Howdy Back Matt and All:
I'm betting that you have a/some sticking hydraulic lifters that are making noise. What year engine are you working with? Any modifications?
If the noise is coming from sticking lifters you have three options;
1. Use a high detergent additive to try to chemically clean, loosen and remove the varnish that is causing the sticking,
2. Add adjustible rockers to take the slack out of the noisy rockers,
3. Replace the sticking lifters.
These are listed in least to most expensive/labor order
Another possibility is that wear has added clearances beyond the range of the hydraulic lifters. How many miles are on this engine? If that is the case you might be able to tighten things back up by using a .060" longer pushrod from Pioneer Performance Products.
At the very least plan to disassemble the rocker shaft from the head for a thorough teardown, cleaning and inspection. Oil to the rockers comes up through the back stauncheon and passes through the shaft to the very front rocker. The system frequently gets plugged and will not allow oil to the front rockers causing excessive wear at the shaft and at the pushrod cup and ball end. There is a stickie at the top of this forum on this.
Give us some feedback please.
Adios, David