This morning I cranked my 1992 D150 (was 5.2L) 5.9L (1997 block, transplanted by me in 2013) and it ran fine initially. The rpm never exceeded probably 2000rpm as I started backing it through the lot at my shop. Suddenly it began skipping violently, shaking the whole truck. I went from reverse to neutral to try and "clear it out" with a slight rev/throttle snap. Might have gone to 3-4000 in neutral, skipping terribly and not smooth at all. I finished backing it out of the way and raised the hood to listen. Loud tapping on the left bank and popping through the throttle body. After lunch I pulled the valve cover and sure enough, the rocker was cocked on #5 exhaust (it has self guiding, stud/poly-lock Crower 1.7 stainless rockers) and the keepers were GONE, the pushrod was under the intake rocker and the retainer/spring was just sitting there. The valve was in place, but stuck closed. I pulled the left head only, and the valve had lightly struck the piston, just enough to smudge the carbon off. Removed the valve and yes it's bent. These were MoPar performance heads, added by the previous engine's owner when his heads cracked. MoPar ".525" square (not beehive) springs and retainers came with the heads, with production valves and locks. Why would these factory retainers (bead type) fail and has anyone here seen this? The pushrod, Crower rocker, spring, retainer and even the valve stem (besides the bent head) look cherry, just oily. The rolled bead groove looks mint, not a scratch on it. When I get the intake off tomorrow (I hope I'll have time), I hope to find the locks to inspect them. Any ideas WTF happened??? This engine has run awesome for years, I just drove it 100mi round trip last Thursday night after work to go see a movie with a friend, and it was flawless. I'm baffled. My 2001 Durango (5.9L 2wd) has a leaking timing cover and I was going to capitalize on this time to upgrade heads (Indy/RHS) and cam/add M1 intake and mid-length headers, but now my daily has died on me. UGGH!!