x phantom x

iTrader: (14)

I hate asking these types of questions, but after a ton of searching I just can't find the answer I am looking for.

I have a 402ci LS2 w/ LS7 heads that I am redoing and putting into a C5 (hoping for the 500-550rwhp range). I believe I've narrowed the brand down to the Kooks, since it seems that everyone has great luck with them. However, it appears the "best" primary size is up for debate. There are the stepped 1 3/4", 1 3/4" to 1 7/8", or the 1 7/8." Which would be the best to go with? Some say bigger is better, while others seem to feel the higher velocities of the smaller primaries is the way to go.

My second question is about the X pipe. I would like to have the headers into an X-pipe with cats, then into the stock cat-back w/ dual cut-outs. Is there enough room to add the cutout to the 3" - 2 1/2" X pipe, or would I need to use the 3"-3" and get something custom fabricated to do this? Are the cats that come with the kooks any good, or should I just get the off-road x pipe and throw some random tech cats in there?

Any thoughts would be helpful.

slow trap

iTrader: (22)

those ls7 heads flow big numbers up top so i would suggest the 1 7/8 to squeeze out all that hp.i guess it boils down to "do i want to lose some bottom end but gain up top ?" i have no idea about the x pipe.

davered00ss

iTrader: (4)

I would go with the 1 7/8"

chevynation

iTrader: (8)

one thing you might consider is the ls7 exhaust port really doesn't flow all that well compared to the intake, so the 1 3/4 might compliment it better, I dunno. if you had ls1/6 style heads, i'd go with 1 7/8.

its all in the combo

x phantom x

iTrader: (14)

Yup, this is one of the only reasons I was considering the 1 3/4" or stepped version. Although everyone says 1 7/8" when a 402 is mentioned ... the LS7 exhaust ports only flow in the 230's in the lift range I will use. I'm not sure if this has any effect on what type of headers I should get, which is one of the main reasons I wanted to ask this.

I emailed LG about a month ago and they said 1 7/8" ... I emailed them again a week or so ago, and that time they recommended their 1 3/4" ... not sure why the change.

DrkPhx

iTrader: (15)

I run QTP 1-7/8" headers for my LS2 402 (AFR 225's) and I can tell you the car has an over adundance of low end torque. The 4000 stall does help.

98Z28CobraKiller

iTrader: (17)

use the 1 3/4's. Use the 3" off road y and have a muffler shop make you some true dual 3"ers and dump them before the axles.

x phantom x

iTrader: (14)

It's going in a corvette, so there is no Y and it already has true duals ... and like I said in the first post I am looking to keep the stock cat-back exhaust (for occassions I want it to be quiet), and just toss dual electronic cut-outs in there (for when I want it loudddd).

TheBlurLS1

iTrader: (8)

I say go with the 1-7/8", last thing you want to be thinking after it's said and done is woulda/coulda/shoulda.

DanZ28

iTrader: (5)

Ditto!

Don't think you will lose any torque down low with them on your 402. And if you use a power adder at all, these will be the ticket.

Dan

SSilverSSurfer

iTrader: (8)

1 7/8ths kooks or qtp

x phantom x

iTrader: (14)

.
Cool ... seems like the 1 7/8" are still the way to go. Just wanted to make sure I was doing the right thing.

Does anyone have any idea about the dual cut-outs fitting into the kooks X-Pipe? I'll probably just call one of the sponsors if not.