Dropped valve??

Bighead440 · Nov 25, 2019

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!!

RustyRatRod · Nov 25, 2019

Damn. Not the Viper truck! I've seen some of those self guiding rockers have wings that contact the retainer first instead of the valve stem. Did you look at "all that"? Did you see evidence of the retainer actually failing or could it have been unlocked by the rocker?

Bighead440 · Nov 25, 2019

RustyRatRod said:
Damn. Not the Viper truck! I've seen some of those self guiding rockers have wings that contact the retainer first instead of the valve stem. Did you look at "all that"? Did you see evidence of the retainer actually failing or could it have been unlocked by the rocker?

Yep that one. None of the guide "wheels" (pizza cutters) are touching on the other 15. The valves and keepers are production items, and these Crowers are drop-in rockers, used by thousands without incident I'm sure. Something had to happen, but I just drove it to Dublin and back at 75mph last Thursday without incident and it fails on a cold start this morning? I didn't start it this weekend, I was gone to Moultrie in the Jeep in case it rained. The retainer looks 100% cherry and I haven't found even a sliver of the keepers yet. I may find something in the valley once I jerk the intake.

RustyRatRod · Nov 25, 2019

SO the rocker was touching the retainer first? And none of the rest. That's weird. Have you compared that one retainer to all the rest to see if maybe it's offset is different? I hate those self aligning rockers. I won't use them just for THAT reason.

Bighead440 · Nov 25, 2019

RustyRatRod said:
SO the rocker was touching the retainer first? And none of the rest. That's weird. Have you compared that one retainer to all the rest to see if maybe it's offset is different? I hate those self aligning rockers. I won't use them just for THAT reason.

Nothing appears to have been touching the retainer. Everything looks new and oily, that's it. The valve has a nice short sweep pattern clearly visible on the intake side of center, but not off much from perfect. Just NO LOCKS, they floated away in the oil I guess.

RustyRatRod · Nov 25, 2019

Bighead440 said:
Nothing appears to have been touching the retainer. Everything looks new and oily, that's it. The valve has a nice short sweep pattern clearly visible on the intake side of center, but not off much from perfect. Just NO LOCKS, they floated away in the oil I guess.

Strange. I would rotate the engine and watch the rockers through their sweep to eliminate the possibility that the rocker unlocked the retainer "somewhere" in its travel.

I wonder if maybe the valve locks just "failed"? How does the valve look where the locks wrap around it?

Bighead440 · Nov 25, 2019

RustyRatRod said:
Strange. I would rotate the engine and watch the rockers through their sweep to eliminate the possibility that the rocker unlocked the retainer "somewhere" in its travel.

I wonder if maybe the valve locks just "failed"? How does the valve look where the locks wrap around it?

Like a brand new valve.

Oldmanmopar · Nov 26, 2019

Check to see if the underside of the rocker was catching the retainer or spring edge. I have see this on many rockers even T&D. Standard 340 stamped rockers are clearanced . If you compare them to 318's you will see the difference. We just saw this happen to a set of Indy heads with T&D. When ckecked at HTA's shop while they were building our engine 8 yrs ago No. 1 cyl. was good . But when we took it apart the rest were all over the place. My son had to make a fixture and clearance them when refreshing the engine. The rockers were hitting the springs. We were lucky, The keepers were no good but being 10's they didn't let go. The push rods were also gulled due to not having a ball end. Some things are always overlooked