How to fix this intake?

I have tasked myself with making this MODMAN 'blower' intake better for a friend. It's going on a 485" CID "B" engine naturally asperated. I will be cracking out the bandsaw and welder and working within the confines of a flat hood. Along with wishing me luck, I'd like to see or hear anyone's results modifying this intake. I'd like to hear from anyone who's dynoed with this intake in stock or modified form. I wouldn't use this unless it were a 2x4 bbl, which it is. If I do get enough 'you're crazy' replies, I may revisit the project. But, I've played around a little with intakes. And this one, isn't the best IMO. pics...

Lengthening runners idea...

Probably should mention I'd like to limit final engine RPM around 7000. The first pic you might see the cardboard near the butterfly/barrel holes. The intended placement is to target a trajectory that splits the barrels. But the divider's end will fall short of that 'hotspot' in-length. If you have dynoed one, where did torq peak and in what application?

this is what i did on my 440 . Was just a quick made stuffer to reduce intake volume , removed about 20% . Might have helped to have used a "cross" shape and fill area between front and rear runners as well , like where you have carboard . Helped a bit but as i have said before , i feel these are more friendly with bigger cubes and or higher RPM . I was only shifting @ 6000 trapping @ 61/6200 . Felt great on street , ran similar or hair more MPH but was lazy sixty footbraking . I spent quite a few pulls on a chassis dyno with it . Tried different spacers etc .

Tex

just had a look in my dyno folder . Here's a couple of runs .
1 is modman no filler or spacer
2 is modman with filler with/without carb spacer .
The only time a really raced it was without filler if i remember correctly .
This might help Dizuster as well .

Tex

PS dont worry about HP curve , was always the same no matter what induction or ET car ran . It seemed to hit the converter stall speed and show no more

I am on my 4th version of insert in the intake. You just need to get the air in the ports and not floating around in the plenum.To me it wasnt all about quickest ET. It was getting the air/fuel to the ports the same each pass for NSS index racing.
The biggest gain was a plenum spacer. I found that a 1inch plenum spacer worked the best for my combo.
If it is a "max wedge port" opening done by Indy... there is plenty to gain by working that as well.
I know folks dont like the modman. It works for me.

Hey Tex, is that like 1 1/2 angle ? or solid ?
66coronet, can you post some pics ?
I have a max port RB dual carb version I plan to use on a 500 with 270s

B1Duster ,

that was i think 1 1/2" or 2" angle that i welded flat bar to and closed the ends , became a hollow triangular tube . As i noted i measured intake volume be fore and after . 5litres before pretty close to 4litres after .
It was a trial as there weren't many using that intake when i ran/did that . It was fairly new release when i bought it .

Tex

Any pics of the 'inserts'? What is the motor combination? I think you are a 540" cid and run 9.50 index? 3500lbs? You've gotta be over 800HP. A plenum spacer is in the works but I'm not sure yet how much additional height i have to work with just yet. The additional runner length it really 'needs' will pretty much mandate a spacer so as not to 'bias' distribution. That's THE FIRST THING I always try to optimize if i go into the plenum, power falls into place as a result. Also, as you said the runners need work on both ends regardless if i add to their length. And thank you!

Thank you Tex! It is for Diz. I'm not sure how to read these charts, it appears the intake with NO mods made the most power on your combo. Can you spell out the results in just text? i.e.- "The divider added 25ft lbs of torq across the board"

Those are awfully short runners for anything but a high RPM engine, IMO.

I would think anything you could do to let the engine see more runner length will
make an improvement, my 2 cents....

Joe

Am I missing something important?
The Modman looks very much like the original 1958 350" (and 383/343 hp) B 2 X 4 divided single plane iron manifold, or the Offy "360 degree", with the center divider removed.
I make some comparos on my site here: http://victorylibrary.com/mopar/intake-tech-c.htm

The closed off angle piece as both a volume reduction and a flow enhancement is brilliant! I have a feeling that the sharp top edge may "trip" mixture trying to swap left & right sides. Perhaps capping the angle with a half-round of 3/4" tube may help?

