Header Question
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,756
Likes: 267
Header Question
I'm thinking of making a few performance upgrades to my '11 GS coupe (6spd manual) with the goal of increasing low rpm torque and achieving 500+ hp. The plan includes adding the Halltech Beehive air induction, a slightly hotter cam, headers, and a tune. But I'd perfer to NOT cut the factory NPP exhaust.
So the question is this: Are there headers out there that replace the stock factory manifolds without modification to the exhaust system .... and what is the performance difference between the short tube vs. long tube designs?
So the question is this: Are there headers out there that replace the stock factory manifolds without modification to the exhaust system .... and what is the performance difference between the short tube vs. long tube designs?
Burning Brakes
Joined: Sep 2009
Posts: 959
Likes: 3
From: Hartford CT
The big gains from long tubes happen in the middle of the powerband. This is due to the longer primary runners. A short tube header is a compromise and will be an improvement but not offer the typical gains of a full long tube.
The idea behind the longer primary runner is to take advantage of the scavaging effect at a more usable RPM. Factory manifolds actually dont flow that bad, but their ultra short runners offer no scavaging ability at any usable rpm.
Bottom line, if you are going for headers you might as well go full length. However if you stay with the factory mainfolds and cats it will be difficult to reach your power goals.
The idea behind the longer primary runner is to take advantage of the scavaging effect at a more usable RPM. Factory manifolds actually dont flow that bad, but their ultra short runners offer no scavaging ability at any usable rpm.
Bottom line, if you are going for headers you might as well go full length. However if you stay with the factory mainfolds and cats it will be difficult to reach your power goals.
Racer
Joined: Mar 2012
Posts: 388
Likes: 0
From: NC
i have a '12 GS 6 speed manual. i just did kooks 1 3/4 headers with offroad x pipe, K&N CAI, and tune. I still have my NPP exhaust. First off....its sounds amazing with the valves open! i have a mild to wild switch but i leave them open 99.9% of the time 
It definitely has quite a bit more power. plenty for me. if you do a pretty big cam like the LG G6x3 cam you will make near 500whp but you will lose some driveability with that big cam. with a mild cam u can make roughly 440whp or so. or you can bolt on a supercharger and make a ton of power and retain stock driveability haha
It definitely has quite a bit more power. plenty for me. if you do a pretty big cam like the LG G6x3 cam you will make near 500whp but you will lose some driveability with that big cam. with a mild cam u can make roughly 440whp or so. or you can bolt on a supercharger and make a ton of power and retain stock driveability haha
Burning Brakes
Joined: Nov 2011
Posts: 1,042
Likes: 283
From: West Dundee IL
2024 C5 of the Year Finalist - Modified
St. Jude Donor '12-'13
Pretty much any header system for the C6 uses the stock axle back (mufflers) unless otherwise specified. You get long tube headers and an intermediate pipe that the mufflers slide into. You still retain the factory npp. Currently I have TSP long tubes with a catless intermediate connected to the factory mufflers.
Safety Car
Joined: Sep 2006
Posts: 4,075
Likes: 6
From: Wilmington NC
I have the long tube ARHeaders with 3" x-pipe & hi-flow cats that connect to the stock 2 1/2" NPP axle back exhaust that I added previously.
Former Vendor
Joined: Feb 2007
Posts: 2,572
Likes: 1
From: Austin Texas
We have had a few C6's hit 500 rwhp with a medium sized cam. They drive great and sound bad ***. With the Headers, that is a 25 rwhp gain before tuning. After tuning, expect another 10 rwhp. With the CAI added, most M6's are over 430 rwhp after tuning. The gains are throughout the entire rpm band and the LS3 loves bolt-ons.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Burning Brakes
Joined: Aug 2004
Posts: 1,207
Likes: 147
From: St. Louis MO
jost6453;
It is true that you can generally expect a 25 rwhp gain before tuning with the headers, and another 10 rwhp after tuning. But I will say that extra 40+ horse you want from the cam + another tune is not going to net you a mild-mannered beast.
