Need exhaust pipe size recommendations
Thread Starter
Melting Slicks
Joined: Feb 2002
Posts: 2,699
Likes: 2
From: The Black Hole LA
Need exhaust pipe size recommendations
I am getting close to the point of putting this car back on the road and need to have a local exhaust shop fab a true dual set of pipes for me. I've had them do other cars in the past and they do good work and very resonable prices. I'm going to put an x-pipe on and need to know what size x-pipe to order to bring them when I have it done. I don't want to go to big becuase I've always read (could be misinformed here) that it will actually hurt power. Another consideration is I have a vert so the x-brace is a consideration.
The shop does not do mandrel bends and can do either 2.5" or 3"
Here are the specs.
383
SR intake
1.6 roller rocks
Dart Pro1 heads 2.02/1.6
219/219 cam
TPIS headers w/ 3" collectors
Auto trans
Compression should be around 10.7:1 best I can figure it
Haven't decided on Mufflers yet but most likely something simple with single inlet and single outlet. Suggestions on inlet/outlet sizes welcome too.
So I need opinions and reasons why as to which to go with: 2.5 or 3 inch.
The shop does not do mandrel bends and can do either 2.5" or 3"
Here are the specs.
383
SR intake
1.6 roller rocks
Dart Pro1 heads 2.02/1.6
219/219 cam
TPIS headers w/ 3" collectors
Auto trans
Compression should be around 10.7:1 best I can figure it
Haven't decided on Mufflers yet but most likely something simple with single inlet and single outlet. Suggestions on inlet/outlet sizes welcome too.
So I need opinions and reasons why as to which to go with: 2.5 or 3 inch.
Team Owner
Joined: Sep 2001
Posts: 62,162
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
2.5" will support it just fine, and you want the pipe diameter to decrease on the way to the back of the car to maintain flow velocity.
Thread Starter
Melting Slicks
Joined: Feb 2002
Posts: 2,699
Likes: 2
From: The Black Hole LA
Originally Posted by vader86
2.5" will support it just fine, and you want the pipe diameter to decrease on the way to the back of the car to maintain flow velocity.
Pro
Joined: Feb 2006
Posts: 688
Likes: 0
From: Concord NC
mine were stock 2 and a quarter now there 2.5 i believe. Vader knows his C4s very well so id def. listen to his advice. 2.5 seems approrpriate enough to keep the downforce and pressure for low end torque but wide/big enough to let out more gasses than the very restrictive stock exaust. If you did a complete Intake and Exaust upgrade, Gains are limitless headers, k&N, High performance MAF, Open lid, and mufflers. Improves sound "GAS MILEAGE" and power 
