applying intake design

[Dannyho]

I'm goign to be building a custom intake for my old musclecar, and of course, I want it all. I can accept this is not possible, and I'd like to try and work from an existing design that looks like something I can duplicate at home, but still is an attention grabber when the hood is open. Such is how I came up with the Ferrari 360 Modena engine. It basically is a 2 throttle body setup, but if you could imagine an engine with velocity stacks, with each cylinder banks' stacks enclosed in its own little bubble, and a crossover tube connecting the two bubbles. How do I calculate anything for this setup. I'm familiar with hemholtz theory and I have all the equations, but even then I still bought and am reading "Scientific Design of exhaust and intake systems" as recommended somewhere on this board. any ideas on where I can jump off, I've linked to some pictures so that someone could see what I mean. should I work it out as a velocity stack setup and call it a day or what?

 

[patprimmer]

They used to be called cross ram manifolds.

They mount 2 x 4 barrel carbies, one over each cylinder head.

The top plate normally is removable.

If you can get one, you would just need to make a fancy top cover with some throttle bodies. Lots of small throttle bodies might look fancy. One big one either side will probably be most practical.

If you want to go cheap and easy, you can use old carbies, bolted to the original top plate, and with the venturis bored out to throttle plate size as the throttle bodies.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Fabrico]

Good news! They are still called Crossram manifolds. There are a couple of companies, like Offenhouser, making them. (On ebay too) You could grind/blast the makers name off or cast up a new top cover with your name.

 

[Dannyho]

well I'm definately going to go with EFI and two throttle bodies, but more along the lines of the geometry laid out like ferrari has it. those cross rams have the runner molded into the "plenum", something I'm not going to be able to recreate. on top of the fact that those cross ram manifolds can be hella lot of money, but more than that they don't make them for my engine, a 318 ci chrysler small block. assuming that i'm wrong and someone does make them, I'd like to have the intakes in the front of the engine rather than top, for clearance reasons involving tubing and air filters.

But is it as simple as designing for velocity stacks and individual TBs and then enclosing them or is there something much more complicated?

I also couldnt find any cross ram specific information on design and application

 

[MikeHalloran]

Looking at the right side of the photo provided by Fabrico, you can see the end of a velocity stack through the carburetor opening.

Compare with:

http://victorylibrary.com/mopar/intake-tech-c.htm

especially with the
Chrysler 413 300F factory and
326 Race Hemi Edelbrock Rat Roaster 2
photos

One big problem you face is fitting the EFI injectors to such a setup. The injectors and fuel rails almost have to be contained within the plenum. I suspect that the Ferrari's intake ports come straight up out of the heads, so the injectors can be fitted to the outboard side of each runner; not really an option for a 318.

You might fabricate a multi-piece manifold like recent Fords use. A lower manifold carrying the injectors, terminating in a horizontal plane with 8 holes for the runners, with the remainder of the runners in a secondary casting bolted atop the first. The runners could be set as cross-rams, or folded back over the rocker covers, or whatever you like. One disadvantage of this construction is that the assembled manifolds tend to be rather tall.

A manifold similar to the one Fabrico shows was fitted to the penultimate generation of Camaros, equipped with dual TBI throttle bodies. They did not exactly set the world on fire, for a lot of reasons other than the manifolds, but TBI makes injector installation less of a problem.

You might be able to fit normal EFI to an extreme long- tube cross- ram as shown for the 413. It would look pretty cool. Hydraulic lifters would be a wise choice...








Mike Halloran
Pembroke Pines, FL, USA

 

[Dannyho]

that's a really great link, sorry the pictures are so small, but you see, on the modena engine and the way the cross rams intake runners differ. the cross ram actually has a smooth transition from the lip of the runner to the wall of the plenum (albeit only on the bottom of the runner), whereas the modena engine has the entire circumference of the runner come through the bottom of each plenum and sit above the plenum bottom.
I have some very good cad programs at my disposal and i can be creative when i have to, packaging will come later, once i can have every part mocked up, right now i have to deal with figuring out what direction i want to go in.
I just really want to know if my assuming that to determine the size and length of the runners on an engine like the modena's as described, if i would do it the same as a tpi manifold.

 

[Fabrico]

An example of a long runner EFI design is the Mercruiser Crossram MEFI system for BBC's. Very wide powerband with a flat, reversable plenum. It uses a sideways mounted 1000 CFM, progressive opening, 2 hole T/B.