What the tuners don't tell you is that you'll be married to the optimium tune for your city. They will have used up all the octane & spark advance margins GM programmed into the PCM, and beware if you drive out-of-town and get a substandard load of gas or you're on a hwy grade on a hot day because the engine will be knocking.
It is true that you can generally expect a 25 rwhp gain before tuning with the headers, and another 10 rwhp after tuning. But I will say that extra 40+ horse you want from the cam + another tune is not going to net you a mild-mannered beast.
What the tuners don't tell you is that you'll be married to the optimium tune for your city. They will have used up all the octane & spark advance margins GM programmed into the PCM, and beware if you drive out-of-town and get a substandard load of gas or you're on a hwy grade on a hot day because the engine will be knocking.
Burning Brakes
Joined: Nov 2011
Posts: 1,042
Likes: 283
From: West Dundee IL
2024 C5 of the Year Finalist - Modified
St. Jude Donor '12-'13
jost6453;
It is true that you can generally expect a 25 rwhp gain before tuning with the headers, and another 10 rwhp after tuning. But I will say that extra 40+ horse you want from the cam + another tune is not going to net you a mild-mannered beast.
What the tuners don't tell you is that you'll be married to the optimium tune for your city. They will have used up all the octane & spark advance margins GM programmed into the PCM, and beware if you drive out-of-town and get a substandard load of gas or you're on a hwy grade on a hot day because the engine will be knocking.
It is true that you can generally expect a 25 rwhp gain before tuning with the headers, and another 10 rwhp after tuning. But I will say that extra 40+ horse you want from the cam + another tune is not going to net you a mild-mannered beast.
What the tuners don't tell you is that you'll be married to the optimium tune for your city. They will have used up all the octane & spark advance margins GM programmed into the PCM, and beware if you drive out-of-town and get a substandard load of gas or you're on a hwy grade on a hot day because the engine will be knocking.
Burning Brakes
Joined: Aug 2004
Posts: 1,207
Likes: 147
From: St. Louis MO
This is completely inaccurate. No matter what parameters are changed in the tune your car still has a MAF, knock and O2 sensor. Your PCM will adjust your fuel tables. The tune merely optimizes the air/fuel for your mods. If you put headers on a car and don't tune it the sensors will compensate so you don't melt your engine. A tune adds more fuel and spark advance to optimize the increase in exhaust scavenging. If you get a bad tank of gas or drive in high altitude the PCM will make adjustment to protect the engine. You won't have optimum performance but the same will happen to a stock tuned car.
If you're going demand a high HP number from a few simple bolt-on's the tuner is going to jack around with the PE tables and commanded A/F ratio, and timing so on the dyno, it shows a power increase.
They can't hit a high artificial HP number & care about protecting for things like driving up Baker grade at 70mph in the desert heat and not allow anything to overheat, knock, or otherwise fail. GM's left maybe 5% on the table without compromising on the longevity of the life of the engine.
With a "slightly hotter cam, headers," and a realistic tune, you're going to see an increase, but not to 500HP, and if you try it, you're chipping away the longevity of your engine.
Burning Brakes
Joined: Nov 2011
Posts: 1,042
Likes: 283
From: West Dundee IL
2024 C5 of the Year Finalist - Modified
St. Jude Donor '12-'13
By putting a higher lift cam in a vehicle you're sacrificing longevity of the valve trains. Does that mean that the car won't go 100K miles? Nope. You may sacrifice some longevity but every day wear and tear is different on any vehicle. Going up a steep grade in 100 degree heat is going to take it's toll on a totally stock car. Portraying that because you have a tuned car you have to only drive it in you neighborhood is ludicrous. I have always had dyno tunes and bolt-on's done to my cars. I drive them any where in any conditions including high altitude and extreme heat. My knock sensors are enabled and I have never toasted a motor.
