differences in ET/MPH full exhaust vs open exhaust - Chevelle Tech
Chevelle Tech join team chevelle as a supporting member  
Chevelle Parts at SS396.com      
GROUND UP & SS396.com         
Official Sponsor of Team Chevelle
     

Auto Insurance

Chevelles.com is the premier Chevrolet Chevelle Forum on the internet. Registered Users do not see the above ads.
Performance Our High Performance area

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old May 23rd, 10, 8:22 PM
curley8788 curley8788 is offline
Guest
 
Join Date: Apr 2006
Posts: 3,965
Default differences in ET/MPH full exhaust vs open exhaust

i have a feeling my exhaust is holding me back. i have a 2.5 inch system with an x pipe, ultraflows with full tails out the back. it is hand bent. i'm looking for a close to optimal exhaust setup and i am thinking of going to 3 inch with an x pipe dumped right before the rear axle. i havent run with open headers because after unbolting the exhaust there is no where for the exhaust to go as it rides up against my doughnut style gasket. if i push it down it scrapes up the gasket and the gasket is stuck to the collectors. i'd rather not break them.

i am trying to get some real world information on your cars with full exhaust vs open headers or exhaust that is real short or dumped. please give me your before and after ET/MPH.


where can i get a 3 inch system with an x pipe that dumps right before the rear axle as a kit?
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old May 23rd, 10, 8:32 PM
mino65 mino65 is offline
Team Member
mark
 
Join Date: Mar 2005
Location: connecticut,east haven
Posts: 1,649
Default Re: differences in ET/MPH full exhaust vs open exhaust

I just ran my car yesterday pypes 2.5in. x pipe race pros with tailpipes .11.75@113.With open headers 11.85@112.once.Mostly 11.90 -12.0s with the same system with street pros.
__________________
1965 malibu,03 silverado ss



M.J. 496
th350,3.73 3600lbs.
28x9 etdrags
New best of 10.30 1.41 60 ft.129.97mph
Reply With Quote Quick reply to this message
  #3  
Old May 23rd, 10, 11:01 PM
DragRacer DragRacer is offline
Lifetime Premium Member
Jason
 
Join Date: Sep 1998
Location: Highland Village TX, USA
Posts: 2,554
Default Re: differences in ET/MPH full exhaust vs open exhaust

Quote:
Originally Posted by curley8788 View Post
i have a feeling my exhaust is holding me back. i have a 2.5 inch system with an x pipe, ultraflows with full tails out the back. it is hand bent. i'm looking for a close to optimal exhaust setup and i am thinking of going to 3 inch with an x pipe dumped right before the rear axle. i havent run with open headers because after unbolting the exhaust there is no where for the exhaust to go as it rides up against my doughnut style gasket. if i push it down it scrapes up the gasket and the gasket is stuck to the collectors. i'd rather not break them.

i am trying to get some real world information on your cars with full exhaust vs open headers or exhaust that is real short or dumped. please give me your before and after ET/MPH.


where can i get a 3 inch system with an x pipe that dumps right before the rear axle as a kit?
Mike,

Back in the the late 90's on my old 383 SBC combo, I picked up 4 MPH in the 1/8th going from a 2.5" compression bent exhaust with 3-chamber Flowmasters to 3" home made mandrel bent exhaust (mitered and welded 90 deg. mandrel bends etc.) with 2-chamber Flowmasters. The car was running mid 11's at ~116 MPH at the time.

I've run 111.3 MPH in the 1/8th with 3.5" exhaust and 3" straight through design mufflers.
__________________
Jason Gore
AKA DragRacer
Naturally Aspriated 450 SBC - 915 HP / 714 lb-ft
3555 lbs
1.40 - 60', 6.18 @ 116.7 MPH - 1/8th
Reply With Quote Quick reply to this message
  #4  
Old May 23rd, 10, 11:28 PM
curley8788 curley8788 is offline
Guest
 
Join Date: Apr 2006
Posts: 3,965
Default Re: differences in ET/MPH full exhaust vs open exhaust

great info. i was thinking of reusing my 2.5 inch dynomax bullets on the end of the 3 inch system (with reducers of course) to cut cost. am i correct in assuming this will not affect performance?
Reply With Quote Quick reply to this message
  #5  
Old May 24th, 10, 1:51 PM
curley8788 curley8788 is offline
Guest
 
Join Date: Apr 2006
Posts: 3,965
Default Re: differences in ET/MPH full exhaust vs open exhaust

i called pypes and they said their x pipe kit puts the mufflers too close to the driveshaft so i cant use my bullet mufflers id need some offset mufflers. does anyone know of a kit that spreads the exit pipes out far enough to clear a large driveshaft
Reply With Quote Quick reply to this message
  #6  
Old May 24th, 10, 1:58 PM
trmnatr trmnatr is offline
Banned
Butch
 
