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Dual Plane Manifold differences. #1066493 08/31/11 01:26 PM 08/31/11 01:26 PM
Joined: Aug 2004 Posts: 1,047 Arizona 6 68CoronetRT OP super stock
68CoronetRT OP super stock 6 Joined: Aug 2004 Posts: 1,047 Arizona	I am trying to understand why some intakes have a solid bridge dividing the manifold and others have a "cut away" bridge and yet both are called Dual Plane Manifolds. Wouldn't the cut away bridge actually defeat the Dual Plane effect? Isn't it more of a Hybrid? Sorry if this is an elementary question for y'all but I don't get it.

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066494 08/31/11 01:41 PM 08/31/11 01:41 PM
Joined: Jan 2003 Posts: 7,861 Witness Protection Program Kudakidd master
Kudakidd master Joined: Jan 2003 Posts: 7,861 Witness Protection Program	This is a very old Mopar trick that goes back to the Edelbrock CH4B. I believe the purpose of the notch was to equalize the A/F mixture to each of the 8 cylinders.

Re: Dual Plane Manifold differences. [Re: Kudakidd] #1066495 08/31/11 02:38 PM 08/31/11 02:38 PM
Joined: Feb 2007 Posts: 2,578 sweden 1 1Fast340 master
1Fast340 master 1 Joined: Feb 2007 Posts: 2,578 sweden	may extend the rpmrange on plenumlimited manifolddesigns thats how i have been looking at it atleast.

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066496 08/31/11 02:46 PM 08/31/11 02:46 PM
Joined: Oct 2007 Posts: 4,207 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,207 New York	The divider notch is for idle quality, and it will be slightly larger for larger engines, etc. If you open the divider window size (by cutting the divider height down, partially or all the way to the floor level of the upper plenum) top end is improved (by sharing the plenums), but off-idle response and low RPM power will be down. The effects are proportionate to the old vs. new divider window X-area. Removed completely is inferior to a good single plane manifold since the largest window area is obviously much smaller than the plenum X-section. Boffin Emeritus

Re: Dual Plane Manifold differences. [Re: Kudakidd] #1066497 08/31/11 03:02 PM 08/31/11 03:02 PM
Joined: Jan 2003 Posts: 75,043 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,043 U.S.S.A.	Quote: This is a very old Mopar trick that goes back to the Edelbrock CH4B. I believe the purpose of the notch was to equalize the A/F mixture to each of the 8 cylinders. Don't forget the then available Holley 3 bbl carb ...

Re: Dual Plane Manifold differences. [Re: polyspheric] #1066498 08/31/11 06:03 PM 08/31/11 06:03 PM
Joined: Aug 2004 Posts: 1,047 Arizona 6 68CoronetRT OP super stock
68CoronetRT OP super stock 6 Joined: Aug 2004 Posts: 1,047 Arizona	Quote: The divider notch is for idle quality, and it will be slightly larger for larger engines, etc. If you open the divider window size (by cutting the divider height down, partially or all the way to the floor level of the upper plenum) top end is improved (by sharing the plenums), but off-idle response and low RPM power will be down. The effects are proportionate to the old vs. new divider window X-area. Removed completely is inferior to a good single plane manifold since the largest window area is obviously much smaller than the plenum X-section. Thanks for the replies and taking the time to help me try to get my head around this. I thought I read that the dual plane intakes provided a better idle and low end response? Also, is the "true" dual plane set up not really desirable then?

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066499 08/31/11 07:01 PM 08/31/11 07:01 PM
Joined: Oct 2005 Posts: 8,879 Ontario, Canada S Stanton Don't question me!
Stanton Don't question me! S Joined: Oct 2005 Posts: 8,879 Ontario, Canada	The dual-plane is essentially a cross between a single plane and a tunnelram - giving you some of the benefits of each but not the full benefit of either. Those funky intakes on late model cars are getting the best of both worlds by using a vaccuum control to alternate between the short runners and long runners based on load, rpm, etc..

