High Flow Cats with Shorty Headers? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

Aaron1121 · 12-16-2009, 04:04 PM

I am installing a catback system. I would love to also install some long tube headers, but since I live in the golden state I won't pass a smog inspection with them. I don't really feel like swapping out the headers before every smog inspection.

From everything I've seen on the forums, it looks like most people are seeing 25-30 HP gains with longtubes and high flow cats, and people with shorties and stock cats are getting 4-9HP. It seems like the most restrictive part is the stock cats.

Has anyone tried just replacing the stock cats, or shorty headers with high flow cats? What type of gains have you seen?

If shorties and high flow cats worked well, it would be pretty easy to just swap the cats with a couple bolts prior to the inspection.

Thoughts?

BIGK909 · 07-02-2010, 03:46 AM

nobody?

The Yeti · 07-02-2010, 03:55 AM

Different cars but a buddy of mine with a G8 has shorty headers with stock cats and a corsa catback and made 20 less rwhp than myself with solo high flow cats, stock manifolds and solo catback. We have got our tunes from the same dyno also. Personally I think you may gain a little power in the mid range but not enough to warrant the cost of shorties unless you want more sound to go with your high flow cats. Well if you plan on going the maggie route you may have to get shorties anyway to get as much flow as possible.

nfamous209 · 07-02-2010, 05:54 AM

first u dont have to smog ur car for atleast 5 years since its new. 2nd tons of smog shops out there look to see if u have cats, thats it. not if theyre relocated not if u have LT's. if you have cats then ur good. u just need to find one. and u can install LT's and Catted mid pipes.

topgun1 · 07-02-2010, 06:53 AM

check my thread out aaron, you may find it helpful. I have DT shorty headers and SOLO hiflow cats.

http://www.camaro5.com/forums/showthread.php?t=91945

axis · 07-02-2010, 10:15 AM

Regardless of what "some shops" may do/say, the letter of the law states that if you move or replace FUNCTIONAL cats, you are in violation of the inspection. Take it for what's worth and make your own decision from there.

bi11ymc · 07-02-2010, 10:25 AM

Quote:

Originally Posted by axis

Regardless of what "some shops" may do/say, the letter of the law states that if you move or replace FUNCTIONAL cats, you are in violation of the inspection. Take it for what's worth and make your own decision from there.

I am hoping the Magnaflow replacement cats I am getting will fool the visual inspection, since they look identical and flow a bit better, or so they say. I won't know until I get them installed (parts are ordered, install not scheduled, yet) and go through inspection (September).

Wilburbeest · 07-03-2010, 07:54 AM

Gen III/IV engines essentially have shorty headers from the factory. In other words it's a gigantic waste to buy an aftermarket set. I am just starting to really learn about the 5th gen so I don't know what all is available at this point, but if there is a 50 state legal (C.A.R.B. approved) mid length header available that may be something you want to check into. Those will not move the cats back like LTs do and would be 100% legal. Also, as true as it is that swapping working cats is illegal, good luck to any inspector that tries to prove they didn't replace dysfunctional cats or ones that were removed by another owner. If you have cats and EGR you can often pass a visual with LTs too but with that one you're really at the mercy of the inspector. If they look for the C.A.R.B. sticker on the headers you will have a problem. Granted nothing stops you from going to as many shops as you need to in order to pass. If you don't mind some possible hassle I'd get LTs with emissions hookups and some high flow cats.

bi11ymc · 07-03-2010, 08:43 AM

Not a gigantic waste since. The DT Shorties are lighter weight, look better and because of the ceramic coating, will allow less heat into the engine compartment. That is why I am going with them.

Wilburbeest · 07-03-2010, 09:23 AM

Quote:

Originally Posted by bi11ymc

Not a gigantic waste since. The DT Shorties are lighter weight, look better and because of the ceramic coating, will allow less heat into the engine compartment. That is why I am going with them.

1. Lighter weight by how much? Is this weight savings anything that will ever be discernible to you? I think not unless you are building a drag car and are doing several other things along with it that add up to a large overall weight savings.

