I think you are assuming that all eight cylinders have the intake valve open at the same time. If #1 cylinder is just opening the intake valve, and we have a 300 degree duration cam at .006" lift, then we have #2 still open (90 degrees past opening), #7 still opening (180 degrees), #5 closing at 270 degrees past opening, and #6 is already closed assuming the standard firing order. So only two cylinders are flowing a lot of air. I think Darin Morgan said we have about 2-1/2 cylinders open at any time. 936cfm (total)/2.5 cylinders=374cfm per cylinder.

Correct me if I'm thinking this the wrong way.

with that in mind, what about the long ram intakes with about a 3-4" [or larger] spacer ?
just thinking out loud here, as both a tunnel ram and a set of long rams with spacers would require hood modifications.

if the long rams ran out of steam at around 4500rpm or so, was that because of plenum volume being very small to allow for hood closure ?
what would a large spacer, open or 4 hole, do to these intakes, provided the spacer be sized for a much larger carb ?

I'm saving my lunch money for one of these ... Hemi blower manifold with Wilson fabricated top. Will run NA on my 604 and am boost ready for the ProCharger F-3R-130

The short answer is yes.....When I mill out the clover leaf in an Indy 4500 single plane intake and go quicker by .11, then I would say yes. Plenums for today's stroker motors is too small.

The plenum of the Indy 440-25 is quite large. Runners have good taper. Even with Eddy carbs its seems to work pretty well on my 572. We'll see how it works with some custom built 4150's this spring.
Doug

The RPM range stated with a manifold design is more about marketing than anything else. The average person isn't going to be able to select an intake manifold based on port cross section information etc, so this recommended RPM range is used instead.
A larger dual plane intake might fit the requirements you've discussed for a carburetted engine, but I doubt the ROI is there. Unless Trickflow decide the dual plane market is something they want to pursue.

As far as an intake for EFI, something like the manifold used on the Gen III Hemi, where the plenum sits under the long runners, might be the best compromise. Most of those wanting low RPM torque are probably not wanting to modify their factory hoods, so low profile would be something they'd want.

Just do this with 2 of Doms carbs. Only thing better would be blower or turbo. The fuel goes from the blades directly into the cylinder. No better design for n/a that i know of.

We I went to the 572", I went to the Indy 3x.

From what i found that's a duel plane intake. Duel planes are good for low to mid rpm performance. A tunnel ram is not going to work! Seems everybody is all over the place here. Sounds like that is what you are after low-mid rpm. With that said you need to match the other components accordingly. A duel quad tunnel ram is not going to perform well with a stump pulling cam. Unfortunately there is not a lot of aftermarket support stump pulling motors(low rpm performance). Until someone comes up with variable valve timing for big blocks it's a compromise where you want your power range.

No long rams for me just a good ol fashioned in line tunnel ram and enjoy the new found torque and hp.....

you want a intake of sufficient capacity to easily feed 500+ cubes . You dont always want a "race" motor . You would prefer under bonnet .
Why not look at the Modman ? Dual Eddy/Carter carbs , 6 pack and a large plenum . Will it make most power ? probably not . Will it feed the motor , yep . I never found it a problem on the street though it was soft leaving at the track . But i was only using a 440. Intake volume was right at about 5 L . Seems a few NSS guys are running them happily .

Tex

Forgive me if I'm wrong, but am I recalling correctly that you're going FI on this beast? Another thread on hemi bathtub and cross ram intakes made me wonder if modifying a wedge cross ram for port injection with a couple of throttle bodies up top wouldn't be a way to go. Maybe a bit on the spendy side, but it seems that drilling and tapping the intake manifold ports would be easy, and you can keep it all under the lid. If you had no compunctions about doing the same to a long-ram intake, would also be a potential avenue. (Or, am I going to be told to put down the whiskey and back slowly away...?)

Im no expert but my 5500 lb truck is not lacking much TQ down low with a 392 and 3.55s, it could use a little more but it is mostly due to CID witch you have covered, I would run something like a single plane trickflow with some port work, a dual plane is gonna give you more TQ down low and restrict it up high, with a TQ oriented manifold on a 500+ engine your gonna need a very tight converter to even be able to use that low end TQ. Theories are great and all but a lot of times they are not much ffun or just don't work in the real world.

I'm not a scientist, so take this with a grain of salt. But I think that using the 110 CFM in your formulas is messed up. Because of different vacuum levels. Heads and intake ports are generally tested at 28 in of water column. That is an equivalent of approximately 2 in of mercury. Atmospheric pressure is approximately 14 inches of mercury pressure trying to fill your cylinder. 14 in of mercury pressure is going to push a lot more air through your ports than 2 in of Mercury.

Be nice to see something like the pro-flow efi manifold in a max wedge port, or the weiand dual carb tunnel ram in max wedge.
I ended up with Indy dual plane with MW ports.

If you look at the SS/AH motors that require a "cross ram " intake almost all of them have very small offsets with more than likely runners that go straight to the intake valves, not like the Rat Roasters and NASCAR intakes with intake runners that are on the other side of the manifolds feeding across the motor to the intake valves

The offset is rule driven or they would be straight. At the RPM they run, no need for a long runner. Hence no crossed runners. Decent sized plenum especially with undersize carbs.
Doug

I agree. I brought that up because it's the simple math many people will refer to. I tried to temper that statement with the the other variables.

Hard to say what the actual flow is because conditions change and head flow is modified by the intake. Due to the different shapes and lengths of the runner path (throttle to valve) it's a bit of a crap shoot. I was thinking that most street oriented intakes are designed with stock-ish head flow values. Bigger engines really perk up with bigger heads. A little more intake might help.

I really like the idea of the Indy 2D intake but the casting quality really seems like second rate Chinese garbage. Drop good money on the intake and drop that much more getting someone to straighten it out and make it fit the heads.

I will try to run my EFI intake if I can fit it under the hood. The height is good but the throttle body neck might need to be reworked. It will require a different engine accessory arrangement due to the AC lines passing across the front of the engine.

It's an old Weiand tunnel ram with the top replaced by a 390 cubic inch plenum and a forward facing 1700 cfm throttle body. It's currently set up with 120 lb/hr injectors but that's a wee bit big for this engine.

i would think the real issue is building for 5300lbs and 3.23 gear. what are the goals? i don't think there is one correct answer for the question of manifolds.