Burning Brakes
Joined: Aug 2004
Posts: 1,207
Likes: 147
From: St. Louis MO
By putting a higher lift cam in a vehicle you're sacrificing longevity of the valve trains. Does that mean that the car won't go 100K miles? Nope. You may sacrifice some longevity but every day wear and tear is different on any vehicle. Going up a steep grade in 100 degree heat is going to take it's toll on a totally stock car. Portraying that because you have a tuned car you have to only drive it in you neighborhood is ludicrous. I have always had dyno tunes and bolt-on's done to my cars. I drive them any where in any conditions including high altitude and extreme heat. My knock sensors are enabled and I have never toasted a motor.
Burning Brakes
Joined: Nov 2011
Posts: 1,042
Likes: 283
From: West Dundee IL
2024 C5 of the Year Finalist - Modified
St. Jude Donor '12-'13
What the tuners don't tell you is that you'll be married to the optimium tune for your city. They will have used up all the octane & spark advance margins GM programmed into the PCM, and beware if you drive out-of-town and get a substandard load of gas or you're on a hwy grade on a hot day because the engine will be knocking.
Burning Brakes
Joined: Aug 2004
Posts: 1,207
Likes: 147
From: St. Louis MO
Not quarreling at all, just trying to make the OP aware that you posted inaccurate information that should be disregarded.
A dyno tune by no means "marries" you to "your city". Parameters can be taken to limit but the PCM still does it's job as designed to protect the engine. I just can't stand when somebody posts blatantly wrong information on a forum in response to somebody who doesn't understand the topic fully. I would hate to see a person be turned off to modifying a car because of the BS you posted. 500HP can be made, it has been by several different shops. Dyno's vary, that doesn't mean that the tune is maxed out and is dangerous.
A dyno tune by no means "marries" you to "your city". Parameters can be taken to limit but the PCM still does it's job as designed to protect the engine. I just can't stand when somebody posts blatantly wrong information on a forum in response to somebody who doesn't understand the topic fully. I would hate to see a person be turned off to modifying a car because of the BS you posted. 500HP can be made, it has been by several different shops. Dyno's vary, that doesn't mean that the tune is maxed out and is dangerous.
Most stock LS3's make about 370-something rwhp on the average DynoJet on average weather days. To post 500HP reliably, with headers, cam & tune (in the real world were people are not mislead,) that's going to be more than mild cam timing and headers. I'm saying wilder cam timing, and an agressive tune.
Read: The OP is not going to have a mild-mannered car, there will be some compromises in drivability and or reliability.
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,756
Likes: 267
I appreciate the lively debate, but I'm afraid I was not very clear describing the goal. The GS is rated at 436 hp. I 'm considering mods that would take that number to ~ 500hp .... so ~ 65 hp gain. I had not intended to go for 500 rwhp performance. So with that being clarified, can I get there (or close) with a Halltech Beehive, long tube headers, & a tune?
Burning Brakes
Joined: Feb 2011
Posts: 833
Likes: 470
From: Goodyear AZ
I just had Kooks headers and X pipe w/ cats installed and retuned. I already had the Corsa Sports on and a Blackwing CAI and tune. I was at 396hp to the wheels last year when I had those mods dynoed and on my baseline run the other day I had the same hp on a different dyno, different shop. After the install of the headers and X pipe and retune I had 458hp to the wheels. I could not be happier w/ the great sound and the performance gain. The engine spins up so much faster and you can really feel the difference. I was a little surprised at how much of a gain in hp we got, the LS3 does love the boltons, I wish I had done this sooner.
Burning Brakes
Joined: Nov 2011
Posts: 1,042
Likes: 283
From: West Dundee IL
2024 C5 of the Year Finalist - Modified
St. Jude Donor '12-'13
I appreciate the lively debate, but I'm afraid I was not very clear describing the goal. The GS is rated at 436 hp. I 'm considering mods that would take that number to ~ 500hp .... so ~ 65 hp gain. I had not intended to go for 500 rwhp performance. So with that being clarified, can I get there (or close) with a Halltech Beehive, long tube headers, & a tune?