This is good stuff thanks. The center piece would be 'solid' or sealed in relation to the plenum I have not decided as to how the top would be shaped into the plenum. That 'problematic' area mostly serves as a runner extension along with the end walls needing some 'help' too in that regard.

Have you talked to Ken at Indy about that intake? I had a chat with him a while back and he said he had some tricks to make power with that intake. He probably has more dyno time with that intake than anyone else in the world so you might as well start there. It is a little easier to talk to Ken these days since Russ is out of the loop.

That thing in the floor needs to be sealed to the floor or solid to have any effect on the plenum volume, if it is hollow then the space under it will still fill and empty as pressure rises and decreases. I think it may change fuel flow through there or slightly change cross talk from cylinders on opposite sides of the engine but without being sealed it will do very little.

Also if the engine is going to be MPFI I would not lose any sleep over plenum volume but I would be trying to lengthen then runner length some. There is actually mathematical formulas to figure out ideal length and size rather than just adding some length and hoping it helps butt I hate math so someone else or a computer program would have to help.

I will have to look for pictures of the inserts.
The first one was a piece of aluminum angle. I showed it to an engine builder that used to work with some cup engines.
He talked me into trying shapes out of wood to see what the motor liked.Then changing them out for a metal version once you settled on one. He did tell me that it wouldnt be happy with the ridge or point.
Mine definitely liked a tent or teepee shape but the top does not need to be a point. Mine liked a flat or rounded top. I think the top of the point or teepee in mine now is about 3/4 wide with rounded edges.

My combo is a 540 wedge:
13 to 1 comp
roller 680 lift
Indy -1 345 cnc heads
modman with a pair of edelbrock carburetors.
4.10 gear
ATI converter
Its not a real aggressive combo.

Thanks for sharing.... I saw yours has been 9.49 best? What's it weigh? Mine is a pig (currently 3740 with the turbo motor this modman 485" will replace).

I FORGOT ABOUT THE WOOD TRICK! lol Thanks!

Just a clarification .
Poly , yes in hindsight i would do a semi circular insert . It would then be broader and may less affect air flow ? My thought was to split/direct air outwards towards ports rather than just smash the large flat floor area .
The insert was a fully sealed tube welded to intake floor . So equivilent to a solid bar .

B1 , here are the dyno sheets again , this time in color plus a chart to compare to single 4 barrel . Pull with no filler is pink , 2nd sheet pull with filler and spacer is pink no spacer is blue .
Pull with filler shows a TQ loss .
BUT i will say the dyno operator would often play with ramp speeds and this will affect readings . Did this affect TQ not sure . This was 10 years ago . Also they have very different correction factors listed .

Tex

Bill Jenkins used epoxy-coated wooden stuffer plates in the bottom of early SBC tunnel ram in 1970 to proportion plenum volume to engine size, he felt the stock manifold was too big for anything less than 380".
If the triangle is not completely sealed I doubt mixture would go through it, but it would still be a buffer volume damping vacuum.

The MM appears to make the plenum width almost match the flange pattern, but it doesn't need to for NA.
If the plenum box were taller, the sides could taper inward. Then make the box narrower and add the length to the runners. Something like this may be possible as surgery, but I'd rather try it on an old Offy than the $$$$ MM.

For blower use, of course the top comes off, but any Roots with helix rotors does not have uniform discharge along the length of the exhaust port. The highly developed Kobelco etc. port is a long triangle closely resembling a NACA duct.
Most of the volume enter the first 4 cylinders, and none at 7 & 8. A mask between the top and blower case can correct this at minimal cost.

It has been a good bit quicker since.
With all the ballast out it weighs 3495. I typically run it at 9.75 because its not as violent.

Not sure that you see this but, this is exactly what I knew but, I just wasn't going to call him to pick his brain and not make a purchase. Just the same if one of us makes a solid improvement, it just might benefit the company. Ken has always been helpful sharing what he knows. They could cast them with more runner but, then you'd still get someone cutting them out like you see frequently done on the single planes claiming that's the solution. Makes me wonder what Wilson didn't know when they modified your intakes lol.

