Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

I6 header or header(s)? 6-1 or 6-2

General engine tech -- Drag Racing to Circle Track

Moderator: Team

MrWOT
Pro
Pro
Posts: 289
Joined: Sun Feb 17, 2008 4:54 pm
Location: Boulder Creek, CA
Contact:

I6 header or header(s)? 6-1 or 6-2

Post by MrWOT »

A 6-1 design is simpler, easier to route, lighter and has less surface area to lose heat to than a 6-2.

The 6-2 would allow for 120* spacing between exhaust pulses, and the use of an h/x pipe.

Seeking the broadest curve possible, is there an actual advantage to the 6-2, or is it far outweighed by the weight? :wink:
preston meyers
New Member
New Member
Posts: 43
Joined: Tue Apr 01, 2008 1:45 am
Location:

Re: I6 header or header(s)? 6-1 or 6-2

Post by preston meyers »

MrWOT wrote:A 6-1 design is simpler, easier to route, lighter and has less surface area to lose heat to than a 6-2.

The 6-2 would allow for 120* spacing between exhaust pulses, and the use of an h/x pipe.

Seeking the broadest curve possible, is there an actual advantage to the 6-2, or is it far outweighed by the weight? :wink:
I have no input other than I'd like to know myself as I've never seen a clear cut answer
Live everyday as if it's your last, learn everyday as if you will live forever.
Creech

Post by Creech »

I think it depends where the power band is. On a 800ci pro stock you'll see 2-2-1. On a 500ci they don't vary to far off the conventional header.
strokersix
Pro
Pro
Posts: 385
Joined: Sat Aug 23, 2008 7:12 am
Location:

Post by strokersix »

Anyone have a photo or link to a 6-3-1 header? I'd love to see it.
dwilliams
Guru
Guru
Posts: 1131
Joined: Sun Oct 15, 2006 10:00 am
Location:

Post by dwilliams »

An inline six works out as two 120-degree triples. You treat 1-2-3 and 4-5-6 as separate groups.

An even-firing three is as simple as headers get - just pull the three pipes together at some convenient point and run the exhaust out. No collector necessary, since there's no overlap between cylinders until the exhaust duration goes over 240 degrees.
W. Tripp
Expert
Expert
Posts: 574
Joined: Thu Apr 10, 2008 8:28 pm
Location: Birmingham, AL, USA
Contact:

Post by W. Tripp »

dwilliams wrote:An inline six works out as two 120-degree triples. You treat 1-2-3 and 4-5-6 as separate groups.

An even-firing three is as simple as headers get - just pull the three pipes together at some convenient point and run the exhaust out. No collector necessary, since there's no overlap between cylinders until the exhaust duration goes over 240 degrees.
+1

The 240° separation is a great advantage when working on inline 3s and 6s. Inline engines are more sensitive to primary length and pulse interaction than V engine designs, where collector length sensitivity is more of an issue.

This separation also makes tuning intake systems easier, and very effective.

Fitting 2 separate 3-1 headers, running dual exhaust and setting collector length with a termination box has advantages that need to be considered.
User avatar
exhausted
Guru
Guru
Posts: 1225
Joined: Mon Oct 29, 2007 9:07 am
Location: Matthews, NC

Post by exhausted »

I usually use 6-2-1. Do not see the need to go 6-3-1 as they are still even pulsing and heavier and more mass to fit. It does depend though, I suppose there are situations where it would be harder to package the 3into1 collectors.
I also keep the primary lengths less than 2/3rds of total OAL. Even shorter for drag stuff. :)
Calvin Elston
Elston Exhaust
Matthews, NC 28104
346-704-4430
Blog: www.exhausting101.com
MrWOT
Pro
Pro
Posts: 289
Joined: Sun Feb 17, 2008 4:54 pm
Location: Boulder Creek, CA
Contact:

Post by MrWOT »

Well, guess I'll pipemax for 6 cyl and zoomies then, termbox and exhaust separately. Great input all :)
Circlotron
Expert
Expert
Posts: 983
Joined: Tue Feb 05, 2013 6:56 am
Location: Melbourne, Australia

Re:

