I've been exercising the old noodle again and I've gone down the rabbit hole of intake design.

As big strokers become more commonplace are new intake designs needed? Not everyone is going for lunacy inducing power levels with big engines. Lots of us are using 500+ inch engines roles that are traditionally reserved for 383 and 440 engines. The biggest limitation on the RB engine is still the cylinder head so intake manifold design has been relatively stagnant. The bigger, higher flowing heads are finding their way out into the world so it stands to reason the intakes need to step up.

Street engines in the 530 inch and larger range are begging for heads like the TF270 but the only manifolds you'll find are for high RPM screamers.

Max Wedge port window aside, are the current crop of manifolds up to the task of feeding engines of this size? It seems that they need extensive (and expensive) port work to get the flow rates demanded by larger displacement. The Edelbrock Performer RPM is the go-to manifold for the street but at what point does it become a restriction?

The basic design of intakes does not change based on displacement but on intended rpm range. Compare a 440 and 541 in a street application. in low demand situations the RPM intake is going to be more than sufficient for either engine. It might be a little more responsive on the larger engine due to displacement generating higher port velocity. Under heavier loads at moderate rpm (pickup towing a race car uphill) the 541 is taking much larger pulls on that intake than the 440 is. Run it out to 6000 rpm and the Performer RPM feeds the 440 without issue but is it anywhere near capacity on the 541?

I think doing the simple math using displacement, efficiency, and rpm is a bit misleading. That says my 541 demands something in the neighborhood of 110 cfm per cylinder. I guarantee you a 110 cfm head would choke the life out of any RB engine.

Naturally, the cylinder head plays a huge role in all of this. Massive intakes do no good (and possible harm) if the head can't keep up. For all out race applications this isn't an issue since there are some tall intakes that will match nicely with the heads. It would be nice to find a more street friendly intake that could keep up with the 330+ cfm cylinder heads. The RPM can be massaged to get there but it's a little tall for those with hood clearance concerns.

It would be nice to have the time to develop a modern style EFI intake for these beasts but the market is too small for any kind of return on investment.

541" X 5,622 RPM at 100% VE is 110 CFM?
But that assumes continuous flow though each successive passage (booster venturi, manifold runner, intake port) which never happens. The port has a duty cycle (not on-off, but high-low) roughly related (but not linear) to the cam event. The CFM calculation assumes maximum vacuum @ WOT of 29.92" Hg.
The frequency of vacuum pulsing remains constant with RPM, but the amplitude (pressure cycling) is lower in the manifold, and even lower at the booster due to plenum volume.
Large displacement at moderate RPM makes it worse (as opposed to a smaller engine at higher RPM).
Where to go from here?
Obviously, a big plenum box extending sideways over the valve covers helps with the height problem.
Tuned length runners must be really long to work at moderate speed, and not really needed with big inches, and any port extension inside the manifold deducts volume from the plenum.
Anyone got ideas?

Thats why most newer stuff has variable runner length. My street car Hilborn EFI loves 24" total runner from back of the valve to the opening of runner, its all about the speed of sound & runner length, timing the pulses to take advantage of the ramming affect

This is a really good post. Some thing like the Offenhauser Small Block Chevy Ram Intake Manifold.

Are you running stock heads? If not what kind? Indy has both heads and intakes but you didn't say where your power range is. Is it a drag car or trailer puller? There where differences depending on witch Edelebrock(single plane) you got for a 440. I don't think they even make them anymore but the TM-7 was a way better intake than the torker was. I also have an old Weiand with even better runners than the TM-7. If i was building 500+CI Iwould probably run indy heads and intake. You might want check this out.link

I used 93% efficiency to suggest a typical moderate build. At 100% it slides up to 116 cfm per runner. As a whole, the math says 936 cfm for a 541 at 100%. Then, you get into real world restrictions, carb sizing bumps, and such.

Breaking it down into a single cylinder is a bit easier because heads are rated per runner, not as an engine set.

It would be nice to have a variable runner EFI intake but that's a completely different can of worms. While I might like it very few would want to put "that ugly thing" on their engines and Mopar guys are notoriously cheap.

