Nothing to panic about, I’m still trying to come up with a way to make that manifold with the materials and processes I have at hand. Now I don’t have access to any 3D printers, much less anything that would allow making compression molds for intake manifold runners. But what I DO have is sheet metal, and hammers and dollies for shaping that sheet metal, and a torch that I can use to heat metal so it can be formed without wrinkles or tears.
So what I thought about was making a sheet metal mold that would mimic the actual part, then making molds from that sheet metal positive, with lots of reinforcement so they don’t collapse under the forces of compression molding. By using sheet metal to make the positive I wouldn’t have any problem with making the positive mold absolutely smooth, that’s a process I mastered decades ago. But yeah, sheet metal positive for the inside and outside molds, I can do this. It would also work for the plenum molds, especially since to swap left to right all I would need would be to turn the plenum over so the throttle arm of the throttle bodies would be closer to the center than the outside on both plenums.
The plenum will have 3 sides and 2 ends for its mold, the bell mouths for the runners will meet to form the 4th wall of the plenums. The inner finish for the plenums is not critical at all except for the entrances to the runners, which will be molded into the runners.
And I need to eat and it’s almost 2200 so I’ll have to find something I can throw into the microwave, then go to bed.