Have you enabled the UART port on the pi?
You need to update the pi's boot script to do this. Checking back in the forums, I find these instructions:
Also,
1) If you use a 8mhz arduino, these run on 3.3 volts, so you dont need the level converter.
2) If you use the arduino software serial library, this lets you continue to use the built in serial on pins 0 and 1, for uploading and debugging your code on the arduino side. Makes things easier to develop. https://www.arduino.cc/en/Reference/softwareSerial
