Never had this problem B4 so any ideas would be appreciated! 291 heads have been redone with screw in studs & roller tip rockers, locking adjust nuts & double valve springs (Crane), Summit hydraulic cam/lifters [email protected] but when I set the valve lash cold, it runs ok for a few miles then I hear clacking. So, pulled the valve covers & set them hot by backing off until the clacking starts easing them until it stops then 1/2 turn down. By the time I get to the #7 # 1 is clacking again! Did it again & again & seemed ok then after 100 miles clacking & ROUGH idle again! Whats up???