I have the same issue with my lifters/rockers making noise at high rpm's. I think my issue is with a "weaker" lifter or my pushrod length needs to be checked. I am learning as I go and can let you know what I found out. Do you know if yours is correct? what cam, rocker, push rod are you using? I am running an F cam, stock ford lifters, 1.6 FMS rockers with a stock push rod length. LMK