I would think that frequency of vacuum pulsing would remain proportional to RPM instead of being a constant value. Amplitude would certainly be lower at higher rpm due to changes in density.

Plenum volume is a bit of a mess on a carbed engine since fuel puddling can occur at low air speeds. Having a wide carbed plenum can also play havoc on fueling since liquid (no matter how small the droplet) has far more density, and therefore inertia, than air. Fuel can fall down go boom at low air speeds and get splattered against a wall at high air speeds.

Throttle body injected engines need a bit of open plenum below the injectors. Divided dual plane intakes often struggle with those systems.

Port injected engines are more tolerant of plenum changes because the flow is dry.

The test in that link is for an engine running significantly more cam than I am. That skews the results since the cam will still dictate the operating rpm. Overlap is overlap no matter how many inches you have.

I've got Edelbrock Performer RPM heads being ported as we speak.

This thread was referring to larger engines in street and mixed use applications. Full power builds already have dedicated manifolds.

In my situation, I plan on cruising and misbehaving with a 5300 lb car wearing 28" tires and 3.23 gears. As for the engine, Take a look at this dyno graph for a modern hemi.



Now, draw the same shape curve but make every point 200 lb/ft higher. Do the same with the hp but lift it 175.

That is what I want.

Good street manners, able to run power brakes, and behaves like a stock engine but able to go on a rampage at the drop of a hat. Think of it as Godzilla putting on a top hat and black tie before he trashes Tokyo. Clark Kent and Superman. I did it last time using turbochargers. This time I want to do it with displacement.

What about a dual quad intake with either dual TBI units or dual throttle bodies with port injection? Would that help driveability on the large CID engine in a lower RPM case like your will be?
RT

Andyf tried that a while back. He picked up about 20 hp and 20 lb/ft by switching to the Mopar clone of the Performer RPM. He was using a Comp roller with about 6 degrees more duration but similar lift to what I've got.

Only read posts you agree with

Well just to give you a run down for reference of what we have>

589ci street wedge motor, 10:1CR
572-13 CNC365 Indy heads
s/roller 260/270@.050, .625"/.625"
440-2 Indy intake, old 950HP carb, 1.375vx1.750 base plate
2.18">2.14" TTI step hdrs
max dyno power was from 5500>5900@695hp at 33 deg. total.
max torque of 720ftlbs@4400

At 6000rpm motor pulled 2.0hg vac on dyno
through the traps@6200-ish rpm its pulling approx 970cfm based on 1.5hg std.

I think for a street motor with your intended use, you have 4 intakes to choose from. The RPM, the Six Pack, 440-2D and Holley SD. The RPM and 6 pack will gas-out first, but can get you to 550 HP. Even on a 500 inch motor, 440-2D dual plane makes better low and midrange power over the Holley SD, but will make about the same up top too. They will support 600 HP.

I would have expected a bit larger carb. Have you tried anything larger? The vacuum is pretty low but you never know.
What elevation is the track you frequent?

If I had purchased the proper pistons I would have bought the TF270 heads and the Indy intake. It surely would have perked things up a bit.

Mine are Eddy std port heads. The 440-2D is standard port.

This is our track>
https://airdensityonline.com/track-results/Santa_Pod_Raceway/

Best track in the UK arguably Europe. A 1050 Dominator was tried on dyno day and made only 3hp more, (pulled 0.7hg@6000) perhaps carb was junk,or lean, I doubt they messed with it too much to get any better gains. Talked to Dwayne about a bigger carb as well as Mark Whitner and they both said there may only be a 1/10th in the 1/4 with a Dominator with the combo we have, Our 10" proX converter is only 3600-4200 stall was main reason along with CR/low lift etc., its a mismatch of parts really but it does what we want and it runs good through full exhausts and makes almost the dyno hp on track. A 440-3 intake, 1050 Dom, 12.5:1 and 750" lift to use the heads better and then it would work no doubt and we'd be closer to 800hp than 700.

I have all of these 4 intakes in my garage but haven't decided which one to use on my 500" build. I'd like to put the Indy 440-2d on the engine first but unfortunately it has some core shift (center ports are moved up on one bank and lower on the opposite side). Once I have the engine fully assembled (with heads) I can see how much rework is needed.

