How much hp will shorty headers add? And do they do anything for the sound????
Unfortunately, here in BC, we have to get an emission inspection every year, so cats have to stay on.

 

How much hp will shorty headers add? Not Much.

do they do anything for the sound? Probably not.

 

B&B, BASSANI and BBK shorty headers will add about 10hp by themselves, and you shouldn't expect much more.
You might appreciate more with a professional tune, but you'd have to decide if that additional cost is worth it. They have other advantages which most long tube users don't appreciate...#1 is that B&B is 50 state compliant!
There's no doubt that full length headers will gain you more, but they'll also come with more cost, more difficult installation, consideration of the annual emissions process, and most likely more involved changes to the rest of the exhaust system.
As to sound, that's subjective to each owner and dependent on what the rest of your exhaust system is.
Here's another current shorty header thread. You might ask those owners who've installed shorty headers for their opinion. That's what I've based my decision on. I don't have emissions requirements in my county, but it's coming at some point. I want ease of DIY installation w/o modifying the rest of my exhaust system. And I want the weight reduction (off the front end) over the cast iron oem manifolds. Saving weight is as good as more power.
http://forums.corvetteforum.com/c5-t...y-headers.html
Every time someone asks this question and gets replies from people who've actually had experience with them, they've said they noticed a slight change in the exhaust note, more so at WOT than at idle.
I recall most of those owners had some type of after market catback or the Z06 titanium catback. So, if you have an otherwise stock exhaust system, you may not notice any change in exhaust sound.
Do a search or search this forum (in the red banner) in C5 Tech using "shorty headers" as keywords. Some of the shorty header owners have gone so far as to get their cars dyno'ed after their DIY installation.
Imagine that, actual proof rather than conjecture...

 

hey how's it goin

i have shorty headers b& b tri flow on my 99 corvette. they didn't add that much of a sound. just barely louder. didn't really notice much performance wise.

i am currently running them on my 408 motor.. which i need longtubes. if you are interested in purchasing them i can let them go fairly reasonable. i also have electronic exhaust cutouts mounted after them. with them open.. very loud.. check it out. on my myspace

www.myspace.com/vettandtyphoon keep in mind the car is a 408 with a large cam

 

C5 99 corsa + bbk short headers (a friend of mine)
http://www.youtube.com/watch?v=ABt0y8KHgCE

my car (99 C5 ARH 1-3/4 + borla)
http://www.youtube.com/watch?v=Xfq2OCcjjGM