Hollowing out an LT5 cat on stock manifold. Anyone do it? - CorvetteForum - Chevrolet Corvette Forum Discussion

Go Back  CorvetteForum - Chevrolet Corvette Forum Discussion > C4 Corvettes, 1984 - 1996 > C4 ZR-1 Discussion
Reload this Page >

Hollowing out an LT5 cat on stock manifold. Anyone do it?

Notices
C4 ZR-1 Discussion General ZR-1 Corvette Discussion, LT5 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track

Hollowing out an LT5 cat on stock manifold. Anyone do it?

Reply

 
 
 
Old 08-09-2018, 09:27 PM
  #1  
billschroeder5842
ZenVette Master level VII
Support Corvetteforum!
Thread Starter
 
billschroeder5842's Avatar
 
Member Since: Mar 2016
Location: Southlake, TX
Posts: 3,144
Thanked 388 Times in 352 Posts
Default Hollowing out an LT5 cat on stock manifold. Anyone do it?

Has anyone ever "hollowed out" the cats on their stock LT5 exhaust manifold?

I'm doing my usual angst about exhaust upgrades on my 91 ZR1. I wondering how hollowing out the cats make a difference and if anyone had any experience with it.

I'm just curious....

billschroeder5842 is online now  
Reply With Quote
Old 08-09-2018, 10:41 PM
  #2  
JerriVette
CF Senior Member
 
JerriVette's Avatar
 
Member Since: Nov 2003
Location: Bergen county NJ
Posts: 10,000
Thanked 607 Times in 465 Posts
Default

Fwiw todays caralytic convertors are so efficent it doesnt pay to hollow them out...

there is really no benefit to doing so

hth
JerriVette is offline  
Reply With Quote
Old 08-10-2018, 01:57 AM
  #3  
FASTAZU
CF Senior Member
 
FASTAZU's Avatar
 
Member Since: Feb 2002
Location: 91 & 93 ZR-1 King of the Hill
Posts: 10,058
Thanked 269 Times in 246 Posts
2015 C4 of the Year Finalist
St. Jude Donor '16
Default

Just bit the bullet and do headers/exhaust. 91 exhaust system is not the best flowing to start with.
FASTAZU is online now  
Reply With Quote
Old 08-10-2018, 05:51 AM
  #4  
Rkreigh
CF Senior Member
 
Member Since: Dec 1999
Location: Alexandria, Virginia, USA VA
Posts: 7,610
Thanked 50 Times in 46 Posts
Default

Originally Posted by FASTAZU View Post
Just bit the bullet and do headers/exhaust. 91 exhaust system is not the best flowing to start with.
I agree

the factory headers on the early cars are tough to modify and the big can cats are tough as nails and it's better to install the headers as suggested. cats really only cost around 5 hp and due to the turbulence of a big empty can they would likely not gain much due to very poor scavenging of the engine. no bueno, sell them and use the money to do the right thing.

the stainless works headers can be had cheaper now and the obx are around 500 and seem to be OK (like to hear more).

the exhaust needs all the help it can get to let the beast breathe

Last edited by Rkreigh; 08-10-2018 at 05:53 AM.
Rkreigh is offline  
Reply With Quote
Old 08-10-2018, 07:34 AM
  #5  
zrc3john
CF Senior Member
 
Member Since: Jul 2015
Posts: 775
Thanked 43 Times in 41 Posts
Default

Originally Posted by Rkreigh View Post
I agree

the factory headers on the early cars are tough to modify and the big can cats are tough as nails and it's better to install the headers as suggested. cats really only cost around 5 hp and due to the turbulence of a big empty can they would likely not gain much due to very poor scavenging of the engine. no bueno, sell them and use the money to do the right thing.

the stainless works headers can be had cheaper now and the obx are around 500 and seem to be OK (like to hear more).

the exhaust needs all the help it can get to let the beast breathe
Yes, ZR-1 exhaust is very restrictive...Well, what do you want for a 27,000 dollar engine option....😜
zrc3john is online now  
Reply With Quote
Old 08-10-2018, 08:26 AM
  #6  
81c3
CF Senior Member
 
