Looking to make 400HP NA 500HP with Nitrous. Wondering if I need a dual 3in setup or will dual 2.5in be enough??? Probably gonna be hedman 1 5/8in LT, Summit X-pipe, with ultra-flow bullut mufflers....

 

2.5 should be enough. That's what i'm running in my car and have no issues.

 

why 1 5/8 and not 1 3/4?

 

21/2" pipe will be plenty,but I'd go with 13/4" or even 17/8" headers

 

I used 2-1/2's on mine and they exspell everything nicely and I still have ground clearance. I chose 2-1/2's after about a month of studying the exhaust board here at thirdgen. I'm planning a 350-400HP n/a engine with 125 shot of nos.

Not to get off topic, but noticed you are running a cusotm XFI cam. I'm am also considering one of these. What lobes did you choose and at what LSA?

 

Anybody else beside hooker make a 1-3/4 primary LT header?

 

1 7/8's

 

1 5/8" headers should be good for 500HP i'd imagine, saw a back to back dyno run where A/F mixture was optimized on a 470ish HP motor and the only change was hooker 1 3/4" headers and headmann 1 5/8" headers, there was 15ft/lbs more torque with the smaller headers, and only a 4 or 5 HP gain in peak horsepower with the bigger headers, overall average curves were very close and didn't warrant the extra cost for a setup like myself or someone around that power range would warrant