When was the last time you adjusted your lifter rocker arms? If they are hydraulic lifters, as the cam wears the lash gets greater until they will start ticking away when cold. If the noise is up high it could be rocker arm lash slap. It is the easiest and simplest thing to check first. Just a 1/4 turn in of each rocker nut will tighen up your hydraulic lash to within specs. If solid lifters you should be checking them at regular intervals anyway...