Open headers or full exhaust? - Ford Muscle Forums : Ford Muscle Cars Tech Forum
FordMuscleForums.com is the premier Ford Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 05-27-2009, 03:35 PM   #1 (permalink)
Subscriber
 
Join Date: Mar 2007
Location: Jacksonville, FL
Posts: 173
Open headers or full exhaust?

I finally got my car running with the help of a local shop. I currently have open headers on a 331cid. He suggested I run full exhaust because I loose torque if I run only open headers. He said I at least need to extend the headers if not run mufflers. Looking for opinions
__________________
'91 Mustang Coupe(Drag Race Only), Scat 331 rotating assy, Mighty Demon 650,Vic. Jr heads, Vic. Jr Intake, Comp cam 579 lift., 4.10 gears
Best 1/4 mile E.T so far: "11.13@122"
jagfandaddy is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 05-27-2009, 03:50 PM   #2 (permalink)
Registered User
 
Join Date: Oct 2004
Location: Bethesda, MD
Posts: 1,564
Re: Open headers or full exhaust?

You will have to richen up your mixture if you run open headers. I run a 331 and have electrically controlled exhaust cutouts and on the street, you will lose torque as opposed to running a plain open header. This is from my experience. At the track though, I find opening my exhaust up I don't lose torque because I am running the car full throttle from the get go.
blown68 is offline   Reply With Quote Quick reply to this message
Old 05-27-2009, 03:57 PM   #3 (permalink)
Registered User
 
Join Date: Jun 2001
Location: 35.753983 N, 91.634603 W
Posts: 5,551
Re: Open headers or full exhaust?

You "might" "lose" a little torque going open. BUT, what you lose in low end you get back on the top end, generally speaking.

That said, with a properly designed exhaust system (from the headers back), it might gain a little torque AND top end horsepower. Such systems are few and far between it seems. I do know that a pair of single chamber flowmaster 3.5" race mufflers on mine drop .2 and 3 mph in the 1/8 mile even after jetting. It was quieter though. I just run them open. At least until they REQUIRE mufflers...or give an extra $50 or so incentive to the winner if they do have mufflers (like they used to).
__________________
GET OUT & VOTE THIS NOVEMBER!!
mavman is offline   Reply With Quote Quick reply to this message
Old 05-27-2009, 04:09 PM   #4 (permalink)
Subscriber
 
Join Date: Mar 2007
Location: Jacksonville, FL
Posts: 173
Re: Open headers or full exhaust?

That answered my question. Thanks! open It will stay.
__________________
'91 Mustang Coupe(Drag Race Only), Scat 331 rotating assy, Mighty Demon 650,Vic. Jr heads, Vic. Jr Intake, Comp cam 579 lift., 4.10 gears
Best 1/4 mile E.T so far: "11.13@122"
jagfandaddy is offline   Reply With Quote Quick reply to this message
Old 05-27-2009, 09:10 PM   #5 (permalink)
Registered User
 
Join Date: Apr 2002
Location: Merkel, Tx
Posts: 9,251
Re: Open headers or full exhaust?

Depends on several factors, but you need 10~16" of collector on those headers. You can be giving up 20+ HP running short little collectors.

Build about 20" worth of collector, draw a fairly thick line on them with crayon and make a pass - where the wax fries off, cut them there.

"Determining collector length
That's a great concept, but how do you know what length is just right for your race car? It might prove easier than you might imagine, but first, be sure to establish the primary-tube length. Once that's done, draw a thick line down the length of the collector using a crayon or grease marking pen. Make a normal hard pass with the car and check out the crayon mark. The temperature of the exhaust gasses within the collector will usually cause the mark to discolor or burn at a specific location on each collector. You can shorten the collector at this point. Just be certain to leave an inch or two of added material for further fine-tuning. It's tough to add material to the collector once it has been cut."
__________________
1967 Falcon 4 door 351C - 70 Mustang 351C
Owner built, owner abused.

Last edited by ckelly; 05-27-2009 at 09:19 PM.
ckelly is offline   Reply With Quote Quick reply to this message
Old 05-29-2009, 12:30 AM   #6 (permalink)
Registered User
 
Join Date: Feb 2004
Posts: 1,892
Re: Open headers or full exhaust?

In addition to the jetting the car may want more timing with open headers over a full exhaust.
__________________
65 mustang fstbk, pump gas street friendly Camshaft Innovations cammed .060 over 289, face plated T5. 11.12 at 122 mph and 1.53 60 ft all motor.
289nate is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Muscle Forums : Ford Muscle Cars Tech Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Jet changes for open headers versus closed exhaust blown68 All Ford Techboard 1 09-23-2007 02:20 AM
driving to exhaust shop w/ open headers....anything to worry about? dablack All Ford Techboard 17 12-04-2006 04:50 AM
Stainless headers & Full Exhaust 93-95 Lightning? Brand? dirtball All Ford Techboard 2 12-18-2005 05:59 AM
Exhaust -Full, Headers, Catback or What?? tsgman01 All Ford Techboard 2 07-02-2003 03:52 PM
full-length headers and exhaust installed erlong Galaxie Pages 4 08-13-2002 10:59 PM


All times are GMT -7. The time now is 07:34 AM.



Powered by vBulletin® Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.6.0
 

Garage Plus vBulletin Plugins by Drive Thru Online, Inc.