About a month ago, I had a timing problem. and had a supposed "expert" mechanic looking at my truck. We ran it with the valve cover off to see what the valves were doing. he heard the click, and he said they were way too loose, started messing with em. It didnt change nothing. Well I put it back together, got it timed, and had a horribly loud clack clack clack. I drove for about 20 miles, tooke the cover off, and low and behold, my expert mechanic had left one of the spacers to the rockers off, my rocker wasnt hitting the tappet at all, contacting the side of the valve to open it. Found the 2 halves of the spacer sitting right there in the head. Put em back on, adjusted my valves myself to spec, and Im back to having my tick of reliability. never heard one that didnt do it.