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?