i just replaced the piston rings and vals on the head now it wont start i checked the fuel pump its working im getting fire and the timing is set yet it wont start any ideas ?

On mine the head timing marks did not line up or at least when lined up it did not run then I moved the mark over a little and it did run but idle was up then down, up then down so I moved it a little more then it ran perfect, this was after doing a rebuilt head, I lined it all up after top dead center on lower end & also had put the timing belt on so afte rit did not run I undid the belt and turned the head one position on belt then another. I know this thread is older but it may help someone out in the future.