LT Headers Question

[Rmitch223]

Ok, I'm getting ready to purchase a set of LT's from Calspeed, my question is should I run the 1 7/8" primaries or the 1 3/4" for my setup.
My currents mods are only a Custom Tune, Borla XR-1 and a Volant CAI. I plan to install a custom grind cam in about 6 months. Will the 1 7/8" primaries still be a good choice to run with the stock cam for awhile? or should I go with the 1 3/4"?

09 GMC Sierra Reg Cab 2wd
5.3L LY5

[Frenchy]

Do you have any ideas in mind for your cam? Or are you going to have somebody spec it, and just run with what they say? I'd go 1 7/8 (actually I DID go 1 7/8) because it gives room to grow. I think 1.75 is great for a stock engine, and for years that's what everyone ran simply because that's all that was available. With any cam worth installing 1 7/8 is the way to go. Followed by a good 3" pipe into a 3.5" or 4" single. Or true dual 3"

[Rmitch223]

I don't have any ideas on the cam spec yet.

So you think the 1 7/8" will be fine on a stock engine for awhile and not cause me to lose any power I would of had if I went with the 1 3/4"?

[Slowcrewcab]

Don't see why you would lose any power..... Still gonna have a muffler that should keep your back pressure sufficient. As frenchy said it gives you room to grow with out replacing them again...... Which you prob wouldn't want to do cause they can be a pain to install

[Duct_tape123]

Unless you're moving a lot of air through the motor(monster cam with aftermarket intake/heads and spinning to 7k+, or a good sized shot of nitrous) the 1-3/4" should take care of your needs. And you don't want any back pressure, you want velocity. Don't confuse the two.

[SLDPULR]

Ive got the 1 7/8 on my fairly stock truck and they are great

[Duct_tape123]

Pulled this out of my archived sites. May have been posted before, but its a good read.
http://www.superchevy.com/technical/...h/viewall.html
Mainly this explanation.
http://www.superchevy.com/technical/.../photo_04.html
Remember, most headers are measured as O.D. so you have to subtract the thickness of the tubing to get the I.D.
1-3/4" pacesetters are 16 gauge( ~.0598) so 1.75-.1196=1.6304"
Stock 5.3/4.8 heads flow roughly 160 CFM at .500, and around 175 CFM at .600
So the 1-3/4" pacesetter headers are pretty dang close for a stock headed motor.

[Rmitch223]

Thanks for those links Duct_tape123.
That was some great info. I think I'm gonna go ahead and go with the 1 3/4"...

[Rmitch223]

Has anybody had any fitment issues with Calspeed's LTs?

[BigMac]

yea but nothing I couldn't fix with a torch and a hammer...