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.