Yes top and bottom are flat with a taper to the outside cylinders. Next time I am over at Dad's I am sure he will let me measure the runners for you.

This will give you an idea on taper. Even though it is a 4cyl it has a nice shape. Also notice the nice bend at the inlet.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

As Greg pointed out, this is not the case in a dry manifold. The injectors are now what delivers fuel to each of the cylinder and they are equally positioned well inside the runners at an equidistance from the valves, so the plenum is basically just a big aluminum breather that you bolt the TB to, and each runner is like a straw in a big punch bowl and will only draw in how much air each cylinder needs.

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There's no such thing as too much cam....only not enough engine!

Ed, thanks for the explanation of how the triple weber carb setup works.

Tom, I really am impressed with your dad's manifold!

Brian

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Flyin' Brian

74 Duster, 225, rear-mounted blow through turbo at 12psi boost, street/strip car
"Sixy Beast"

Can't wait to see the prototypes!

I assume you will be using a Mustang TB flange?

I haven't really patterned the TB after any specific one yet, so it can be made to fit most anything at this point. I have seen many generic ones on eBay, but didn't know if any of you guys had a preference as to what type or brand you might like to use.

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There's no such thing as too much cam....only not enough engine!

nice work here,, but for runner length,, have you considered making a two piece manifold,, mounted to the cylinder head would be one section, with the injector nozzels and with cast connector couplings,, the air box would be a free standing unit with matching couplings,, the purchaser would then insert lengths of silicone hose sections,, one could custom tune the length to about anything.
the coupling connectors would need good roundness and surface finish to prevent leaks.

there would need to be bosses on the plemum for mounting brackets...

may actually simplify the casting / cores...

I don't know if the silicon tubes would be up to the task of supporting the weight of the plenum plus the TB, then you might have rigidity issues with the throttle linkage trying to open the butterfly with only the boots supporting the assembly. I think one single part reduces it to the simplest form for both machining and casting. I believe several people have tried both the Offy and Clifford intake with TB and injectors with pretty good results, their runner lengths are probably suited well for most anything from stock to 300 HP maybe. Any thoughts on that?

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There's no such thing as too much cam....only not enough engine!

I can not find the article anymore but they actually made it adjustable by using air horns inside the plenum. The top of the plenum was removable and you could mount different length air horns on the inside.

The air horns also helped with air flow into the runners.

Very similar to this but it was for an inline 6.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Something like that could work, I remember back in the 5.0 heydays a company made an intake similar for the 302 that had interchangeable length runners inside a removable top plenum like that. Is this something like you were describing DadTruck

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There's no such thing as too much cam....only not enough engine!

getting the air intake divorced from the surrounding walls as shown in the tom drake photo really helps to reduce wall friction and improve air flow, the provision for adjustable runners is another kick that would let tuners have their way. That does add mfg cost, maybe should be considered as an option,, but one that ai would want.

The best advice is to develop a product that gets the buyer a competative advantage,,(cost vs performance),, (interchangeable length) if it works,, folks will be beating down your doors to get one. Indy Cylinder head has a multi top plate manifold, accepts a single 4 bbl, two 4bbs,,,, make some thing folks can tune to,, that way from a product stand point, if it does not work, it is the tune,,not the product that does not work,,, and if some one can figure a cam and runner length that runs really well,, every one wins.

There is an article somewhere on the net, where one of the Mopar engineers who designed the Hyperpak manifold, described the method they used to get the runner length correct. Unfortunately my PC's hard drive with 20 years of Mopar notes crashed, so I have no urls to that article.
Anyway, they used the sound frequencies made by rushing air in the intake runners at different rpm levels to find the optimal length, if I remember correct it was 13 inches long runners that delivered the most even power through the entire rpm scale. Take into consideration that this was for a carburetted intake manifold, so plenum volume and runner layout could influence the design, but it shouldn't be much off in any case.
BTW, the way some EFI manifolds look, you shouldn't believe that they work at all! I don't think you have to be very concerned about where the throttle body is placed, air moves from a low pressure zone to a higher pressure zone in a blink of a second anyway.
Nice work!

Olaf

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Aspenized

This looks more like what DT was describing above.

This is an idea for better airflow into the runner without having a complete air horn inside the plenum.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Thanks Dad and Tom, the more I think about the adjustability of the different length velocity stacks inside the plenum for tuning, the more I think that even though more cost will be added to the product, the unlimited value the customer will be receiving for that added cost will be much greater. That way like you said, if it doesn't work its the tuner, not the intake.

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There's no such thing as too much cam....only not enough engine!

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

In most cases, a radiused inlet on a flat panel - like the one Tom Drake posted - flows better than an inlet pipe, or even a tapered air horn, in a plenum. I suspect the plenums with internal horns are used for hood clearance.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair