Re: Dual Plane Manifold differences.
[Re: 68CoronetRT]
#1066496
08/31/11 02:46 PM
08/31/11 02:46 PM
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Joined: Oct 2007
Posts: 4,210 New York
polyspheric
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New York
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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
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Re: Dual Plane Manifold differences.
[Re: Kudakidd]
#1066497
08/31/11 03:02 PM
08/31/11 03:02 PM
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Joined: Jan 2003
Posts: 75,088 A Banana Republic near you.
JohnRR
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I Win
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A Banana Republic near you.
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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 ...
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Re: Dual Plane Manifold differences.
[Re: polyspheric]
#1066498
08/31/11 06:03 PM
08/31/11 06:03 PM
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Joined: Aug 2004
Posts: 1,047 Arizona
68CoronetRT
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Arizona
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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?
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Re: Dual Plane Manifold differences.
[Re: 68CoronetRT]
#1066501
08/31/11 08:48 PM
08/31/11 08:48 PM
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Joined: Feb 2005
Posts: 4,318 Prospect, PA
BSB67
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Prospect, PA
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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.
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Re: Dual Plane Manifold differences.
[Re: polyspheric]
#1066503
09/01/11 11:16 AM
09/01/11 11:16 AM
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Joined: Aug 2004
Posts: 1,047 Arizona
68CoronetRT
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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.
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Re: Dual Plane Manifold differences.
[Re: JohnRR]
#1066505
09/01/11 10:09 PM
09/01/11 10:09 PM
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Joined: Feb 2005
Posts: 4,318 Prospect, PA
BSB67
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Quote:
Don't forget the then available Holley 3 bbl carb ...
Ooops. Missed that you had already posted this.
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