If it was quieter before and this noise is new
It might be your lifters are dirty internally
Or just giving up.
I agree with Rusty on fast rate cams being noisy.
The comp XE 268h in my 340 is like a sewing machine running.
I've also put 3 sets of lifters on that cam over the last 5 years.
Because of lifters problems.
I'm done with hydraulics!
Just bought a solid flat lunati cam
And Howard's edm lifters..
Mike