Think about what you're saying - shimming it raises the rocker - that will make the gap between pushrod and rocker even greater! You don't need to shim it if the pushrod is already too short to close the gap. You need to LOWER the rocker down onto the pushrod or get a longer pushrod. You might try removing material from the bottom of the pushrod fulcrum until you get the rocker low enough to close the gap AND preload the lifter. Be careful....