Headers HP
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Trust me; go with 1 3/4" dia. and not the 1 7/8" if you want to be in front at the end of the 1/4 mile or the end of the block! 
If I had to guess and from my experience I would say 20+ hp and/or 2 MPH+ increase in the 1/4 mile. I may have gotten more (custom fabrication/installation
) so I'm also going from what I have read. Oh, and I'm using the cheap stock (430 hp) mufflers and the car is silent at cruise with no cats.
Last edited by C7/Z06 Man; Mar 25, 2012 at 01:51 PM.
Former Vendor
Joined: Feb 2007
Posts: 2,572
Likes: 1
From: Austin Texas
The Kooks Headers gain ~25 rwhp untuned and after tuning, usually another 10 rwhp. Go with the 1 7/8" and the LS3 does great with these. Just installed a set yesterday and gained +44 rwhp and +38 ft-lbs on a 2008 Corvette with a Vararam. With the 1 7/8" Headers, at 2000 rpm gains are 20 ft-lbs.
Last edited by Brian@RPT; Mar 25, 2012 at 01:01 PM.
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Real World Results!
The Kooks Headers gain ~25 rwhp untuned and after tuning, usually another 10 rwhp. Go with the 1 7/8" and the LS3 does great with these. Just installed a set yesterday and gained +44 rwhp and +38 ft-lbs on a 2008 Corvette with a Vararam. With the 1 7/8" Headers, at 2000 rpm gains are 20 ft-lbs.
Oh, and the second place guy (410 rwhp with a A6 & NPP) is 4 tenths and over 3 MPH slower using the same but good stuff i.e. professional tune, aftermarket Vararam CAl, and 1 7/8" headers I think. Just Check it out. I rest my case!
Last edited by C7/Z06 Man; Mar 25, 2012 at 01:42 PM.
Pro
Joined: Jul 2011
Posts: 515
Likes: 1
From: Boca ARton FL
You guys are arguing over an 1/8 of an inch, I own a company that sells tubing (Kook's even buys from us sometimes)we see all kinds of variance in what is marked and what it actually measures. What I have learned about these cars in the past week is anything is better than stock!
Yes, the 1 3/4 may pull better down low on a stocker but what about if there are mods to be made in the future? My GS just dynoed 437 rwhp after the cam install with a totally stock exhaust. I was shocked. I bet I see close to a 60 hp rw gain when I install the 1-7/8 headers and 3" exhaust from a zo6 (yeah I see that it necks down a bit, I just want some stock quiet).
If all you are going to do is some light bolt ons consider 1-3/4 any major mods buy em once and get 1-7/8.
Yes, the 1 3/4 may pull better down low on a stocker but what about if there are mods to be made in the future? My GS just dynoed 437 rwhp after the cam install with a totally stock exhaust. I was shocked. I bet I see close to a 60 hp rw gain when I install the 1-7/8 headers and 3" exhaust from a zo6 (yeah I see that it necks down a bit, I just want some stock quiet).
If all you are going to do is some light bolt ons consider 1-3/4 any major mods buy em once and get 1-7/8.
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Glad you bought up that the tube diameter is not always what it is suppose to be because mine are actually "smaller" (1.60" I.D. if I remember correctly) than 1 3/4"= 1.75" I.D. 
1 5/8"= 1.625"
PS: My tubes are shorter than most and the lengths vary also but still larger in diameter than the LS3 heads exhaust ports i.e. the tubes cover the exhaust ports with no interference/restrictions.
1 5/8"= 1.625"
PS: My tubes are shorter than most and the lengths vary also but still larger in diameter than the LS3 heads exhaust ports i.e. the tubes cover the exhaust ports with no interference/restrictions.
Last edited by C7/Z06 Man; Mar 25, 2012 at 03:00 PM.
Pro
Joined: Jul 2011
Posts: 515
Likes: 1
From: Boca ARton FL
That would be correct as tubing is measured by it's outside diameter. In reality you could have a set of 1-7/8" headers made with 16 ga (.065") tubing vs a set of 1.75" headers made with 18 ga tubing (.050") and basically have the same thing.
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Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
1.60 I.D. + .059/.059= 1.718" O.D. 1 3/4" tubing= 1.750" O.D.
I would need another .032 added to the 1.60 I.D. to bring the O.D. to 1.750"
16 ga. (.065") tubing would add up to 1.730" still short of 1.750" O.D.
Last edited by C7/Z06 Man; Mar 25, 2012 at 04:05 PM.
Melting Slicks
Joined: Dec 2006
Posts: 2,186
Likes: 2
From: Woodinville WA
My "Real World" results using a "stock" OEM paper filter and housing converted to a home made CAI setup, 1 3/4" headers and an "out of the box" 93 Predator tune I think would kick A$$ on the above result if it was on a GS coupe with an A6 like mine; Check the 1/4 mile GS bolt-on listing, I"m the big dog at the moment= 11.52 @ 121.89 MPH running on the stock runcraps to booth!
Oh, and the second place guy (410 rwhp with a A6 & NPP) is 4 tenths and over 3 MPH slower using the same but good stuff i.e. professional tune, aftermarket Vararam CAl, and 1 7/8" headers I think. Just Check it out. I rest my case!
Oh, and the second place guy (410 rwhp with a A6 & NPP) is 4 tenths and over 3 MPH slower using the same but good stuff i.e. professional tune, aftermarket Vararam CAl, and 1 7/8" headers I think. Just Check it out. I rest my case!
Advanced
Joined: Mar 2007
Posts: 52
Likes: 0
From: Traverse City mi
Hey, got Billy boat fusion in back, hurricane induction, 170 degree thermo, nology wires, spoke with Billy boat and he said to run long tube headers no highflow cats in Mi. and their crossover, "may have to reflash computer", [predator], their headers and X pipe to provide 45+hp, dash may say codes (reflash), not sure from BB.
Any ideas out there??????
Any ideas out there??????
Racer
Joined: Aug 2008
Posts: 335
Likes: 27
From: Yukon Oklahoma
Read this it tells you all you need to know about headers. I just ordered LG 1 3/4 Street Series with Cats for my 2011 GS A6
http://forums.corvetteforum.com/c6-c...d-to-know.html
http://forums.corvetteforum.com/c6-c...d-to-know.html