81c3's Avatar
 
Member Since: Dec 2005
Location: Royal Gorge area Colorado
Posts: 6,960
Thanked 215 Times in 185 Posts
Default

Originally Posted by Rkreigh View Post
I agree

the factory headers on the early cars are tough to modify and the big can cats are tough as nails and it's better to install the headers as suggested. cats really only cost around 5 hp and due to the turbulence of a big empty can they would likely not gain much due to very poor scavenging of the engine. no bueno, sell them and use the money to do the right thing.

the stainless works headers can be had cheaper now and the obx are around 500 and seem to be OK (like to hear more).

the exhaust needs all the help it can get to let the beast breathe
I would also like to know more on the OBX brand... I remember when I had my Z06, people were saying they didnt have the best experience with fit for the LS engines.... I wonder if the fit and quality is improved now....
81c3 is online now  
Reply With Quote
Old 08-10-2018, 10:24 AM
  #7  
FASTAZU
CF Senior Member
 
FASTAZU's Avatar
 
Member Since: Feb 2002
Location: 91 & 93 ZR-1 King of the Hill
Posts: 10,058
Thanked 269 Times in 246 Posts
2015 C4 of the Year Finalist
St. Jude Donor '16
Default

I have SW long tube coated headers, yes they cost more but fit was perfect only modification was the oil dipstick mount that has to be done with any header and after almost 10 years the still look new no discoloration at all. I originally had the tied to a Flowmaster exhaust now have Corsa no drone with ether setup.
FASTAZU is online now  
Reply With Quote
The Following User Says Thank You to FASTAZU For This Useful Post:
81c3 (08-10-2018)
Old 08-10-2018, 02:59 PM
  #8  
81c3
CF Senior Member
 
81c3's Avatar
 
Member Since: Dec 2005
Location: Royal Gorge area Colorado
Posts: 6,960
Thanked 215 Times in 185 Posts
Default

Yes, I had SW o my 92 several years back.... I didnt have mine coated, but yea, the fit was great and I did the install on my Kwiklift no problem. Just trying to save a buck and was hoping the OBX brand was a decent alternative.
81c3 is online now  
Reply With Quote
Old 08-10-2018, 07:59 PM
  #9  
1993C4LT1
CF Senior Member
 
1993C4LT1's Avatar
 
Member Since: Oct 2011
Location: Dallas Texas
Posts: 13,820
Thanked 318 Times in 278 Posts
Default

Originally Posted by 81c3 View Post
I would also like to know more on the OBX brand... I remember when I had my Z06, people were saying they didnt have the best experience with fit for the LS engines.... I wonder if the fit and quality is improved now....
Some people get lucky with OBX by not having to do much to make them fit right. It's a crap shoot. But if determined, you can make them fit. I would just go SW.
1993C4LT1 is offline  
Reply With Quote
Old 08-11-2018, 09:51 AM
  #10  
RossGN
CF Senior Member
 
RossGN's Avatar
 
Member Since: Jul 2002
Location: wichita falls tx
Posts: 284
Thanks: 0
Thanked 2 Times in 2 Posts
Default

Bill

May be going back to stock on my '94. If so, will be selling SS headers and B&B 3" exhaust. B&B shows its for 92-95, so not sure of fit.
RossGN is offline  
Reply With Quote
Old 08-11-2018, 11:01 AM
  #11  
ccmano
CF Senior Member
 
ccmano's Avatar
 
Member Since: Aug 2005
Location: Sparks NV
Posts: 1,265
Thanked 28 Times in 27 Posts
Default

I have OBX headers, Flowmaster cats and an OBX exhaust. Fit and finish on the headers was shockingly good, if not down right excellent. I know several people with OBX headers, all fit perfectly with the exception of having to dimple the #1 exhaust pipe to clear the steering shaft. I understand that is not unique to the OBX brand. There is no drone from the exhaust and the tone is deep and mellow unlike a Corsa. Here’s what you get at a very reasonable price.
H


ccmano is offline  
Reply With Quote
Old 08-11-2018, 03:45 PM
  #12  
zrc3john
CF Senior Member
 
