Intake manifold center rib notch....why?

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67dartgtgo

67dartgtgo

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Ok....why is it on some dual plane intake manifolds the center rib is notched at the carb flange and on some manifolds it remains in tact to the top of the flange with squared corners. Any benefit to the notch and can porting it make any difference?
 
C4A48F09-2322-494D-BE25-3C1694FE46EB.jpeg
 
Equalize the draw signal without affecting the wet flow?
 
That's just a plenum divider. Like the old LD4B's that had a full divder, someone figured out you could increase performance at higher rpms if the divider was modified.
 
I've been doing some reading on this as I have been trying to decide what intake to go with. From what I have read, it is to allow a little mixing so the right side of your carb isn't ONLY feeding the right side of the motor, and vice versa. I think it is intended to let the motor scavenge a little fuel from each side of the carb flow if needed. Kind of like a small compromise of dual plane and single plane.

Just what I've read....
 
I have an air gap with the full plenum divider and just wondering what if any changes might be seen by doing this.
 
Thanks Mike. That’s exactly the info I’d been looking for.
Thanks to MRL Mike as well...great thread.
Also looks like you don’t need very much reduction from the height. .250” is pretty easy to do at home with no cash out.
 
its to give you some benefits of a single plane. everything is a give or take
 
67dartgtgo said:
Thanks Mike. That’s exactly the info I’d been looking for.
Thanks to MRL Mike as well...great thread.
Also looks like you don’t need very much reduction from the height. .250” is pretty easy to do at home with no cash out.
Click to expand...
You bet. Mike retired from the Mopar engine building gig a while back. He is missed but the knowledge he shared still benefits us all. Great guy. Hope he and his family are doing well. He hasn't been around since January. Maybe he will stop in to say hello. @MRL Performance
 
If you want to see if it helps you put a 1/4 open carb spacer on it.
 
Frnknsteen said:
I've been doing some reading on this as I have been trying to decide what intake to go with. From what I have read, it is to allow a little mixing so the right side of your carb isn't ONLY feeding the right side of the motor, and vice versa. I think it is intended to let the motor scavenge a little fuel from each side of the carb flow if needed. Kind of like a small compromise of dual plane and single plane.

Just what I've read....
Click to expand...

Keep in mind that a dual plane doesn't feed one side of the engine separate from the other.
Each side of the carb feeds some cylinders on one side and some on the other.
This is why you would find statement like this about glowing header tubes.
"Strange thing was only 2 cylinders on each side were red. I am not sure on even side but I think 4 and 8 were red and 5 and 7 were red on odd side."
 
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They did some intake comparisons on Engine Masters and found the divider to cause problems on some intakes. Adding a small spacer helped in most cases, or mill down the divider a hair.
 
TrailBeast said:
Keep in mind that a dual plane doesn't feed one side of the engine separate from the other.
Each side of the carb feeds some cylinders on one side and some on the other.
This is why you would find statement like this about glowing header tubes.
"Strange thing was only 2 cylinders on each side were red. I am not sure on even side but I think 4 and 8 were red and 5 and 7 were red on odd side."
Click to expand...
Agreed and carb balance is very important with dual planes.
 
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