I have a 2003 chevy silverado rcsb that currently has the 5.3. Came across a lq4 with 100,000 miles so i picked it up. Parts list i have for it is Texas Speed PRC 2.5 heads with 58cc combustion chamber with double springs for .650 lift, comp cam part number 54-438-11 ( specs are 227/235 @ .050 .614/.621 lift, holley hi ram 92mm intake, air raid cold air intake and ebay obx long tube headers, 42 lb injectors, performabuilt level 2 4l60 with yank 3600 stall, detroit tru trac with 4.10 gear and dynotune nitrous setup (planning to spray 150). Any thoughts or estimates for this setup? Thanks

 

Save your money on the hi-ram. There isn't enough cam for 8000 rpm.

Get a nnbs intake instead.

My guess is 380-410 on motor and around 520 on spray. Give or take.

 

And dump the **** obx headers.
Speed engineering are better as they are closer to equal length primarys and even tho not the best collector, still light years better than the obx kaka.
Go,with the 1 7/8 primarys.

If you want, have the nnbs intake ported by the site sponser here, forgot name atm.

 

I'd keep the headers if you have them. 1-7/8 primaries are not going to help that much. And it will all be at the very top of the power band.

I made good power with pacesetter 1-3/4" headers.

X2 on the 90 mm truck intake.

I'd guess closer to 380. Those gears will eat some power. Trap speed is going to the real story of what kind of power you're making.

 

He has a 6.0 with ported heads and a high lift cam, the 1 7/8 will make more power everywhere over 1 3/4 headers.

 

I've already got the headers and Holley hi ram intake. Will I be giving up low rpm torque compared to the nnbs intake vs the Holley?

 

Almost certainly.

 

Hoteod mag, ls intake comparison
Just remember the tbss and nnbs teuck manifold are the same.

20 LS1 Intake Manifolds: Tested! - Hot Rod Network

 

Cathedral port, 90mm truck intake is the best stock option you have.

What are you doing for a fuel pump? You'll need to figure out the fuel rail setup with any intake you go with.

 

There os both return and non return nnbs truck intakes.