engine is fresh rebuild, with a few hundred miles on it. I adjusted the lifter and added the new locking nut. The car warmed up fine, idled fine, ran fine and once fully warmed up screamed it up to 6000 RPM's a few times sound great. Hopefully problem solved. That was the only valve that loosened up. i have to say one thing, I own many cars and have owned many other new an old, THE 302 Z28 MOTOR IS BAD ASS,not only is the car stunning to look at, the motor is so revvy and smooooooth. Thanks for all the help, lucky to have this site.