09 Sierra 6.2 1 3/4 vs 1 7/8 Headers
 

Hi there I have a 09 Sierra 6.2 Denali AWD and currently have the mods listed below. Just wondering what kind of hp and tq would I gain going to 1 7/8 Headers and 3 inch collector. Thanks

Afe Stage 2 Si Intake
LS7 90mm Throttle Body
Corsa Touring Cat Back
OBX 1 3/4 LT Headers 2.5 inch Collector with Cats
Diablosport Intune Custom Tune by DiabLew

You won't gain much...money would be better spent on a cam upgrade, nitrous, converter, or 4.10s....

I disagree, OP you might might around 8-15rwhp more with the 1 7/8s plus gives you room to grow when you do a cam. Heck my buddy gain 11rwhp out of a NNBS "5.3L" doing the swap.

The bigger headers are better on that engine for sure... But not worth the money to swap right now. It is better spent elsewhere... If it comes time to make big power then swapping headers will be one of the smallest hurdles to get past.

I'd do a converter first .

Converter next, and a cam after that. Then if you still want a little more, 1 7/8" headers.

What about power say under 3500 rpm? Like ur DD power haha? Which would be better with high flow cats then straight through muffler. (1 7/8"or 1 3/4")

Although i dont frequent the site I have friends who do and over at camaro5 and there are back to back tests with 1 3/4" vs 1 7/8" headers. The differences were minimal at best

Even 2" prims havent shown huge gains unless you have big cubes? Spend money elsewhere

Heres a thread from tech

1 3/4 headers vs 1 7/8 headers my experience - LS1TECH

I have the same mods and have nitrous. It's OK, but I wasn't that impressed. I did fry my converter though, so i put in a Circle D tripe disk at 2600. I'm happy with that. It seems a little loose, but when i get my cam in there it won't. My truck is a DD and I do tow 8,000 Lb on occasion. Forget the expensive 1 7/8" header and get yourself a converter and cam with a good dyno tune.

A converter is your next best performance supporting mod and will give a noticeable driveability difference. Then you are prepared when the cam and blower or spray time comes and it will.

1 7/8 may gain you some at the high end of WOT but really it's a truck how often does full WOT every last pony performance come into play in a DD scenario unless you are racing the truck.

Whats the best converter for my truck also will I gain anything with no cats and how much louder would it be with my mods. Thanks

Chris at Circle D build mine based on what I do with my truck. I opted for the triple disk, because I am throwing nitrous at it and plan to beat on it.

whats your peak torque? once you know this you'll know what converter to get ;)

get the headers then cam then stall to match after dyno!

skeet knows his stuff :thumb:

i cant give exact advice on the 1 3/4 vs 1 7/8 bc i dont have track numbers to back it up due to changing combos an not being tuned yet.

mine traps 105.5 to 107.9 with the 1 3/4" ill know how it does jan 30th though on the dyno

Seeing as how you are not FI, I doubt you would notice a gain from the header swap. I definitely think the larger primaries would be a mistake, as your exhaust port is significantly smaller than 1 7/8". Any time air flows into a significantly larger opening, it loses velocity. The other members seem to have the right idea about focusing on other mods. Good luck!

Edit: Post is way older than I thought lol!

Converter!

Although I say converter first, then cam, you have to keep in mind the cam you have spec'd will rely on your exhaust as well. You need to decide if you're staying at 1 3/4 or eventually going up to 1 7/8", that will determine what your cam should be ground at.

What is your end goal and purpose? You may find the 1 3/4" will suffice long term for you and you can put the $ to converter, cam & springs.