3.5" dual exhaust
#1
Senior Member
Thread Starter
Join Date: Mar 2007
Location: Muscatine IA
Posts: 574
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Firebird Formula
Engine: 383
Transmission: built 700r4
Axle/Gears: 4.11, 9inch
3.5" dual exhaust
just like the title says looking for some people that have run 3.5" dual exhaust. specifically in the area around the front inner subframe. also going around a th400 trans mission. plan on building an custom crossmember to give me as much room as possible.
and before it gets said yeah im going to need some big pipe down there to allow a 540 bbc to exhale. as much as I like the idea of dumping the exhaust out the fenders im not sure how much ill like that on the street.
and before it gets said yeah im going to need some big pipe down there to allow a 540 bbc to exhale. as much as I like the idea of dumping the exhaust out the fenders im not sure how much ill like that on the street.
#5
Supporter/Moderator
iTrader: (7)
Join Date: Feb 2001
Location: Cincinnati, OH
Posts: 13,247
Likes: 0
Received 391 Likes
on
298 Posts
Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Re: 3.5" dual exhaust
What kind of power will you be making? You might have to live with a dual 3" and plan on running cutouts when you need the full "go".
The following users liked this post:
427seven (08-21-2019)
#6
Supreme Member
Re: 3.5" dual exhaust
Oval is about your only good choice around the trans. you can go back to round after.
You also might want to consider a relocated panhard bar
https://www.foundersperformance.com/...v=7516fd43adaa
You also might want to consider a relocated panhard bar
https://www.foundersperformance.com/...v=7516fd43adaa
#7
Supreme Member
iTrader: (20)
Re: 3.5" dual exhaust
The problem is getting a longtube collector of 3.5-4” with right length and transition to oval by the crossmember. Theres not enough room if you have a big auto trans. Maybe with a t56 or something. I’m not sure.
But on mine with custom fabbed headers i can fit a 3.5” collector with good clearance but have to transition quickly to 3”
Trending Topics
#8
Supreme Member
Re: 3.5" dual exhaust
You can also make your own oval pipe with some 2x4s and a hydraulic press
#9
Senior Member
Join Date: Jan 2019
Posts: 571
Received 482 Likes
on
233 Posts
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: 3.5" dual exhaust
you should look very closely at what the actual gains would be, going from 3" to 3.5", after you do all the mods are you gonna get 10hp? 20? yer gonna have to do a lot of testing to maximize, that costs mucho $. If you have a full drag setup, you wouldn't have to worry about room, so I'm assuming the suspension hasn't been changed much. All that torque is not going to be accommodated by the suspension, so you gotta ask yerself, what is it for? so you can bench race? or just sit and haze the tires? If it's to make noise, get the cutouts, you can make 3" fit well.
#10
Supreme Member
iTrader: (20)
Re: 3.5" dual exhaust
On a healthy 540 bbc I suspect gains will be pretty healthy. I kinda want to test it on my own 555 as so far the power numbers seem low.
On a 14:1 comp 540 that was making north of 850 flywheel saw 40-50 hp on open 4” headers vs full dual 4” exhaust with mufflers
I have seen 20’s whp on some muffler deletes on late model cammed ls3 stuff. I think the gains are there to be had
On a 14:1 comp 540 that was making north of 850 flywheel saw 40-50 hp on open 4” headers vs full dual 4” exhaust with mufflers
I have seen 20’s whp on some muffler deletes on late model cammed ls3 stuff. I think the gains are there to be had
#11
Senior Member
Thread Starter
Join Date: Mar 2007
Location: Muscatine IA
Posts: 574
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Firebird Formula
Engine: 383
Transmission: built 700r4
Axle/Gears: 4.11, 9inch
Re: 3.5" dual exhaust
based on my math im going to need the 3.5 stuff. shooting for 750hp at the crank. suspension is stock style but all tubular also the torque arm will be a little more out of the way its a Midwest 9" with his third gen arm. headers will be custom as well so that should help with collector location. main purpose for the build is drag week and I want to be competitive in street machine eliminator. hence bbc/th400 bracket car lol. it doesn't see much street time but it is nice to not worry about dragging exhaust when loading and unloading from the trailer.
seeing orr's pictures makes me think down and forward out the fenders really might be my best bet.
seeing orr's pictures makes me think down and forward out the fenders really might be my best bet.
#13
Senior Member
Thread Starter
Join Date: Mar 2007
Location: Muscatine IA
Posts: 574
Likes: 0
Received 2 Likes
on
2 Posts
Car: 91 Firebird Formula
Engine: 383
Transmission: built 700r4
Axle/Gears: 4.11, 9inch
Re: 3.5" dual exhaust
im not sure theres room for a cut out there. I could find room for them with my small block and hooker long tubes with out hitting the frame.
Thread
Thread Starter
Forum
Replies
Last Post
F-Body Demon
Exhaust
16
07-29-2008 07:53 PM