thinking of headers

[bigdam99]

i am relatively new to fsc and this is my first post
ive got a 99 silverado z71 with a 5.3 vortech with true dual exhaust into two flowmaster 40 series mufflers, and a k&n 57 series (plastic runner tube) i like the sound it makes but it isnt quite loud enough.
i cannot decide if i want to go with shorty headers and keep the cats or go all out and spend the extra money to put long tubes on it, delete the cats, and get a performance tune so it will pass inspection
if i do go with the long tubes can any one predict how it would affect perfomance/ gas milage?

[Underpowered]

shorties are a wast on these trucks


if you want headers, get long tubes. they did not affect my fuel milage at all. power is better mainly up top, but i did not lose any low end.

my truck got ALOT louder with headers, loud enough where i had to change the rest of my exhaust to make it quieter, and before headers it was not quite as loud as i wanted.

[Turk09]

Here in New York State, we have emission laws. The long tubes won't cut it, hence the shortys are the only way to go for me. You read all the time that they won't help compared to the long tubed versions, and that may be correct. BUT!! They will still out preform the stock exhaust manifold by approx. 15-18hp. Maybe not as much HP gains as the long tube varieties, but a 15hp gain is worth it in my opinion.

[Underpowered]

Originally Posted by Turk09

Here in New York State, we have emission laws. The long tubes won't cut it, hence the shortys are the only way to go for me. You read all the time that they won't help compared to the long tubed versions, and that may be correct. BUT!! They will still out preform the stock exhaust manifold by approx. 15-18hp. Maybe not as much HP gains as the long tube varieties, but a 15hp gain is worth it in my opinion.

http://www.fullsizechevy.com/forums/...-shorties.html

read there. yes shorties are better than stock. but you do NOT get 15 HP from them. through most of the RPM rang you gain only 2-4 HP, with only a 4 HP peak gain

Long tubes provided over a 20 HP peak gain.

[Tweaks]

I remember that comparison thread and I liked everything about it except the they didn't use the same cat-back setup for the two different style of headers. Still, LT's will always be the best way to go for power if one is willing to modify the entire exhaust system and doesn't mind the added costs that go with it.

If you are just after sound and a slight power bump as a side effect is cool too, are on a budget, or have emissions testing, you're better off going the shorty route.

[Underpowered]

Originally Posted by Tweaks

I remember that comparison thread and I liked everything about it except the they didn't use the same cat-back setup for the two different style of headers. Still, LT's will always be the best way to go for power if one is willing to modify the entire exhaust system and doesn't mind the added costs that go with it.

If you are just after sound and a slight power bump as a side effect is cool too, are on a budget, or have emissions testing, you're better off going the shorty route.

things would have been more accurate if they had used teh same cat back, but they even mention that in teh article.

but also, that was on un tuned motors. with a tune, you would see great gains from both shorties and LT's, but the LTs would be more amplified of a gain with a tune.

[bigdam99]

thanks for all of yalls input i am on a budget but im still thinking of a complete exaust overhaul and going for long tube no cat but keeping my true duals and 40 series but adding a h pipe in there somewhere, and eventually get motor tuned out to pass emmisions

[para driver]

full headers are loud, plenty loud.. I have thought about going back to the standard manifolds..

[smokinsilverado]

As long as your state or city will allow you to go with LT's then that's what I would do. I can't so I got some shorties, they make a difference over stock, but it also depends on the brand you get.

[94_c/1500]

If were are worried about emmisions, then I would think removing the cats would make you fail.

[bigdam99]

it would make me fail
but i am planning on having my truck dyno tuned and they can tune it to where i dont need the cats to pass emissions
and what are some prefered brand of headers

[94_c/1500]

Hooker, Headman, Edelbrock, and Gibson are the ones off the top of my head. I am sure many more are out there.

Don't they look under the truck to see if you have cats? WV dosn't do emmisions testing, but they we have a safety inspection every year. We have to cats, unless you are friends with the guy (that dosn't always work either).

[bigdam99]

naa not here in NC they just test the exhaust gasses, you can take the cats off and as long as it passes the emission test its good to go

[94_c/1500]

You better hope you don't get caught on the street. More than likely you won't, but they can impound. At the very least a ticket. That is not a chance I am willing to take.

[Bum454ss]

Originally Posted by bigdam99

naa not here in NC they just test the exhaust gasses, you can take the cats off and as long as it passes the emission test its good to go

I'm down in Mooresville, NC? Would love to do this mod to my 99 5.7 suburban. Where did you get this info? I'm also under the impression that you must have cats to pass inspection. What shop are you having do the work? Can you give me the number so I can call them about my truck? Would be worth the drive to Raleigh to get it done right.

[bigdam99]

yea i was going off what my brother did and told me, i did some research of my own and realized that i was wrong sorry about that bad info, so you do need a cat.
i wanted to keep my setup legal so i geuss ill have to go with high flows or something
oooor i could still run no cats but gut 2 and weld them up there so it looks like i have some and still get it tuned so it would pass emission

[94~GMC]

I would just gut the cats and have them on there for looks.

[Markmx6]

Regarding Cats or not, every state is different as to what the emissions requirements are, and even in any particular state different counties may have different regs. Either way for it to remain legal (technically) you are not allowed to remove any emiisions device that was originally equipped on the vehicle, but as we all know its not illegal if you don't get caught...

In Arizona on 97 and later vehicles, and in my particular experience <--needs to be taken into account, They have not looked under my vehicle, they just test my fuel cap and plug in the scanner under my dash. As long as my check engine light (SES) functions and the computer has no codes, I pass.

Removing the cats will throw a SES due to the second set of O2 sensors (after cat) but I am willing to bet that there are custom tunes that can eliminate that from the computer.

[1CLNY2K]

Thats the same thing I am doing when I get longtubes is to just send my computer back in for a retune to turn off the rear 02 sensors and also turn off and delete the EGR. In MD they just test cap and plug you in. Most of them get scared when they have to operate a stick and just run it thru without touching it.

[94_c/1500]

Isn't removing the cats a $10,000 fine? I would get high flow cats and forget about it. Thunderbolts are good.