The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > General Truck Forums > Racing and high performance (trucks haulin more than hay)

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 10-20-2020, 05:52 PM   #1
CARZ1968
Bowties from Birth
 
CARZ1968's Avatar
 
Join Date: Jan 2008
Location: Chester County PA
Posts: 86
3inch exhaust reduced?

My 99 c2500 came with 3inch exhaust to the muffler then it reduced to a single 3 inch exhaust. would switching to a dual 3inch outlet with dual 3 inch turndowns give me the best gas mileage/ performance? Should I add reduced turn downs (2.5 inch) instead of the 3"s? Looking to add a cold air kit, performance mass air flow and a program in the future.
__________________

68 K10 Burb aka "da bomb"
72 C10 SWB Highlander
97 30th anniv. Z28 Conv
99 Chevy Crew 454
11 Traverse AWD
CARZ1968 is offline   Reply With Quote
Old 10-22-2020, 08:33 PM   #2
HAULIN' IT
Registered User
 
Join Date: Dec 2015
Location: Beaver Falls, Pa
Posts: 122
Re: 3inch exhaust reduced?

The short answer would be: It would only help if the single 3" muffler guts/tail pipe are the restriction. If they aren't, you gain nothing.
Spending some time figuring/measuring the inside tubes & opening inside the muffler can be REAL eye opening! Quite often, the manufactures (even BIG well known companies) do all sorts of "cheats" where they use say, a 2 1/2" core in a whole group of mufflers & change just the ends that you see/attach to the pipes...not a problem for a guy with 2 1/4" exhaust or even 2 1/2", but if the engine really needs a 3" & the muffler has a 2 1/2" core area...pipes mean nothing at this point.
You would have to have a pretty nasty engine to need dual 3" exhaust. Also if you do, the words "gas mileage" wouldn't be something you would type very often. I guess I'll leave it at that. Lorne
HAULIN' IT is online now   Reply With Quote
Old 10-25-2020, 09:22 AM   #3
b454rat
Senior Member
 
Join Date: May 2004
Location: Binghamton, NY
Posts: 3,280
Re: 3inch exhaust reduced?

I had a similar truck like urs, had the dual 3" into the mufflers. Actually it had dual flow's on it, but i did true duals with i think 2 1/2" into the muffler, then dual 3" out the back. I don't think I gained anything, other than a good sounding exhaust.
b454rat is offline   Reply With Quote
Old 10-25-2020, 04:59 PM   #4
LS short box
Registered User
 
Join Date: Jun 2015
Location: Carlos MN
Posts: 526
Re: 3inch exhaust reduced?

I like to run 3" from the headers to a 3" muffler inlet. Then 2.5" tail pipes if room is limited. If you have the room I'd go 3" all the way.
I would go with an aftermarket mandrel kit or build it out of mandrel bend pieces. Muffler shop tubing benders really squish 3" tubing when they bend it.
LS short box is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 10:20 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Copyright 1997-2020 67-72chevytrucks.com