How to make an intake manifold

First you need a design; modeled in 3D CAD

Then you need to design the sand pieces that will mold the molten metal.

Then you need to make a set of patterns (molds for sand) to form the sand mold pieces

Then you mold some sand in your patterns

Then you assemble the sand mold pieces

Now you are aready to pour the metal into the sand mold

After the pour, the sand is broken off the casting

Here is the bottom mold (the drag) after it was broken away

Keep breaking sand until the manifold is born.

Then you remove the runners, gates and risers and you have the manifold