BaRcA4EvEr

hi guys ..

I own a 2008 ls3 c6 with borla cat back & vararam cai and I am planing to install kooks headers to be the last modification to my car

so which size of the headers should I install

1 3/4 or 1 7/8 ??

2.5 in or 3 in X-pypes ??

Motorhead-47

You'll get lots of opinions on this question. I had the same question four months ago and after reading extensively and looking at results from others I came to the conclusion that other than a small additional cost up front there is no reason not to go with the 1 7/8" headers with a 3" x-pipe for the LS3 motors.

3 Z06ZR1

1 7/8's with 3" x-pipe is the way to go for the LS-3
I had 1 3/4 with 2 1/2 which were ok till I added F/I.
Then a lot of backpressure and heat was reduced by going to 1 7/8
with 3". Plus a nice boost in power.

LS1LT1

If you're absolutely not going to be modifying the car any further than that then I would go with the 1 3/4" with 2.5".
If there is even an outside chance of you considering an aggressive heads and cam package, forced induction or even a bigger motor (416 etc.) then go with the 1 7/8".

Vito.A

I agree, if you do not plan any additional mods, the 1 3/4" is perfect.

You should also consider the American Racing Headers and X pipe. They also have 1 3/4 or 1 7/8" primary tube headers for the C6. They are oustanding quality products built here in the US (Amityville NY).

BaRcA4EvEr

thx guys ..

headers will be my last modification .. I'm not planing to install heads and cam or any forced induction ..

1 3/4 will be better for me with the 2.5 in x pypes

is it ok if took the 3 in .. any big diffrance ??

Dulimon

Regarding the header primary size to mid pipe this is my experience on my car. Originally going with 1 ¾ headers tied into 3” mids. After in shop consultation now on site…again looking at the 1 ¾ side. I went with another brand recommended by the shop to begin with resulting in 1 7/8 headers tied into 2 ½ mids to keep the velocity up to promote evac velocity and stock power curves on a bolt on LS3. Again as skeptical as I am…I left the shop humbled leaving stop lights with a spin and once I got out on the open highway new they didn’t point me wrong.
To be open they new my future upgrades ATOI (At Time Of Install) would be a cam at least so as pointed out larger header primaries was in order but a small primary with 2 1/5 mids was the way to go to keep low to mid curves increase due to velocities yet these mirrored the exact HP/TQ curves of the stock LS3 only higher pointed by the shops dyno and pointed our by the exhaust manufacture upon consultation. This was to keep maximum curves until the need for a 3” mid due to the further mods. So, regarding my exp…keep your velocities up for a stock car as pointed out unless you want top end grunt yet the 1 7/8 pirmaries tied to 2 1/5 mids seem to be a good compromise. The old discussion of losing torque down low with larger header primaries seems to have faded a year ago depening on your shops turner.

oldmansan

There hasn't been any conclusive evidence that either is better than the other. Do a search on Powerlabs' posts. He pretty much proved they (1 3/4s and 1 7/8s) are for all intents and purposes even.

San

AndrewZPSU

I have 1-7/8 kooks Z06 headers on mine. 501 rwhp =)

Dulimon

You are true sir as I mentioned...depending on the turner/header you go with you can't go wrong on a LS3 unless (i didn't look at his profile=LS?) except PL is FI and not NA. The OP will be NA/bolt on...so he thinks until the mod bug puts a smile on his face when he mashes the WOT button. So I hope this will not turn in to a header war or a "size" war.

oldmansan

There's no reason to think your numbers would be different with 1-3/4s. Powerlabs was putting down close to 600 rwhp and found no appreciable difference between 1-3/4s and 1-7/8s. That being said I don't think you can go wrong with either.

San

8850

The weight savings with 1 3/4 & 2 1/2" piping is probably worth the difference. Assuming you don't plan to add a bunch of power later. Kooks 1 7/8 & 3" piping is about 8-9 pounds savings over stock LS3. Bet you would get about another 10 pounds for almost 20 pounds savings over stock.

3 Z06ZR1

8850

You are obviously not a drag racer. There are drag racers that will pay hundreds of dollars for a 20 pound savings.

BaRcA4EvEr

thanks a lot guys

AndrewZPSU

Agreed. However if there is no difference between the two at that power level, one could assume that 1-7/8 inch headers would allow better flow at higher power levels. So why not opt for bigger in the chance of serious modification?

But I'm also not on the regular C6 Header. I'm using the C6 Z06 Header.... not saying that makes a difference either - its just what was in stock.

oldmansan

We agree to agree. I picked up some 1-3/4s locally for a great price but I'd have picked them up if they were 1-7/8s as well.

San

3 Z06ZR1

No way is going from 1 3/4 to 1 7/8 going to save 10 pounds
I was poking fun at silly statement. Powerlabs switch only involved
the primary switch 1 3/4- 1 7/8. Not the x pipe as he had 3 inch. With
both set-up's. I had 1 3/4 and 2 1/2 then switched to a z-06 header
1 7/8 with full 3inch. I changed 2 elbows out to make my intake hardpiped. Gained the dyno below. So 1 7/8 and 3 can add big
depends on the set-up. The ls-3 also flows more air than the ls-2
so it can use a little more flow. Go 1 7/8's for the ls-3!

8850

How do you know there is not 10 pounds difference? Have you weighed the two? Might want to save your sarcasm when you don't know what you are talking about before you call somebody silly.

3 Z06ZR1

Why would you think there is 10 pounds difference. Sounded silly to me!