Single 4 Intake

[My427stang]

Frank, on big inch motors, I typically like a plenum divider notch. I do not make the divider go away, I think of it more as a damper.  Regardless, for yours I agree with Joe, that it could be a good idea to fill in, but not sure I would because I tend to be a bit more lazy and my alum spool gun still has a sloppy guy behind it...

However, I would listen to Joe and 427John, stick your finger everywhere and you should have no sharp or even 90 degree edges, even if those edges don't seem to be in the flow path  Specifically the roof of the plenum of the top plane and the transition of the bottom plane vertical wall into the runners.  Roll those nice and round, or at least get a good 45 on them, and if there is meat on the lower plane, raise that wall a little for a little more room to take the corner, but be careful and make sure you aren't trying to make a vacuum port

Think of those sharp edges in the plenum turns like water on a roof peak on a windy day, you don't want the a/f to separate and create droplets and a mess as it tries to take a corner, in addition to the turbulence it causes.

ON EDIT: With that last comment in mind, if you do keep the cut divider, blunt everything up, there is no place for a sharp edge anywhere IMHO, those jagged areas on what's left of your divider won't help you at all.  My experience says it will act like one of those people who spits while they talk LOL

[pbf777]

There seems to be plenty of meat on both the upper and lower runners, to do that, although getting to the back side of the lower runner, will be hard to do. I was hoping for a ball park radius to try to try to attain.

     Generally in an instance like this, as conservative in area presented by the plenum and as the ports are in dimension, the answer would to be as aggressive as possible with the casting material provided, but also maintaining and or bettering a balance in the access to the carburetor port to port.          

Should I make the rest of the divider, all one height?

     I would probably not recommend cutting the divider down, and would think that generally in this type of intake it would be better without the relief currently made; but testing is recommended at this point, as a simple piece of sheet metal could be fabricated to raise this notch recreating the 180° effect and simply added and subtracted for testing, as there are many reasons for the mixed experiences with this subject.         

     Also, if your handy at tig-welding aluminum, I have in the past filled in all of the waisted void in the carburetor pad deck surface and milling flat for a better relationship to whatever meets up to this surface.

     And don't hesitate to experiment with the addition of different carburetor spacer plates coupled to the associated carburetor tuning modifications that may be required in order to capitalize on any generated effect.         

     Scott.


     


     

[My427stang]

Making a divider could be an option, just go thick if you do, it's more violent there than you think.

If you could plunge a slot on each end, true the current diver and add a 1/16 or thicker plate, it could be removable and allow you to test, assuming you will dyno it

The other option is to fit a spacer with a tongue, slightly easier machine work

That being said, I'd still likely square off that current setup and blunt the edges, then let her rip

[frnkeore]

Thank you, all for helping out.

The the pictures I've outlined in red the areas that I want to work on.

For the divider, I'll weld in a piece of 1/8 aluminum, to raise it to the flange, my question on it, is will a 3 bbl, slot help, at all?

I have 2, 1" spacers to use. A open phenolic and a tapered 4 hole. If I use the open, I shouldn't need a 3 bbl slot. If I use just the tapered one, will a 3 bbl slot help balance the vacuum? Would using both be better, if I have enough hood clearance?

The areas that I outline in the runners are what I would like to know how large a radius would be the best shot. I have enough material to get a 3/8" radius, although on the lower runners, it will be hard to get a full 3/8 on the back side of it.

I'll get pictures of my spacers, before the day is over. It's raining like hell right now.

Scott, I can't fill all that with weld but, I will fill it with epoxy. Good idea.

[frnkeore]

These are the spacers I have, to use with this manifold. The numbers are the taper, top to bottom.

[My427stang]

On picture 2 and 3, don't just blend the corner where you drew red, round every sharp edge along the wall, it isn't a static flow to a port.  There is reversion from every port and pulsation from even the closing of the valve, like I said, if a sharp edge can be felt with a finger, blunt it, round it, blend it, whatever you want to call it. 

At worst belnding a corner with minimal flow doesn't help, but more than likely at some throttle position or rpm a sharp edge will wick some fuel and create turbulence at some other time

[pbf777]

     What's with the three barrel carb.?  I don't think this manifold would lend itself to this unit.         

     You only have one carb. spacer,..........the four hole, as the open isn't going to provide a good match-up (or sealing?) without the welding I mentioned and ported dual oval or double "D" shaped presentations at the carburetor pad to be proper.

     Yes, go ahead and fill the separation wall between left & right plenums, leave out the three-barrel notch, and it probably will respond well to having the carburetor moved up from the upper port runner set, so why  not use the four hole spacer.

     And again increase the radii as you have indicated as much as is reasonably possible with the material available, particularly the lower runner set, but be aware that the floor of the upper runner crossover is going to limit what can be done.  Ideally, the intention here would be to attempt to create the effect of drawing the lower runners upward shortening the distance to the carburetor, making it more equal to the upper runner set; and for the upper set since we're planning on the spacer, start the radius at the carburetor pad ending symmetrically at 90 degrees of the port runner roof; and port-match the outside perimeter of the spacer to match the intake presentation so that the spacer acts as a true extension of the intake manifold.         

     And, "epoxy" can prove questionable in the long term, but if it's the best we can do well................

     Scott.