Electronic Discharge Machining or EDM for short is a process where an arc is struck between the electrode and the base material to burn away the unwanted areas to the same shape as the electrode you've created. This act takes place in submerged in a dielectric bath to dissipate the heat and flush away the burned material. The process is more time consumming than conventional machining techniques but you can do things that cannot be done with regular machines like, intake runners.
  Picture to the right shows the Easco Sparcatron. It's setup like a conventional mill but has some features to help position and locate edges, dither and audible sensing. Dither is used to set your Z axies by moving the automatic ram down to the part and when it touchs, it stops. The audible features are used for locating X and Y positions, when touching the part, it makes a beep.
  I started experimenting with some aluminum blocks and a basic electrode to get the setting right before creating the final product.
  The photo to the left shows the electrodes to make the desired shapes for the intake runners. On the left and right are the side runners and in the middle, the boost port runner. I'm using aluminum as a holder for the graphite electrodes that were SUPERGLUED on for ease of holding and machining on conventional and CNC machines.
  Careful planning is needed because the procedure has to be entered in through the linner bore and it gets awfully tight in there and you can't view the operation when machining.
  To the right shows off the finished test, I've sectioned the part to get a better view  and picture.