what headers with 408 and YSI?
 

I currently have lg long tubes, no cats, and magnaflow exhaust. I am making 788rwhp and my tuner and I were expecting higher with the parts used and boost levels. On the dyno graph it climbs hard until 6200 and then it just starts to level off. We are thinking that there is an exhuast restriction. My mods are in my sig. I want to get everyones opinion on change the exhaust to scoggin dickeys kooks 1 7/8 to 2" stepped headers with 3" x pipe and lg's 3" muffler system. We are thinking that I will drop maybe 2lbs of boost and still pick up power. I just wanted some input from others. The graph is posted in ls1tech in the dyno results section if needed.
Thanks for the help!
-matt

What size are the primaries on the LG headers you have? You have a serious amount of air to move... sick car!

ohh.. Kooks just released their 2" dia primary headers too.

https://ls1tech.com/forums/generation-iii-external-engine/769919-kooks-new-2-race-header.html

Try dropping the exhaust off from the headers back and see if that makes a difference, if you see a big gain doing that then you know you have an issue, if it only makes 5 to 10 rwhp, then I'd look elsewhere.

The lg's are 1 3/4. I was going to do the open header thing but the car is insanely loud to do that.

So like he said just run open headers for the dyno, see where it stands, and go from there. Driving open headers even on a stock motor is damn near unbearable :lol: Badass setup btw!

-J

I run open headers on my 402, 1 3/4 qtp's It didn't pick up a whole lot over the gutted catted Y and LM, it got to peak power a little earlier but that was about it. I did it because I was looking to lose some weight off the car, and seeing as it didn't hurt I am gonna run it that way, at least for the rest of this year. Track only car though.


I'd still drop the exhaust off on the dyno, see what it gets ya and go from there, it shoudl tell you if there's anythign to be gained by changing it.