Got the longtubes...now do I need 3" exhaust?
 

My longtubes should be here today and the 1 3/4" primaries collect at a 3" collector. Looking for opinions as to whether or not I should go 3" all the way back, only a 3" H/Xpipe, or just stay with the 2 1/2" Hpipe?

whatcha think?

what type of thought goes into exhaust size? I had heard that anything over 450HP needs 3", is this true (Cause I'm not making that much......yet)

If I just put the longtubes on and reduce them to 2 1/2", will I still get the power gains.

you should see some gains but if you dont have the money dont sweat it to much right now.

if you had a power adder i would say go 3 inch but unless your exhaust need replacing or you have the money it will work fine for now.

I have a 2.5 h pipe that im going to replace it , It work's fine on the street with low boost 8lbs but at the track i unbolt it I've been told its to small but i dont have the money to change parts that arent broken.

I will be getting a 3" x pipe with 3" muff's that exit before the rear wheel's when I have the money or need to replace the exhaust. the hard part will be the turbo outlet which is 2.5"

That's a good point that I didn't articulate. I really don't want to "fix what ain't broke". I would much rather connect the longtubes to my 2.5" H-pipe and mod the h-pipe to accept the 3" collector (or vice versa) than to throw more cash that I don't have around. I'm just looking to help her breathe a bit more using the longtube setup and maybe gain some MPH while at it.

Generally speaking, how do you know when it's time to go 3"? I always thought the ol big block had 3" exhausts, and anything around 450-500 HP needed it. But with a 393 ci small block making appx. 400 HP, do I really need to fix what ain't broke? I guess you're telling me to save the bucks.....which sound great to me.

I wouldnt sweat it yet. You probably would make a few more ponies with 3 inch exhaust but not enough to justify the cash that would go into it.

My 2 cents,

why are you only running 12.68 @ 105 mph with a 393? Are you still tuning? Your car should be faster than that.