Darin Morgan says the flat floors are best in an intake because of the pulsing between the cylinders. He said a vertical divider was the worst he ever tested. Wet flow is hard to predict from what I've read about it.

Worst for he was doing.
For Chrysler, it was the smallest, cheapest, lightest design to add a 2nd 4 bbl.

Horses for courses

Its a shame a dual carburetor under hood intake manifold is simply not made for the 340 360 mopar. Offenhauser still makes a unit but its design is for the 273 heads. It will bolt to 340 heads but its not ideal and its a design from the 1960s. Ford and Chevy have dual plane dual quad manifolds in traditional and airgap versions and from multiple manufactures. I like tunnel rams but I really like under hood dual quad setups. Harkens back to a time where to go faster- you absolutely had to add another carburetor!

The Mod Man is available for LA, Magnum, and W2 Mopar, along with a variety of tops.

Although, these days “available” is a relative term.

I had a customer try one on a 470.
He was running a 400-2, but wanted to play in the NSS stuff.
4 speed car, And he used Ede carbs.
I seem to think the big problem he had with it was a stumble right after the launch.
I don’t recall there being a big speed difference at the top end between the two.

a stumble right after the launch

That's what the divider cures, by reducing plenum volume by 50%.

Very much appreciated and thanks for sharing. I think the best cure would be a 'pump-shot' type of carb(S ). Whatever I do to the plenum I will take into account a compromise between ideal volume, packaging limits, and fuel distribution. It's unlikely the plenum will be significantly smaller than it is now in volume.

It's getting to be where the intake is about the last thing needing to be done, finally getting around to it.

I lowered the floor some. The plenum will have some awkwardly shaped wood in 4places to help lengthen the runners and 'bellmouth' the extensions. I'm not sure I'll be adding much of a center divider. I do not feel it needs ANY reduction in volume for any application, if anything that bridge down the center helps RUNNER LENGTH. If we could afford more delays I would split the top and locate the carbs more central to the ports. IN THIS PIC the runner roof was just roughed-in quickly AT THE PLENUM to see better the rest of the as-cast alignments.

General roughed runner extensions and their approx. placement.

"filler' idears...

I've been doing 'other things' so this went on a backburner but this is essentially what I'll try. There will be a TWO inch spacer above this and then one additional change was Scott buying the INDY "EFI" 2 AFB top which spreads the carbs apart a touch more so they are better over each runner. Talked with a few that run the modman and run well and there some basically unmodified in the plenum. That said, we could baseline it without the plenum mods..AH, NO!

Getting closer to epoxy...life happens in the meantime.

Hey hey...you're giving away our secrets! Lol

This spacer was not done by me. Credit goes to Scott's long-time friend Dave. He's good, I'm a hillbilly.

All the 'tricks' aren't disclosed, lol. Truth being I'd like to see Indy revise the lower casting because if this works you'd think it would sell at a premium price. Thought myself about making 'insert kits' a guy could rub and then epoxy together because...it's probably going to be better than a single 4 no-matter how bad I am.

I like it!
AFAIK the ideal shape for the divider nose isn't a knife blade (frequently seen), but a full radius, where the diameter = divider thickness.

All this work just to try and beat the old man.
Doug

Do you think the same idea/theories would work on a Six Pack Modman? I'm sure each engine is going to have it's own specific set of requirements, but was thinking about how to kill some of the plenum on a 500" street motor I'm putting together.

Correct and that law is obeyed as much as possible on this divider width...except on one area.

The cat is out of the bag and you may feel the target on your back! I feel IT IS a possibility!!!... when Scott buys a better/bigger block with added higher CR etc, AND upgrades to a better head/rocker gear so we can put a cam in it thereby using core pieces capable of another 100HP AND finds another 300 pounds of weight, IT WILL(might) BE a might be a close race! Wait ...prob get a converter too. LOL When are we doing a RB modman for the '64?

Prolly needs some 4150's too, we'll have to think some more but my head is already overcapacity.

