Youre right, datto12qld, nothing beats hands on, and things like the compressed air method to test it is might seem simple to some, yet ingenious to others!...and if you do end up with that manifold sitting around, I would be more than happy to take it off your hands :)
CAD is still good for visualising (dreaming) even without the means to replicate it.
This is what I came up with with my limited CAD skills, yeh its maybe a lil too kinky for the 2 and 3, maybe a bit outta proportion in length for the 1 and 4, but ys think something like this would work?

Dunde1000s Manifold is the best Ive seen in a while



It will suit twin 2 inch SUS the biggest Muthas round or even custom 2.5 inchers :)



Wont need the overkill twin fuel bowls for an A series though. Even halve of one would be fine.

Heres a bit of inspiration for ya:
http://www.youtube.com/watch?v=DUVQyPMrpq8
http://www.youtube.com/watch?v=_MFbN0tJ5fY

To be honest I dont think it matters too too much, sure for absolute peak horsepower blah blah yes it would help.
but really if you want all out peak horsepower why have you got a datto? :D

I think the best bet is to position the carb in a practical location, bolt the carb plate onto the carb, bolt the manifold plates onto the head, then join the dots. Keep in mind the air/fuel will 'slow down' around corners so less bends is better.

I basically tacked it together then got the air compressor and blew air into each runner and tried to get a 'feel' for how it was flowing, moved bends here n there until the air coming out the port holes felt about equal... not very precise i know but it does give you an understanding of whats going on in there as you change it.

Start by making the port divider, make them as symetrical as possible and tack them on first, all the rest can be moved easily.

Best thing about using mild steel is it is easy to weld, cheap to modify, 'softer' to work with then stainless etc
Just play around with it and see what works best.

When your happy with it, make it out of stainless or alloy.

If you decide to go with a stainless final version, you can tack it all together using mild steel wire (or gasless), just put as few tacks on as needed and try to put them in easy to get to places, that way when you take it in to a welder/ fabricator all they have to do is put their own stainless tacks on then grind yours out and weld.

can save you a lot of $ on labour etc not to mention practicality.

Obviously this rapid prototype method doesnt suit everyone, but not everyone has a TIG and milling machine in their shed.

There is a bloke coming to look at my A15 motor this weekend, if he doesnt want the manifold you can have it to play with or dissect etc, as I have no use for it any more (sold the carbies)

yessum, done a bit of floworks.. Solidworks is really awesome..

I know! coincidence?...actually it is.

Dundee, Ive been goofing around in Rhino for the last couple of hours with those flanges, decided to do a youtube crawl on CAD manifolds...
Did you know solidworks could do THIS???? I kinda gave up after that, kinda overwhelming...

wow, and who just got a gasless mig ey wurzel

Ah you make it sound so easy, great work and thanks for the info!
So its important to have the runners the same length?...some of these lynx crossover ones seem to be all over the place, IE: the 1 and 4 runners heaps longer than the 2 and 3.

Hey mate, you could always knock something up yourself.

I made a single sidedraught manifold for my A15 using only a drill, grinder, die grinder and gasless mig wire.
Although i made mine out of mild steel (only a test after all) you can do all this with stainless if you plan on keeping it.

I got 10mm thick mild steel manifold plates waterjet cut, cost $60 (take in your standard manifold for them to trace)

I used alumanized mild steel (exhaust pipe steel) 1.3/4" / 38.1mm.
From memory I simply squeezed the pipe in a vice and it lined up EXACTLY with my ports although mine were slightly larger then stock oval port, you are handy with a dremel so just grind the 10mm plate so theres a smooth graduation to the head.

for the bends buy a couple of 180 degree mandrel bends from an exhaust shop.

You may find you will need to rotate the carb toward the front of the engine bay for clearance, (i had a dellorto 45 with intake trumpets in a 1200 ute and there was no room)

as you can see in the pics i roughly equalised the flow by making the shorter path having more curves and the longer path straighter, the seat of pants dyno said it was pretty close anyhow.

To add a vac hose nipple (for the dizzy) i just cut off some old brake line, drilled the same size hole into one of the tubes and welded.

All in all it came up pretty good, very fast throttle response, good power throughout the rev range, although I have not compared it with a stock A15 I'd say it works very well.

If you are interested i can take some more photos of it or give you more info on how to make the tricky bits like the intersection of 2 ports into a single tube.

Good luck.

TnPShow's website has the Manifold drawings, and the Carby flange I found specs on the new somewhere...