I've just fitted a rebuilt bottom end and a second hand head to my RST. I was assured the head was good with no knocks or rattles but I have a knock I've had con rod shells fail on me before and it sounds very much like that noise but the bottom end has just been rebuilt so can't be that (I hope) Is it possible to take the cam out of the head without taking the head off?

Help me please I'm running out of faith