Doesn't sound too good really
Using a large screwdriver pressed against your ear as a makeshift stethoscope might help you localise the noise or get a better idea of the makeup of the noise.
If it is a head problem there is no easy way to diagnose the extent of the problem without removing the head.
You could compression test which would tell you which cylinder is the problem but its still head off job to investigate.
Blown a ring or dropped valve?
