Is the head already bolted down? The best approach, or at least the one that I used was to put number one to TDC as indicated on the Harmonic Balancer, then put the head in place without the cam. Place the cam in place with the TDC mark aligned against the mark on the front cam tower. Then gradually start the cam bearing stand bolts, a little on each bolt at a time. Don't tighten one or a pair of bolts down all the way, you could break the cam or strip the boltholes. Turn each bolt a turn or so, then the next bolt and so on, then start over again adding a turn at a time.

If you have a valve touching a piston it is not timed correctly.

Good luck,