On to other items of need and interest in this project. Got to have elbows and T fttgs. Broke down and bought the tap and dies for 1/16-27 npt. Work well on the brass and bronze. Anyhow, the process.
Drew up some elbows and T fittings in groups of 3 contiguous fittings in Fusion360. It has a nice feature of splitting something into parts on any given plane you choose. For molding at home in sand there is nothing less expensive nor as simple as my process. Years of trial and error and still improving. Mind you these are for 5/16 brass pipe, not large stuff.
Printed out the halves on 3d printer using PLA. A touch too small to effectively use drawn in locators and time consuming to get the different sizes, so just drilled some holes for 1/16 pins to hold each half during the casting. Did two groups of castings this morning and used brass with a touch of zinc added as it has been melted several times. That was very nice to work with, not as sticky as brass can be. Had previously cast the T's in bronze.
Not sure how many I will need in total for fuel and cooling at this point. It took all day to cast, clean, drill and tap them all. (and clean the mess from it all)