Thick oil to solve valvetrain noise?

When you have the valve cover off, start the engine and let it run at a slow idle. Run a .010 (or so) feeler gauge between each rocker and valve stem to determine which valve is causing the problem. The tick will lessen or go away when you find the bad one. Inspect the rocker arm socket, bearing surface, push rod end, and rocker shaft for wear. If they look good, it's probably the lifter and cam lobe that're bad. Depending on which one it is, some of the lifters can be pulled without removing the intake. A good magnet or magic fingers can sometime remove them if it's not too mushroomed over on the cam end. If it's bad, you can try putting in a new lifter for a temporary measure but they usually won't last long. When you get around to replacing the cam, use some oil with a higher zinc content to help keep it from happening again. 20-50 works fine on those motors....probably won't help the tick much though...