes: 0
From: Woodmere New York
Originally Posted by mikey whipreck
They are referring to the 2 cat locations on LTx engines.
The L98 placement is different, you're cat can be retained, though you'll lose your precats.
The L98 placement is different, you're cat can be retained, though you'll lose your precats.
Le Mans Master
Joined: Oct 2004
Posts: 7,706
Likes: 485
From: Everett WA
C4 of Year Finalist (appearance mods) 2019
Originally Posted by CNTDRV55
This was an old quote from an old thread..
"If you purchase long tube headers, you will also need to replace your stock mid-pipes and catalytic converters."
I dont understand why I have to replace the cats, unless the longtubes are so long they would go past the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
This is on an LT4.
"If you purchase long tube headers, you will also need to replace your stock mid-pipes and catalytic converters."
I dont understand why I have to replace the cats, unless the longtubes are so long they would go past the orig cats.
I see that for EM headers that you need extensions. If that is true then shouldn't I be able to attach the extensions to the orig cats.
This is on an LT4.
after you do it and like was said above, you'll need to replace the stock cats. Perhaps with RT stainless high flow bullet cats
Burning Brakes
Joined: Jul 2005
Posts: 758
Likes: 6
From: Gainesville, FL
You may want to look at my old write-up if you are about to do this installation - http://forums.corvetteforum.com/show...+works+install - It is for SWs LTs, but it should still answer some other questions for you. Good luck 
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Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 897
Likes: 0
From: My Own Private Idaho
Thanks for the enlightenment!
I guess I'll be getting new cats as I need to pass emissions.
On that subject....since I'll be running with cats and therefore dont need the o2 sims, is there any other obstacle to passing emissions with a header?
On that subject....since I'll be running with cats and therefore dont need the o2 sims, is there any other obstacle to passing emissions with a header?
Race Director
Joined: Jan 2002
Posts: 12,263
Likes: 86
From: O'Fallon Missouri
Originally Posted by CNTDRV55
is there any other obstacle to passing emissions with a header?