Tunnel ram is the answer here.....

Put a real carb on that thing.....

I figure a 500 inch street motor could do well with a small plenum single plane like a Torker or M1- maybe a Team G. The extra cubes may bring the operating range down. In the case of the Torker the range on a 440 is 2500-6500 RPM. On a 500 plus displacement that range may shift down to maybe 2200- 6200 RPM?

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.

It might be difficult to believe but there's more to life than drag racing. This is a plus-sized cruiser that is the perfect candidate for silly amounts of torque. Think of the Mercedes S65 AMG. A 5.5 liter twin turbo V12 cranking out 635 hp and 720 lb/ft in a 5300 lb sedan. Why? Because they can.

I'm building it because it's my car, my engine, and I want to do it.

The car is so big it's a bit absurd. You just can't take it seriously. However, it cruises down the highway like nothing else. I like having a little fun with my stuff and being just a wee bit different in my builds.


Anyone can build a cookie cutter car by following the same old thing everyone else has done. That's boring.

i'm the kind of person that "if i can't drive it, i don't want it". driving it can mean compromises in performance sometimes and i've always been ok with that. i use a ch28 for my torquey cruiser and really like it.

And when you blow by some ricers/late stang-camaro-chally gents, racing on the freeway, with 6 or more friends in the yacht its all the more satisfying.

Feets, I'm toasting your attitude and your inevitable success !

so i had a indy tunnel ram on my 605 cuin hemi for 3 years i had 2 1050 dominators on it tryed all kind of jetting and timing and air bleeds,,, then i got a raybarton 4500 single dominator intake and a 1250 carb and it picked up 3 tenths and 3.5 mph over the tunnel ram on the 1st pass !!!! [censored] thats my kind of luck though

How about the mod man intake, You can run a single 4BBL, 6 pack or duel quads depending on what top you use.

And for a short time I'll be in front of them and behind them at the same time.

Modman is quite adaptable but extremely expensive. Those short runners are not likely to be of much benefit to a moderate RPM engine like most people use on the street.

. .

Maybe with the new ownership the 2D won't be the exercise in core shift I've heard they are. That would be the intake I'd run, A scaled up stock type one.

and, too much plenum volume. might make a good blower manifold.

Anyone remember these??

https://bangshift.com/bangshiftapex/mcfarland-torklink-intake-manifold-is-a-neat-twist/

The complex interior design and advantages are clearly visible.
Or, it's a shoe box...

It looks like a shoebox got dropped in a vat of molten aluminum,
BUT
I'm most likely going to run the ModMan
BECAUSE
By my own mandate, my 541 MUST HAVE A 6BBL.
So, I am fortunate to have bought a beautiful example of the Weiand P3690982 6bbl intake, the "old school" Super Stock intake that far too much research for any sane person has informed me makes the most power when a 6bbl is the choice of carbureation, other than a custom intake.
BUT
I also can't bring myself to run TF 240s on a 541 Bill Mitchell aluminum RB block
So, that means Max Wedge port size and TF 270s. The Weiand can probably have material added to the cylinder head end of the runners and then hogged out to MW ports, but I don't think that the runners have enough meat to open them up to the plenum floor
AND
I am hooked on the look of my N96 Air Grabber hood on my 70 V-code Roadrunner
So, that leaves me needing a 3x2bbl intake that will do some degree of justice for my 541 cu in Bill Mitchell aluminum block based stroker motor in my 5 speed, 4:10 geared mostly street driven Roadrunner.
That leaves me with the ModMan. Indy still will CNC the ports to MW size for $100
If I switch over from my Promax modded Holley carbs to a 3x2 F&B DPI/EFI I'm sure the ModMan would work even better, but I have to start with the Holley carbs.
If by some tragedy the ModMan doesn't fit with the Air Grabber, then I'm left with the factory aluminum dual plane 6bbl intake, or give up my beautiful hood, go to a "tall" 6 pack scoop, and that would make me consider a custom top for a 6bbl 440-25 setup or see what can be done with the Weiand as far as porting.
I have the Innovate Motorsports DLG-1 dual wideband O2 sensor system.