2. If a $500 (plus hassle or cost of install) under-hood decoration is your thing that's your business. This is America.

3. Lower temps in the engine bay are a plus, but assuming the current heat is not causing any problems I don't see how this is a major factor? If it was you would see it reflected on dynos. On a stockish car the only purpose I could see it serving is maybe (big maybe) helping hoses last longer. Those should really be changed long before they have a chance to be a problem though.

I will concede that they are at least a little better than stock manifolds and may manifest a more notable gain over stock manifolds on a decently modded engine or a high RPM application than they do stock. I do see that you have a cam coming soon so maybe that will make them a bit more useful. Just speculation there. But what is not speculation is the for the cost/hassle involved I personally find shortys on LSx engines extremely underwhelming. Its not my goal to attack you dude and sorry if my opinion offends you but it is my opinion. I like mods that actually make my car do something notably different than it already does. If you're into paying $100/hp that's your business.

bi11ymc · 07-03-2010, 10:43 AM

Quote:

Originally Posted by Wilburbeest

1. Lighter weight by how much? Is this weight savings anything that will ever be discernible to you? I think not unless you are building a drag car and are doing several other things along with it that add up to a large overall weight savings.

2. If a $500 (plus hassle or cost of install) under-hood decoration is your thing that's your business. This is America.

3. Lower temps in the engine bay are a plus, but assuming the current heat is not causing any problems I don't see how this is a major factor? If it was you would see it reflected on dynos. On a stockish car the only purpose I could see it serving is maybe (big maybe) helping hoses last longer. Those should really be changed long before they have a chance to be a problem though.

I will concede that they are at least a little better than stock manifolds and may manifest a more notable gain over stock manifolds on a decently modded engine or a high RPM application than they do stock. I do see that you have a cam coming soon so maybe that will make them a bit more useful. Just speculation there. But what is not speculation is the for the cost/hassle involved I personally find shortys on LSx engines extremely underwhelming. Its not my goal to attack you dude and sorry if my opinion offends you but it is my opinion. I like mods that actually make my car do something notably different than it already does. If you're into paying $100/hp that's your business.

Why do people change anything about the car? People spend much more just to change the sound with a cat-back and it does nothing to performance. I say, it is only money and if shorty headers allow me to stay in the county I live in, improve many aspects of the car no matter how small, and cost so little, I say "why not"?

topgun1 · 07-05-2010, 06:51 AM

Quote:

Originally Posted by bi11ymc

Not a gigantic waste since. The DT Shorties are lighter weight, look better and because of the ceramic coating, will allow less heat into the engine compartment. That is why I am going with them.

yes

third1 · 07-05-2010, 09:08 PM

My shorties gave the the car a little bit more growl out of the Solo exhaust and look great for only $200 new.

Ivan @ Southwest Speed · 07-05-2010, 11:33 PM

Definitely replace the Cats with some high flow/spun units to realize better HP gains.

Agreed, the factory manifolds are not bad at all.

The Shorties Def give a better look, just don't look for LT Header performance out of them.

Best of luck to you sir!
Ivan

12-16-2009, 04:04 PM	#1
Aaron1121 Drives: 2010 CGM 2SS/RS Join Date: Jul 2008 Location: . Posts: 80	High Flow Cats with Shorty Headers? I am installing a catback system. I would love to also install some long tube headers, but since I live in the golden state I won't pass a smog inspection with them. I don't really feel like swapping out the headers before every smog inspection. From everything I've seen on the forums, it looks like most people are seeing 25-30 HP gains with longtubes and high flow cats, and people with shorties and stock cats are getting 4-9HP. It seems like the most restrictive part is the stock cats. Has anyone tried just replacing the stock cats, or shorty headers with high flow cats? What type of gains have you seen? If shorties and high flow cats worked well, it would be pretty easy to just swap the cats with a couple bolts prior to the inspection. Thoughts?

