07 valvetrain knock

bought an 07 1/2 ton crew cab new body style yesterday. throwing a PO304 Cylinder 4 misfire. horrific knocking noise is coming from the head/valvecover area. the guy i bought it from said the chevy dealer told him it was a lifter bad. any guesses/suggestions. i have searched all over this site and others and not finding much. i will be tearing into it this weekend and just thought i would see if anyone can guess what it is before i open it up. the truck is 4x4 with 125K. still holds 45psi oil pressure at stop sign and does not have any vibration or balance issues

Sounds like one of the DOD lifters failed. If you plan on keeping DOD, replace with a DOD lifter. If not, have DOD turned off in the tune and replace with ls7 lifters.

replaced it with dod lifter, ran it for 2-3 minutes and ran good and quiet. changed oil and started it back up. ran for another 5 minutes and it did it again. same lifter just as loud. thanks for the reply pl4boy. any suggestions. i live just south of the kc area and i called a shop around here who does ls motor work(mainly car) and they suggested the o-ring on the bottom of the valley cover could be causing a lack of oil pressure. any help would be provided

What's the rocker like? How about the pushrod? Bent maybe?

rocker and pushrod both looked good when i had it apart

Have you found the problem yet?

so i pulled the gasket off the valley cover. it was obviousoly blown out. replaced it with a new one and still rattles. thinkin i have an ioling issue. think just gonna throw a motor in it