how do bends affect header length? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 02-27-2007, 02:02 PM
Member
 
Last photo:
Join Date: Aug 2005
Location: Canada - brrrrr
Posts: 122
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
how do bends affect header length?

I'm working with a v6. The books call for 36" primaries. But, one side of the engine is really cramped and I need to put in at least 3 bends to make it fit. (The other side is no sweat)

I have an initial 70* on all 3 pipes, then the second bend which varies between 90* up to 180* on a 2" radius , followed by 2 - 90*s on a 3" radius. It's all pretty tight until it goes to the collector, which is a Shoenfeld.

We're talking pretty much a backwards "S" shape on #5 cylinder vs. a kind of "d" on #1.

So the question is how much length changes with, say, a 90* bend vs. a 180* bend, etc. Does anybody have some good data on this?

I can either shorten or lengthen to suit.

Thanks for the help,
Arn

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 02-27-2007, 02:24 PM
Member
 
Join Date: Dec 2004
Location: Madison, WI
Posts: 1,885
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Although it is almost impossible in some cases we try and make all the tubes the same length, without any account for flow restrictions due to the bends. Although I am sure there is some loss with bends the total length of tubing is SOOO short in the grand scheme of things its not worth going to the 4th decimal in calculating it out. For complex jobs just trying to get tubes within an inch or two of each other is a major endeavor. Concentrating on the correct primary tubing size and length, plus collector length is where we find the most gains on the dyno.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 02-27-2007, 02:29 PM
Member
 
Last photo:
Join Date: Aug 2005
Location: Canada - brrrrr
Posts: 122
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks

Yeah, I hear you.

Some local guys have sort of said the same thing to me. The reason I am asking is that the one side is sort of like spaghetti if you get my drift.

I'm still curious if there is any research on it.

Thanks,
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 02-27-2007, 03:32 PM
chrisflock's Avatar
Member
 

Last journal entry: A quick trip
Last photo:
Join Date: Jun 2004
Location: wisconsin
Posts: 170
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I don't recall where, but I read a project log where a guy actually flow-metered a variety of tubing of different diameters with different bends, and the results he got were a little surprising, but basically what it came down to was that bends were far less important than the length and diameter. If the bend changes the cross sectional area of the tubing, that will make a big difference because it is effectively dropping the diameter of the tubing, but otherwise he found that the overall length of the tube was a much bigger factor. Like, the difference between a straight tube 4 feet long and the same diameter tube coiled up (again, this was mandrel bends or what not, so the overall diameter stayed the same) was only a few %.

Anyway, I'm sure that Google would yield some technical papers on the subject that would probably turn your BRAIN into spaghetti...
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 02-27-2007, 04:19 PM
Member
 
Join Date: Dec 2004
Location: Madison, WI
Posts: 1,885
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Spaghetti is putting 2" equal length headers in a 70 Camaro stock stub car with AC while trying to maintain sparkplug and starter clearance. So yeah, I got your drift what it's like, a nightmare.

I'm sure as Chris mentioned there is data out there and if I got out my fuel gas code book I could give you some data on the losses per bend type. BUT, after being in mechanical engineering for 20 years the losses versus the actual mass flow and tubing length make it a pretty mute issue.

I worked with Bruns, Stahl, and others redoing a set of stainless headers on my car this past winter. I fabbed them up from the flanges out. All the time was spent on tubing diameter, lengths of steps (I step sized this set) length of primaries and collector design and length. No matter how you get there with the bends and folds in the pipe lengths the key was trying to keep them as equal as possible. In my case that was trying to be within a couple of inches.

Schoenfeld are great folks and we work with them all the time on the circle track stuff. They know their stuff and their headers make power. They would be my guiding light for any questions you have as you get more into it.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 02-28-2007, 07:46 AM
Member
 
Last photo:
Join Date: Aug 2005
Location: Canada - brrrrr
Posts: 122
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks again

Thanks guys.

That is really good advice. You've answered my question really well.

I am doing up mine from the flange out as well. I have laid out the bends on plywood, and, using copper wire 36" long, I've been able to lay out plans that are very close, and likely within 1/4 to 1/2" of being the same across all 6 pipes.

I'm using Schoenfeld slip on collectors and a custom laser cut flange. They should be nice if I don't screw up.

Arn
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 03-03-2007, 06:50 AM
Crazy Mopar Guy's Avatar
Member
 
Last photo:
Join Date: Dec 2003
Location: HotRodCity, Canada
Posts: 456
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I made my own headers and wondered the same thing- one side looks a little bit on the "spaghetti" side.

In something that is low velocity with not much force behind it, I think the bends in the pipe would come into play more, as the static pressure difference would affect the two types of pipe greater- straight versus bends.
The more I tlked to header guys, the more I came to the conclusion that there is so much force in such a little distance, that the primary diamter and length were more important than the bends, so I went with diameter and length.

Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 03-03-2007, 06:52 AM
Crazy Mopar Guy's Avatar
Member
 
Last photo:
Join Date: Dec 2003
Location: HotRodCity, Canada
Posts: 456
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
passenger side
Attached Thumbnails
Click image for larger version

Name:	p****ide.jpg
Views:	47
Size:	85.8 KB
ID:	19004  
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 03-04-2007, 11:27 AM
Member
 
Last photo:
Join Date: Aug 2005
Location: Canada - brrrrr
Posts: 122
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Nice headers

Very nicely done and thanks for the info.

I just wish I could weld as nicely as you obviously can.

Arn
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last 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
Header Painting How To Full Throttle Engine 33 03-08-2006 01:06 PM
Close fitting, full length SBC header recommendation PatM Hotrodding Basics 7 11-20-2004 10:48 PM
header length reversion waves masonmachines Engine 2 08-04-2004 07:10 PM
exhaust system length affect performance? smlblcks10 Engine 10 02-19-2004 04:40 PM
Header leak help tm454 Engine 2 12-18-2003 10:53 PM


All times are GMT -6. The time now is 05:20 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.