SIXPACKDODGE..So if you look at the partial circles in blue on the center bridge, they are the trace of the 2x4 'carb' lid from Indy. In my latest pics, I better scribed (you may be able to see the marks?) the "NEW" 2x4 lid which is the 'efi' version which places the carbs more central to the ports allowing me to straighten the runners a fair amount. IN theory, this will help distribution and also performance. Ken L shared that idle distribution is BAD in stock form until you get up in speed at WOT. I'd assume the 6-pack is even more central in carb placement...

SIXPACKDODGE...So in the pic on post 3062430 it shows the runner extensions following the as-cast trajectory of the intake. That would be the difference in the way i added runner extensions for the 6-pack. i wouldn't add any bridge in the center and I'd ADD a spacer below the lid. ALSO, I'd use mechanical carbs with a pump shot. I think this is the way I'd do the lower with a single-4 "4500" with a lid like AndyF made...every version of this intake other than a blower needs runner extensions IMO.

Thanks for the response. A lot of good info. I agree on the runner extensions. The spacer, I hadn't even though of. Seems like in stock form, there'd be a massive bog until the r's picked up...definitely needs some velocity to make it work down low. I suppose the intake is a builder's piece, just needs tailored.

What HardcoreB and I found was that the runners are EXTREAMLY short for just about everything. We had the luxury of 8 runners and 8bbls, so he was able to point them pretty easy where we wanted them.

The spacer was for both plenum volume and giving the fuel/air some height to make the turn.

6bbl would probably benifit from the height, but aiming the runners would get complicated.

I hate to say anything good about Indy but I don't know what you mean by "fix" this intake. I bolted one on my friends 572 Hemi and couldn't believe how close it ran to the ported super duper $3,000 S/S manifold we took off.

Several years ago I reworked a set of std port Indy SR heads that went on a 493 with a Ede 6bbl manifold.
My recollection is it was a 10 second street/strip combo.
After about a year or so the owner wanted to try and step it up a bit, so he bolted on an untouched std port Mod Man 6bbl manifold.
Ran the same speed/ET.

That would have provided the option to open up both the heads and manifold to MW size.
I don’t know if that ever happened or not.

IMO the spacer is a very good idea, adding back some volume being lost with the changes. I dont think it is a bad a piece as the crossram deal personally, because of where it places the carbs..Just my

I respect and appreciate everyone's input and feedback! Your application is different being a Hemi and I haven't looked at or measured the runners to the valve. I'm not interested in testing the intake for this motor IN HIS CAR etc. After sorting the engine in the car the results will tell a story. Dynoing this against an unmodified modman and against a different good single 4 intake system would be interesting. I'd guess between the MW porting, adding the spacer and straightening the runner path on this application it's probably a good 100HP better. We feel it will be better EVERYWHERE, especially down low. The spacer will allow the fuel to distribute better among other more obvious benefits. Once it's done and bondo'd up it'll look 'better' from a functional standpoint. The dividers were tacked-in for long-term retention and the center bridge was welded along the sides but after blending is not air-tight to the runners. For now it'll use AFB's because that's what Scott wants. It'd definitely benefit from the tunablity (pump shot mainly) and increased flow of a pair of Holleys. Now if runs as well as we expect it to with the AFB's wouldn't that be win/win?

[u][/u]
I love spacers, I put that shxt on everything!

Is any of that part of the plan?

as a stupid person asking a stupid question, what kind of epoxy is best suited for intake modifications when gasoline with E10 or E15 is being used for street duty ?
TIA for those smarter than i will ever be.

Negative ghost writer. I feel the engine has proven to be good in a short period of time. In theory this intake should be better. I added 1 point of compression by swapping in flattops and retarded cam 2 deg @107.25 Based on the weights he’ll probably stop looking for mph around 800hp. Short of that, who’s to guess what a guy will do? All this stupidity started when we looked at the weight and thought “it’d be cool to run 10’0s” So, like anyone would else…I started going back into things

I had saved this blower/modman pic months ago

Sorry I missed this, all I can say is I've had good luck using "A+B" epoxy but that's been in race-gas engines.

thank you sir.