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066500 08/31/11 08:37 PM 08/31/11 08:37 PM
Joined: Oct 2007 Posts: 4,207 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,207 New York	Read my article: http://victorylibrary.com/mopar/intake-tech-c.htm#dp Boffin Emeritus

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066501 08/31/11 08:48 PM 08/31/11 08:48 PM
Joined: Feb 2005 Posts: 4,316 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,316 Prospect, PA	Quote: I am trying to understand why some intakes have a solid bridge dividing the manifold and others have a "cut away" bridge and yet both are called Dual Plane Manifolds. Wouldn't the cut away bridge actually defeat the Dual Plane effect? Isn't it more of a Hybrid? Sorry if this is an elementary question for y'all but I don't get it. I cannot speak to all manifolds over time, or even of recent design, but years ago, most aftermarket dual plane manifolds had a notch at the rear butterflies, which I believe was to accommodate the Holly 3 bbl carb. On my 508, with considerable dyno testing, I found measurable and repeatable power improvements in playing with the divider on my 2D.

Re: Dual Plane Manifold differences. [Re: JohnRR] #1066502 08/31/11 10:25 PM 08/31/11 10:25 PM
Joined: Dec 2004 Posts: 10,555 Rittman Ohio fourgearsavoy I Live Here
fourgearsavoy I Live Here Joined: Dec 2004 Posts: 10,555 Rittman Ohio	Quote: Quote: This is a very old Mopar trick that goes back to the Edelbrock CH4B. I believe the purpose of the notch was to equalize the A/F mixture to each of the 8 cylinders. Don't forget the then available Holley 3 bbl carb ... Ding!!! we have a winner John I thought I was the only one that has set a three barrel carb on an old CH4B to see why they put the notch in there Gus 6804323-burnoutpicturegus.JPG (56 downloads) 64 Plymouth Savoy 493 Indy EZ's by Nick at Compu-Flow 5-Speed Richmond faceplate Liberty box Dana 60

Re: Dual Plane Manifold differences. [Re: polyspheric] #1066503 09/01/11 11:16 AM 09/01/11 11:16 AM
Joined: Aug 2004 Posts: 1,047 Arizona 6 68CoronetRT OP super stock
68CoronetRT OP super stock 6 Joined: Aug 2004 Posts: 1,047 Arizona	Polyspheric, Thanks for the article link. BSB67, When you say "playing with the divider" were you referring to milling a slot into it or closing it up? Last edited by 68CoronetRT; 09/01/11 11:17 AM.

Re: Dual Plane Manifold differences. [Re: 68CoronetRT] #1066504 09/01/11 10:05 PM 09/01/11 10:05 PM
Joined: Feb 2005 Posts: 4,316 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,316 Prospect, PA	Opening it up. There was no measurable loss of power from 3000 to 4000 rpm, and started picking up from there.

Re: Dual Plane Manifold differences. [Re: JohnRR] #1066505 09/01/11 10:09 PM 09/01/11 10:09 PM
Joined: Feb 2005 Posts: 4,316 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,316 Prospect, PA	Quote: Don't forget the then available Holley 3 bbl carb ... Ooops. Missed that you had already posted this.

Re: Dual Plane Manifold differences. [Re: BSB67] #1066506 09/01/11 10:15 PM 09/01/11 10:15 PM
Joined: Aug 2004 Posts: 1,047 Arizona 6 68CoronetRT OP super stock
68CoronetRT OP super stock 6 Joined: Aug 2004 Posts: 1,047 Arizona	That seems to be what I am reading. The gains on the cut away divider are in the higher RPM range. Well I need to study that article some more. Right now I am planning to stay with a full bridge dual plane and 1" 4 hole phenolic spacer to maintain separation. Street car so low end to 5500 should be mostly what it will see - unless I miss a gear. LOL Then the rev limiter will/should kick in.

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