Intake design

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Sky65

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Aug 27, 2008
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What was the advantage of the stock gm aluminum intake design with the three hole plenum? No one uses it anymore. Is the two hole better?

Winters 441 intake, 65/66 350/365 hp engine.

2aez776.jpg

Edelbrock Performer RPM. Other manufacturers the same design.

7101.jpg
 
I think the point is to reduce the plenum volume on 1 side. If you look at your dual plane intake, the one side is really really really deep.
 
I'm not sure I understand that. Why bother to make two plenum sizes if you are going to reduce the size of the larger one anyway? I thought perhaps it was to increase the vacuum signal on the deep plenum side. It almost looks like having a four hole spacer, just a two hole, on the deep plenum side. I don't know. It is confusing to me.
 
The way I look at it is they were trying to keep the lower runner/plenum the same volume/flow as the upper combo.....

....anyone???:bonkers::search:
 
I though I had one of those high rise GM intake,it's from a car I had in another life LOL. A Nova SS 73 for a while it had a 302 from a 69 Camaro angle plugs and stuff. When I blew it I replaced it with a 350 LT1 from another Camaro I still have that intake and the Holley in a box.
I just checked and its a replacement for a 70 camaro or Vette 350 LT1
Casting says 3972116 it has 2 holes not 3.

Is Grumpy around??? maybe he'd know.
 
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Sky65 said:
I'm not sure I understand that. Why bother to make two plenum sizes if you are going to reduce the size of the larger one anyway? I thought perhaps it was to increase the vacuum signal on the deep plenum side. It almost looks like having a four hole spacer, just a two hole, on the deep plenum side. I don't know. It is confusing to me.
Click to expand...


The one with the 2 holes is the deeper of the 2 plenums. It's twice as deep (roughly) as the other one because it's the bottom set of the dual plane. This is to increase or at least even out the vacuum signal with the other side.
 
Twin_Turbo said:
Sky65 said:
I'm not sure I understand that. Why bother to make two plenum sizes if you are going to reduce the size of the larger one anyway? I thought perhaps it was to increase the vacuum signal on the deep plenum side. It almost looks like having a four hole spacer, just a two hole, on the deep plenum side. I don't know. It is confusing to me.
Click to expand...


The one with the 2 holes is the deeper of the 2 plenums. It's twice as deep (roughly) as the other one because it's the bottom set of the dual plane. This is to increase or at least even out the vacuum signal with the other side.
Click to expand...
What does "even out the vacuum signal" do? Does it help the bottom end or midrange? Improve throttle response? I am asking because I have an old 441 intake and I wondered if it would be better than an Edelbrock or a Weiand. But then I wondered why nobody makes intakes that way anymore. The two hole design maybe is better? Do you know the benefits of each on the same engine?
Thanks
 
Even booster signals mean that you will have a more uniform mixture distribution between the 2 planes. One side feeds the upper and the other side the lower plane. Differences from cyl. to cyl. will still exist because of runner length and shape.

It must have been a dud, I don't think there is any current manifold that still has it. Another idea is the cut down center divider. You see that on some manifolds still. The 2 carb sides are not separated entirely.
 
Twin_Turbo said:
Even booster signals mean that you will have a more uniform mixture distribution between the 2 planes. One side feeds the upper and the other side the lower plane. Differences from cyl. to cyl. will still exist because of runner length and shape.

It must have been a dud, I don't think there is any current manifold that still has it. Another idea is the cut down center divider. You see that on some manifolds still. The 2 carb sides are not separated entirely.
Click to expand...
Cool. Thanks!
 
Twin_Turbo said:
Even booster signals mean that you will have a more uniform mixture distribution between the 2 planes. One side feeds the upper and the other side the lower plane. Differences from cyl. to cyl. will still exist because of runner length and shape.

It must have been a dud, I don't think there is any current manifold that still has it. Another idea is the cut down center divider. You see that on some manifolds still. The 2 carb sides are not separated entirely.
Click to expand...
Probably more difficult to cast.
 
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