07-02-2010, 03:46 AM	#2
BIGK909 Drives: 2010 Camaro LT/RS VR Join Date: Jun 2010 Location: SoCal Posts: 84 View My Garage	nobody? __________________ -MRT V1.0, H&R Springs, Injen CAI

07-02-2010, 03:55 AM	#3
The Yeti On the wrong side of town Drives: Pontiac G8 GT Join Date: Jun 2010 Location: Bay Area Cali Posts: 59	Different cars but a buddy of mine with a G8 has shorty headers with stock cats and a corsa catback and made 20 less rwhp than myself with solo high flow cats, stock manifolds and solo catback. We have got our tunes from the same dyno also. Personally I think you may gain a little power in the mid range but not enough to warrant the cost of shorties unless you want more sound to go with your high flow cats. Well if you plan on going the maggie route you may have to get shorties anyway to get as much flow as possible. __________________ *The Yeti - just an 11sec NA grocery getter!!!* 08 G8 GT Premium/Sports Package W/Sunroof Pat G Tuned, Heads/Cam/gears/Stalled, Dropped, Brembos on all 4 corners and every bolt on under the sun. April 2011 G8 of the Month June 2012 G8 of the Month April 2013 G8 of the Month @G8BOARD.COM

07-02-2010, 06:53 AM	#5
topgun1 Drives: 10 SIM 2SS/RS LS3 Join Date: May 2008 Location: Winston-Salem, NC Posts: 1,940 View My Garage	check my thread out aaron, you may find it helpful. I have DT shorty headers and SOLO hiflow cats. http://www.camaro5.com/forums/showthread.php?t=91945 __________________ 5th Gen Camaros of the Carolinas SIM, 2SS/RS LS3 5/7/11 453.9 RWHP 427.5 RWTQ VMS Stage 2.5 Comp Cams kit, Cold Air Inductions intake, ADM race scoop, DT 1 3/4" headers, Solo cats, 3" Magnaflow catback, Pypes cutouts, HP tune, H&R SuperSport springs, Eibach sways/spacers, TexasSpeed UD pulley, LSR tensioner pulley, Barton shifter, skip shift eliminator, powder-coated calipers, R1 concept rotors, StopTech pads, Granatelli wires, Lloyds mats, tint, AAC afterburner taillamps, AAC scanner/sidemarkers, SRP pedals, custom engine cover, black bowties, Ridergraphix hood spears....

07-02-2010, 10:15 AM	#6
axis Search Ninja Drives: 2010 Black 2SS/RS A6 Join Date: Oct 2009 Location: Central Ark Posts: 7,183	Regardless of what "some shops" may do/say, the letter of the law states that if you move or replace FUNCTIONAL cats, you are in violation of the inspection. Take it for what's worth and make your own decision from there. __________________ 2010 Black 2SS/RS A6 Halltech CF 102 fed GPI modded intake manifold Bo (knows) White ported TB Kooks LT's/ Dynomax VT Pfadted (springs/sways) Dyno tuned by Rhino and GPI I once parallel parked a train.

07-02-2010, 05:54 AM	#4
nfamous209 Drives: 2002 Camaro z28 Join Date: May 2008 Location: patterson, ca Posts: 413	first u dont have to smog ur car for atleast 5 years since its new. 2nd tons of smog shops out there look to see if u have cats, thats it. not if theyre relocated not if u have LT's. if you have cats then ur good. u just need to find one. and u can install LT's and Catted mid pipes.

