2" Primary Headers...
At stock to lightly modified, a set of 1 3/4 tends to be all you need. If you know you are gonna be pushing over time for around 450, then 1 7/8 would be good.
The only reason I'm wondering is because many said there would be no gain between 1 3/4 and 1 7/8 on stock cubes and that you would lose low-end torque, but we have found these claims to be unsubstantiated.
There's also the issue of spark plugs and installation. Oh, so many questions! But if I'm spending $1500 on headers and a Y, I'm intent on getting all of the answers
http://www.camaro5.com/forums/showthread.php?t=63640
Keep in mind that is on an oem LS3 engine, but the results kind of suprised me.
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A few Reasons, the additional cost does not justify the gains.
They are a Tighter fit.
They are Heavier
Most manufacturers offer a 1 7/8 headers so they are easier to get.
The biggest gains from headers are in the middle of the curve where you drive most and you can't tell the difference between 1 7/8 and 2 inch, on the dyno graph or in the car.
Unless your Racing you won't miss the 5 HP at 6300 RPM, your not there enough to use it on the street.
I have Kooks 1-7/8 headers and I love them. Great fitment and good floor clearance.

I also have some for sale if interested.
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5 HP is 5 HP....People spend stupid money to gain 5 HP. Take for example an underdrive pulley or swap out an h-pipe for an x-pipe or even a new style air lid...list goes on.
If you can get 2" headers for nearly the same cost or within couple hundred dollars? why not? Significant difference in price....probably not.
The difference between either 1 3/4" or 1 7/8" and 2" is one Ulysses S. Grant. $10/hp is a pretty good price.

The only things I would be worried about at this point would be the fit. I'll be putting on solid motor mounts at the same time, so hopefully there won't be any clearance issues.
I was considering another manufacturer, but after reading about their horrible customer service I've decided to go with the more expensive stainless manufacturer. Any word on Kook's CS department?
As for weight on the 2" could not believe they were that light, I felt like I was gonna break the damn things, compared to a set of american racing 1 7/8s I just installed they were at least half the weight and fit 20x better.







