gigabyte h87m-h3d

Hi all my first post, just built a gigabyte H87M-H3D with Intel core i5 3.2Ghz quad into a power mac mirror door mod. Everything is in, SL is on using multi beast, issue I'm having are: machine boots goes to tonymac screen loads then resets straight after apple logo screen. Osx 10.6.8 not...