.020" preload won't work if you're not using a race hydraulic tappet. plunger travel in the tappet should be around .210". the preload needs to be around 50% of plunger travel. if you have adjustable rockers with 3/8"-24 thread adjusters set the preload between 1 1/2-2 turns. that will give you somewhere between .060"-.090" preload. treat .060" as a minimum. factory pre-load with non-adjustable rockers was at least .100". a performance hydraulic cam will make a little noise due to the fast closing ramps and that can't be adjusted out. setting the preload to .090" should make a noticeable difference.