When I look at that gaping maw of a plenum with stubby little runners I see a chaotic hurricane of fuel mist getting slapped around by induction and reversion pulses. At low rpm the fuel is likely puddling on the floor. At the hit the end cylinders are getting a big gulp of dry air and the centers aren't doing much better.

That thing needs air flow. Big air flow. Bigger than that. A 440 will need scary rpm to make it work and will struggle getting up to speed. Big inch engines (bigger than my 541) would likely do better with it but, again, you'll have to work to get into the usable rpm.

Just my amateur eye speaking.

I do like some of those runner mods.

I know of at least two N/SS racers running a far less modified version of the Mod Man that have both been in the 9.50's. I constantly hear how bad the 440-25 Indy cross ram is as well. Both work way better than many give them credit for.
Doug

As long as it goes 10.0s I’ll be happy!

Not sure if you’ve read the entire thread but this isn’t exactly what the plenum will look like when done.

I read it and I'm interested in the results. In some situations it seems like I can see the air movement. This is one of those things and I'd like to know if my feeble imagination is on track.

i wonder if one were to bolt the intake to a flow bench, tape some yarn to the plenum, and watch what happens.
maybe blocking off the runners you don't want to see ?
or is that a common practice these days ?
i have no idea how anyone does this stuff these days, so just bear with an old guy's blabbering.............

Flow is going from the carb pad to the head back and forth at a unbelievable rate. The yarn would flutter.
Doug

Mine is modified. Sure, I wanted a quicker ET but that is not what started me down the path of modifying mine. I wanted to build a better mouse trap. The fuel stains from puddling told me, that I could build a more consistent combination. I spent three years in search of a way to make it better while slowing it down to run an index.When I ran restrictor plates, I found the car would pick up et at bizarre times. Definitely did not follow the log book and details.
Is mine quicker after the modifications? Yes. It wasn't the goal though.

pretty hard to do - its all about how they act under actual operating condition - with the different pulses created by the intake valves opening - Kaase has built some box type intakes out of clear lexan for this purpose
The mod-man intake was built as a universal design - its a clunky intake at best I have played with putting some brodix turtles in the base - seemed to help with bottom end on the street - I have not used one on a race motor

I guess I'lll see how this one works when it goes down the track in the spring. Lot of speculation until that happens.

HardcoreB followed some guidance on floor mods that others have tried successfully.

We also worked with Larry Meaux... and the runner length, plenum volume, taper, CSA, etc... is almost to a TEE what was recommended when he ran the pipemax calcs for me

Tried to make it is as well thought out as possible, it's certainly not just a shot in the dark..

It will be interesting to see how it works out - because much of your design could apply to the Indy Bathtub intake which is horrible for fuel puddling and turbulence - especially once you modify it and cut the runners back and put plates in like was done on Russ's intake

It will be interesting to see how it works out - because much of your design could apply to the Indy Bathtub intake which is horrible for fuel puddling and turbulence - especially once you modify it and cut the runners back and put plates in like was done on Russ's intake [/quote]
Yup those Indy intakes don't work. Especialty unmodified like this one.
Doug

Doug

Did I ever say they don't work ?????????

Yeah I hope I'm not portraying that anything is bad so much as what i think can be done to improve. AND AGAIN not that any of this makes sense but when did I ever do anything rational to a bracket/index car? (Although as Brett has said and Ken @ Indy has also mentioned, in as-cast form it has distribution issues.) But again I'm not willing to A-B-A to compare it to a stocker because it isnt mine and I'm sure it's better! lol The Universe has had other plans for me still but i did manage to mangle it more together and added a pic of basically the way it's planned to look AGAIN WITH SOME other things not shown. basically I'd go to press with epoxy in it as pic'd here. Doug has proven the Indy bathtub works in stock form no doubt. Many of us do feel it can be improved and not necessarily in the few different ways i have seen. I'll also say I feel confident a SM 2x4 intake on Doug's motor will make more power and go faster but, is that saying anything?

I would be curious to see how those spacers helped or hindered that manifold.

At least the outside might look decent?

Going to press with this...

that is quality work proudly displayed !