Member Since: Jul 2015
Posts: 775
Thanked 43 Times in 41 Posts
Default

Originally Posted by ccmano View Post
I have OBX headers, Flowmaster cats and an OBX exhaust. Fit and finish on the headers was shockingly good, if not down right excellent. I know several people with OBX headers, all fit perfectly with the exception of having to dimple the #1 exhaust pipe to clear the steering shaft. I understand that is not unique to the OBX brand. There is no drone from the exhaust and the tone is deep and mellow unlike a Corsa. Here’s what you get at a very reasonable price.
H


I have OBX as well on my 91....Fit wasn't the best...I could tell when I got the labor bill from my mechanic.....I'm like, really man? He does the right thing for my every day car so it is what it is..For 500 bucks you can't go wrong...

I think SW headers are around triple the price..
zrc3john is online now  
Reply With Quote
Old 08-11-2018, 04:28 PM
  #13  
billschroeder5842
ZenVette Master level VII
Support Corvetteforum!
Thread Starter
 
billschroeder5842's Avatar
 
Member Since: Mar 2016
Location: Southlake, TX
Posts: 3,144
Thanked 388 Times in 352 Posts
Default

Is there a SW or OBX version that has fittings for the AIR system or is it best to just remove everything?
billschroeder5842 is online now  
Reply With Quote
Old 08-11-2018, 04:43 PM
  #14  
ccmano
CF Senior Member
 
ccmano's Avatar
 
Member Since: Aug 2005
Location: Sparks NV
Posts: 1,265
Thanked 28 Times in 27 Posts
Default

Originally Posted by billschroeder5842 View Post
Is there a SW or OBX version that has fittings for the AIR system or is it best to just remove everything?
I just removed it all. Unless you need it to pass emissions don’t bother. The only thing special I did was to have the exhaust fully welded to eliminate leaks and muffler movement. I’m extremely happy with the set up. Especially for the price difference to a SW with a Corsa. Here a pic of them installed on the new engine.
If I had to do it over again I would have had them coated or wrapped.
H



Last edited by ccmano; 08-11-2018 at 04:45 PM.
ccmano is offline  
Reply With Quote
Old 08-11-2018, 08:13 PM
  #15  
81c3
CF Senior Member
 
81c3's Avatar
 
Member Since: Dec 2005
Location: Royal Gorge area Colorado
Posts: 6,960
Thanked 215 Times in 185 Posts
Default

Originally Posted by ccmano View Post
I have OBX headers, Flowmaster cats and an OBX exhaust. Fit and finish on the headers was shockingly good, if not down right excellent. I know several people with OBX headers, all fit perfectly with the exception of having to dimple the #1 exhaust pipe to clear the steering shaft. I understand that is not unique to the OBX brand. There is no drone from the exhaust and the tone is deep and mellow unlike a Corsa. Here’s what you get at a very reasonable price.
H


Hey Hans...
Those look to be coated or chromed? They look pretty good aesthetically anyway. Did you need wire extensions for the O2 sensors? I think I had to get some with my SW headers IIRC.... Would band type clamps work? I sold my welder a few years ago... so I cant really weld them up. I have an X Pipe in place of the resonator and aftermarket mufflers that I cannot figure out what brand.... no numbers, no name on them.... nice though, polished stainless and they sound great really....Id kind of like to keep the air injection system
81c3 is online now  
Reply With Quote
Old 08-11-2018, 09:22 PM
  #16  
FASTAZU
CF Senior Member
 
FASTAZU's Avatar
 
Member Since: Feb 2002
Location: 91 & 93 ZR-1 King of the Hill
Posts: 10,058
Thanked 269 Times in 246 Posts
2015 C4 of the Year Finalist
St. Jude Donor '16
Default

Yes you need to extend the 02 wires, SW sells the with and without AIR hook-up.
FASTAZU is online now  
Reply With Quote
 
 
 


Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: