If it is a hydraulic camshaft and you have adjustable rockers, it will need two turns to get plunger in center of travel. With a new lifter, no oil in it, from zero preload it takes a little over 4 turns to bottom out plunger, so center of travel is 2 turns. If you don't get the plunger near center of travel they sometimes have trouble filling with oil, you will have a noisy couple for the first bit of driving for the day. If it is a solid lifter cam you will be using a feeler gauge, .016 to .032 depending on camshaft, recommended lash is on the cam card.