Join Date: Nov 2007
Location: Maryland
Posts: 10,048
Default Re: differences in ET/MPH full exhaust vs open exhaust

the pypes kit with THEIR race mufflers
Reply With Quote Quick reply to this message
  #7  
Old May 24th, 10, 2:20 PM
curley8788 curley8788 is offline
Guest
 
Join Date: Apr 2006
Posts: 3,965
Default Re: differences in ET/MPH full exhaust vs open exhaust

id rather not buy new mufflers when all i need is the pipes to be spread apart a couple inches.
Reply With Quote Quick reply to this message
  #8  
Old May 24th, 10, 2:56 PM
sschevellefan sschevellefan is offline
Lifetime Premium Member
Anthony
 
Join Date: Sep 2004
Location: Citrus Heights, CA
Posts: 8,645
Default Re: differences in ET/MPH full exhaust vs open exhaust

summit and jegs both sell universal X pipe head pipes. Did you ever get your vibration fixed?
Reply With Quote Quick reply to this message
  #9  
Old May 24th, 10, 3:09 PM
Harold Sutton Harold Sutton is offline
Senior Tech Team
 
Join Date: Mar 2004
Location: Oologah, Ok.
Posts: 6,247
Default Re: differences in ET/MPH full exhaust vs open exhaust

Quote:
Originally Posted by curley8788 View Post
id rather not buy new mufflers when all i need is the pipes to be spread apart a couple inches.
More than likely your mufflers are the restriction. I have a friend who has a '70 Chevelle with a 450 h.p. - "502" and he did the small mufflers thing. It has always been a dog. Low 12s is the best it has ever run, he even changed to a bigger hydraulic roller trying to get it to run better, no luck. Still ran low 12s no matter what he did. It's a 4000 lb. slug. At about 110 mph it's done. Mustangs are blowing dirt in his face with regularity.
Reply With Quote Quick reply to this message
  #10  
Old May 24th, 10, 3:15 PM
MadmanMark MadmanMark is offline
Team Member
Mark
 
Join Date: Dec 2007
Location: Tampa, FL
Posts: 827
Default Re: differences in ET/MPH full exhaust vs open exhaust

I like to use http://www.torquetechexh.com/. They should be able to set you up with whatever you need.

When I went with their 3" x-pipe (over the axle and out the back), I had a 400-450hp 383 and the old system was a 2.5" muffler shop cheap job. At the time, all I changed was the exhaust and if I remember right, it was worth 0.3-0.5sec, but my old system had some nasty bends. I tuned the carb with open cutouts, but at the track it ran the same open or closed. On the highway, it got much better fuel economy with the cutouts open (2-3 mpg better).

I kept the exhaust for my current engine, which is in the 550-600hp range. Now there's a couple tenths and couple mph lost when I close the cutouts and the plugs seem to foul out faster. This could be somewhat due to the flowmasters, which probably weren't the best choice for performance.
Reply With Quote Quick reply to this message
  #11  
Old May 24th, 10, 3:34 PM
curley8788 curley8788 is offline
Guest
 
Join Date: Apr 2006
Posts: 3,965
Default Re: differences in ET/MPH full exhaust vs open exhaust

Quote:
Originally Posted by sschevellefan View Post
summit and jegs both sell universal X pipe head pipes. Did you ever get your vibration fixed?
i havent balanced the tires yet. i want to do this exhaust and that and go to the track before i restall this converter.
Reply With Quote Quick reply to this message
  #12  
Old May 24th, 10, 3:57 PM
Winston Wolf Winston Wolf is offline
Tech Team
 
Join Date: Apr 2010
Location: Minneapolis
Posts: 248
Default Re: differences in ET/MPH full exhaust vs open exhaust

I have a full 3" mandrel bent system, H pipe right after trans tailshaft and Dynomax mufflers. I have cutouts right off the headers. I have run it back to back open vs closed and it runs the exact same ET/MPH both ways. This is a 525 tq/475 hp SBC.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply
Chevelle Tech > General Tech Area > Performance      Current Topic: differences in ET/MPH full exhaust vs open exhaust
Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Chevelle Tech 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. Note, you will be sent a confirmation request to this address.
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.



Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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

Forum Jump


All times are GMT -4. The time now is 1:54 AM.


Is there a site like this for?    El Caminos Camaros Novas Impalas GTO Chevy Punch All Chevys

2009 Team Chevelle - AutoForums