There is no adjustment on the 3.7, 4.7, 5.7, or pretty much any motor chrysler has made in the last 20 years.
The 4.7 is a SOHC motor, so the valve lash is maintained by the lash adjusters. They act like hydrauluic lifters, inflating with oil to automatically adjust lash.
More than likely it's an oil issue. Have you checked the oil level? what viscosity are you running? last time you had it changed? Oil pressure look good on the gauge?
If all the above check out, and you suspect you have a bad lifter, pull your valve cover and rotate the cam until the valves are closed for one cylinder, and press on the lash adjusters. Should be firm, if they collapse easily or feel spongy they need replacement.