New cam...loud clacking lifters. ???

Thanks for reply's, oil pressure when hot is 20@idle, 40+ just off idle, and up to 60+ from there... timing is right on, starts with a touch of key, idles nicely, sounds great at the exhaust, shafts are correct, ran with v.covers off...plenty of oil @ the rockers...only bent 42 yr. old push rods when first started, both sets since are fine.