L78 intake plenum divider - Page 3 - Chevelle Tech
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post #31 of 43 (permalink) Old Dec 23rd, 18, 9:33 AM
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Re: L78 intake plenum divider

At the least, it will help balance the flow between the primaries and secondaries.

IT in no real way adds to this thread, but when I slipped a Wieand plenum divider into a hogged out 163, the car felt better all around - street driving wise anyway. I attribute that to a big 850 cfm sitting atop an undergeared, aka torque starved 427.
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post #32 of 43 (permalink) Old Dec 25th, 18, 9:05 PM
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Re: L78 intake plenum divider

Think it all depends on the car, gearing, combo etc.
I notched a 300-36 Holley and lost some signal to the carb, no increased top end.
To make a blanket statement saying do it or not because some article, or dyno sheet says so imo is inaccuarate.
What works for one guy may not work for the next.

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post #33 of 43 (permalink) Old Mar 30th, 19, 2:02 PM Thread Starter
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No leaks and Intake seems to be a good upgrade from the Performer 2.0.
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post #34 of 43 (permalink) Old Mar 30th, 19, 2:38 PM
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Re: L78 intake plenum divider

I opened up my plenum a bit. Will see if it makes any difference in a couple months. Cut and thinned the divider, and a little radiusing around the edges.



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post #35 of 43 (permalink) Old Mar 30th, 19, 8:12 PM
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Re: L78 intake plenum divider

Can someone elaborate as to why you wouldnt just remove the whole middle section?

Why leave some?

I have a weiand intake that I am now going to pull out and grind away...just dont want to take too much.


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post #36 of 43 (permalink) Old Mar 31st, 19, 9:48 PM
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Re: L78 intake plenum divider

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It's a street car, but will go to the track some. I'd love to see some 12's.
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I opened up my plenum a bit. Will see if it makes any difference in a couple months. Cut and thinned the divider, and a little radiusing around the edges.


I have that same intake!!!
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post #37 of 43 (permalink) Old Apr 1st, 19, 12:44 AM
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Re: L78 intake plenum divider

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Originally Posted by fishhead View Post
Can someone elaborate as to why you wouldnt just remove the whole middle section?

Why leave some?

I have a weiand intake that I am now going to pull out and grind away...just dont want to take too much.
I'm going to assume intake manufacturers know more than me, and there may be a reason why modern intakes have the gap cut down only by about an inch or so. I've cut mine down about 1.5". Perhaps I could have gone down another 0.5-1", but I do run a 1" open spacer as well.

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post #38 of 43 (permalink) Old Apr 1st, 19, 8:52 AM
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Re: L78 intake plenum divider

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Originally Posted by -SS454- View Post
I'm going to assume intake manufacturers know more than me, and there may be a reason why modern intakes have the gap cut down only by about an inch or so. I've cut mine down about 1.5". Perhaps I could have gone down another 0.5-1", but I do run a 1" open spacer as well.
I understand and agree...however, look at a torker intake. It's all open. Just a big open space and then the runner. What happens to a dual plane like our weiand if we open it up all the way?

The other thing I thought...with that divider in there, you add a riser, the flapper wont hit the intake, but that divider does sort of separate the left and right banks of the carb.

Opening that up allows all the a/f mix to go where it needs at that given second. With it closed it seems very limited. So what are the negatives to opening it all the way vs partially?

It's really important to me as I want to use a holley 3 barrel carb on my 454 for nostalgia sake and I dont want to do something that will make the 3 barrel become too big at 950 c.f.m.


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post #39 of 43 (permalink) Old Apr 1st, 19, 2:11 PM
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Re: L78 intake plenum divider

I race with a fellow with a stock appearing L89 Nova that runs [email protected] MPH on bias tires with a 163 intake with the divider removed.

Pay attention to the ALL of the details of proven combos that actually run at the track and you can never go wrong.
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post #40 of 43 (permalink) Old Apr 1st, 19, 5:58 PM
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Re: L78 intake plenum divider

Quote:
Originally Posted by fishhead View Post
Can someone elaborate as to why you wouldnt just remove the whole middle section?



Why leave some?



I have a weiand intake that I am now going to pull out and grind away...just dont want to take too much.
The theory says that the intake charge on the taller floor side at high velocities will "spill over" and keep going to the bottom floor since it has inertia and not go to the side it is intended for. A small dam keeps most of that from happening

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post #41 of 43 (permalink) Old Apr 1st, 19, 11:47 PM
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Re: L78 intake plenum divider

The last cast iron intake I ground on to remove the divider i used my AC225 welder cranked up and a 6011 welding rod was used to gouge the divider and guts out of the plenum.. then finish the last bit of work with a die grinder.

That sure made the job at hand go very quick.
That is for us guys that do not have a mill.
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post #42 of 43 (permalink) Old Apr 2nd, 19, 12:03 AM
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Re: L78 intake plenum divider

I'm now considering cutting my divider down even more. Turns out I only took about 1" out of it, so maybe another 0.5" would benefit.

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post #43 of 43 (permalink) Old Apr 3rd, 19, 2:57 PM
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Re: L78 intake plenum divider

Testing! Testing!

Another comment, while its not going to a full open plenum, it does somewhat INCREASE the signal to the carb, as now it no longer only sees the 180 its connect to, but 360 due to the cut out. Same reason a rejet is oft required when switching from single to dual plane.

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