the valve is hydraulic, there is no adjustment..
Ok.. 2 thigns to do..
first, change oil filter to a quality brand, Wix, Purolator/Motorcraft, K&N, etc... NO FRAM!
2nd, there's an additive for the oil called Valve Medic, made by Gunk. pour that in (preferable with clean oil), and drive. within 200 miles, it'll work. there's another additive called Rislone, what will work also, but I trust the valve medic moreso..