Originally Posted by pizzi-man

Zero lash is when the push rod makes contact with the lifter and there is no play between rocker and lifter via the push rod. If your not paying attention you could be colapsing the lifter and then putting an additional 1/4 turn is way too much. Loosen the rockers and then tighten them down while lifting the rocker off the valve until you can't lift the rocker. Then your at zero lash . Now it's your 1/4 turn or 1/2 turn to preload the lifter.