07-03-2010, 07:54 AM	#8
Wilburbeest Think With Your Dipstick! Drives: 1997 Camaro Z28 Join Date: Jul 2010 Location: Spokane, WA Posts: 185	Gen III/IV engines essentially have shorty headers from the factory. In other words it's a gigantic waste to buy an aftermarket set. I am just starting to really learn about the 5th gen so I don't know what all is available at this point, but if there is a 50 state legal (C.A.R.B. approved) mid length header available that may be something you want to check into. Those will not move the cats back like LTs do and would be 100% legal. Also, as true as it is that swapping working cats is illegal, good luck to any inspector that tries to prove they didn't replace dysfunctional cats or ones that were removed by another owner. If you have cats and EGR you can often pass a visual with LTs too but with that one you're really at the mercy of the inspector. If they look for the C.A.R.B. sticker on the headers you will have a problem. Granted nothing stops you from going to as many shops as you need to in order to pass. If you don't mind some possible hassle I'd get LTs with emissions hookups and some high flow cats. __________________ - Willy 1997 Camaro Z28 (LT1/T56): K&N CAI \| Kooks 1 3/4" LTs \| 3" Custom Duals \| UMI LCAs w/ relocation brackets \| UMI adj. panhard bar \| UMI adj. torque arm \| Koni SA shocks \| Strano Springs \| Ram Powergrip clutch \| Pro 5.0 shifter \| skip shift eliminator kit \| WS6 Store rotors \| Hawk HPS pads

07-03-2010, 08:43 AM	#9
bi11ymc "Silver Street" Drives: 2010 2SS/RS L99 Join Date: Oct 2009 Location: Franklin, TN Posts: 707	Not a gigantic waste since. The DT Shorties are lighter weight, look better and because of the ceramic coating, will allow less heat into the engine compartment. That is why I am going with them. __________________ Silver Street - 2010 Camaro 2SS/RS, SIM, Gray, Cyber Gray Rally Stripes, Polished Wheels, Automatic (L99) - 553 RWHP/510 RWTQ CAI Inc., ARH LT Headers with Cats, Borla Touring Cat-Back; Pfadt Coil Overs, Sway Bars, End Links, and Trailing Arms; Comp Cams Blower Cam, Dual Springs, Push-Rods, and Lifters; GM LS2 Lifter Trays, 6.2 MLS Head Gaskets, Crank Bolt, and LS2 Front Cover; 3-Bolt Conversion Timing Gear, Katech C5R Timing Chain, ARP LS2/LS3 Head Bolt Kit, Melling Hi Volume Oil Pump, TVS 2300 Supercharger (Black); Build by Vengeance Racing; Custom Tune by Vengeance Racing Last edited by bi11ymc; 07-03-2010 at 08:44 AM. Reason: waste (not waist) lol

07-05-2010, 09:08 PM	#13
third1 speed freak Drives: 2015i Cadillac Escalade,10 IOM 2ss Join Date: Jun 2009 Location: Neenah Wi Posts: 1,143 View My Garage	My shorties gave the the car a little bit more growl out of the Solo exhaust and look great for only $200 new. __________________ Current:2015i Cadilac Escalade,2016 Lexus RC350,2011 CVO StreetGlide cammed,tuned & loud. 2010 IMO/IO,custom stripes,GFX,sunrf,solo exhaust,JBA shorties,rotofab,Jannetty tune,Pfadt,JLw6 Audison&Hertz,7/4/09 2GIFKIEJ6A9123779Del 7/10/09 Former Camaros 72 LT1 Z28, 86 z28 [SIGPIC]

07-05-2010, 11:33 PM	#14
Ivan @ Southwest Speed Drives: '15 Z06, '01 NBM SS, '97 SS Join Date: May 2009 Location: Rio Rancho, NM Posts: 12,170	Definitely replace the Cats with some high flow/spun units to realize better HP gains. Agreed, the factory manifolds are not bad at all. The Shorties Def give a better look, just don't look for LT Header performance out of them. Best of luck to you sir! Ivan

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
V8 Camaro Performance Upgrades List	Milk 1027	Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons	93	08-30-2021 05:56 PM
Video: Stainless Works Headers, Cats and Exhaust	EVS Motors Inc.	Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons	34	02-26-2012 02:01 AM
Doug Thorley Headers V6 shorty headers	DOUG THORLEY HEADERS	V6 Bolt-Ons & Tunes	5	09-10-2009 04:58 PM
Dynetech Long Tube Headers With Cats / Predator Programmer Package - $1395.99	tbyrne	V8 Bolt-Ons & Tunes	0	09-06-2009 07:27 AM
American Racing Headers with Cats	LPFSTheFett	V8 Bolt-Ons & Tunes	16	08-17-2009 01:29 PM