Post by Circlotron »

strokersix wrote: Sat Jan 24, 2009 6:36 pm Anyone have a photo or link to a 6-3-1 header? I'd love to see it.
Factory fitted to 84-86 Holden VK Commodore with EFI option.
You do not have the required permissions to view the files attached to this post.
chevyfreak
Pro
Pro
Posts: 403
Joined: Sat Oct 04, 2014 4:23 am
Location: south africa johannesburg

Re: Re:

Post by chevyfreak »

Circlotron wrote: Sat Nov 07, 2020 11:42 pm Factory fitted to 84-86 Holden VK Commodore with EFI option.
Thanks for sharing.
About 2years ago i built my own header/extractor (here in south africa its being called " branches ") wanted to do 6-2-1 but my luck at that time i could not find 3into1 collectors locally, so then came the idea of doing 6-3-1 but still needed a 3into 1 collector, and space not that much so i made a 6into1 but the shape is not round, made it rectangular. Building an unique collector, being a pita but got it done, not one of my best attempts of building my own.
Chevy inline six in an opel a2 senator, which is very close to the holden vk commodore, just that it uses a steering box with draglinks instead of rack system like the holden. So space not that much with chevy bellhousing getting in the way.
I see they use very long primaries,
mine less than half that lenght so there is only one pipe going inbetween draglink and bellhousing.
Works great for space constraints but at low cruising rpm 1500-2000rpm doing 60-80kph it sounds like a damn subaru with that constant misfire popping.
Changed back to std log manifold cleared that. (I'm not very fond of a boxer sound) as for performance, normal driving there is no difference, above 4000rpm it does help if engine is cammed.

Chevy freak.
Bowtie for life
Circlotron
Expert
Expert
Posts: 983
Joined: Tue Feb 05, 2013 6:56 am
Location: Melbourne, Australia

Re: I6 header or header(s)? 6-1 or 6-2

Post by Circlotron »

Found another, aftermarket this time. For same motor retrofitted to earlier car that originally had earlier 9-port head. https://genieheaders.com.au/listings/ht-hz-gen099e/ Usually feeding 3 cyls to each pipe excites a resonance in the entire length of the pipe, making it really bark at mid rpms. I wonder what a *triple* exhaust out the back would have sounded like? :D
You do not have the required permissions to view the files attached to this post.
chevyfreak
Pro
Pro
Posts: 403
Joined: Sat Oct 04, 2014 4:23 am
Location: south africa johannesburg

Re: I6 header or header(s)? 6-1 or 6-2

Post by chevyfreak »

Circlotron wrote: Sun Nov 08, 2020 5:49 am I wonder what a *triple* exhaust out the back would have sounded like? :D
Haven't tried that one, but it can be done just to confuse some people. Or maybe 6 singles , 3 per side. really confuse them all :lol:

Have done the dual setup, no balancing between them it sounds the same as my essex (english) v6 in my cortina.

Chevyfreak.
Bowtie for life
BCjohnny
HotPass
HotPass
Posts: 1122
Joined: Sun Feb 26, 2006 6:07 pm
Location: England

Re: I6 header or header(s)? 6-1 or 6-2

Post by BCjohnny »

In the vast majority of cases the 6 - 2 -1 set up, split 1 2 3 - 4 5 6, has been proven to work the most capably

I'm sure someone can dredge up a exception, but it doesn't disprove the rule

Keep the pipe sizes, especially the primaries, on the conservative side :wink:
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon
User avatar
panic
Guru
Guru
Posts: 2013
Joined: Sat Dec 11, 2004 12:04 pm
Location: Ecbatana
Contact:

Re: I6 header or header(s)? 6-1 or 6-2

Post by panic »

6-3 not only joins pairs with uneven firing order, but different order depending on which pair.
1 & 2 are 240-480-240, 3 & 4 are 360-360, 5 & 6 are 480-240-480
BCjohnny
HotPass
HotPass
Posts: 1122
Joined: Sun Feb 26, 2006 6:07 pm
Location: England

Re: I6 header or header(s)? 6-1 or 6-2

Post by BCjohnny »

Ok ..... the assumption being a 153624 firing order, which is the most common ....... :wink:
"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon
Post Reply