So I've been trying to diagnose a valvetrain tick or clattering noise that I have in my 5.9 magnum under certain conditions. I can say with certainty that it is NOT pinging. I've had pinging issues in this truck over the years and know that sound well. This is most certainly a clatter in the valvetrain...or possibly an exhaust manifold leak, although I am growing more doubtful of that second one. The clatter is RPM dependent.

178k on the engine. Had the heads off and full valve job done about 20k ago. Everything else is original.

Conditions under which it clatters
1. Oil is warm or hot. It doesn't clatter at all when the oil is cold. It does NOT tick on startup...which is confusing me. I would think a leaky lifter would bleed down and tick on startup.
2. 2500+ RPM. It doesn't clatter at idle or low engine speed. Only higher revs.
3. It is most pronounced when the engine is not under load. So for instance if you kick the overdrive off at highway speeds, and then let off the accelerator (revs come up and produce some engine braking) it clatters very loudly.

So far I have I used a stethoscope and think I've got it pinpointed to the driver side valve cover. I can hear it loudest with the stethoscope touching the valve cover, and I can slightly hear it when touching the exhaust manifold. I also idled the engine with the valve cover off and felt all the rocker arms and springs as the service manual recommends...all felt the same, and all seemed to be oiling equally. I didn't want to rev the engine up to an RPM that makes the tick with the cover off because that would make a huge mess. I verified that the driver side rockers were all torqued and seated correctly, and none of the pushrods are bent. I haven't had the passenger valve cover off yet.

Anyway, just thought I'd post this to see what ideas other people had. Don't even start with the plenum gasket. Everyone on the forums wants to blame every issue on the plenum and I assure you the plenum is not the issue here. I replaced it with a thick aluminum plate and shorter bolts with loctite a couple years ago, it's fine.

My current theory is that I have a lifter that is just starting to fail. It can maintain proper lash when the oil is cold and thicker, but when the oil heats up and thins out it starts to bleed a little pressure off and allow for some clatter in the valvetrain.

 

And you don't have an adjustable valvetrain..... One of the things I don't like about the magnum engines.

So, it's either a lifter or two going bad, or, things have just worn to the point that the lifters can't take up all the lash any more. (though, one would think, that would be noisy under more circumstances.....)

 

It's curious isn't it. I mean it really doesn't sound like your standard lifter failure situation. I mean the conditions under which it clatters (and presumably it would do that by failing to maintain hydraulic pressure) are when the oil pump is producing maximum oil pressure. Also, when the engine is under load...no clatter. Like if you mat the throttle and run it up to redline...nothing. Or I should say, you can't hear it. I do have a delta 40 flowmaster dual exhaust on the truck that makes a reasonable level of noise.

Idk, I've been looking for a reason for years to build a 408 for this trunk, maybe I've found it...haha

 

What oil is in it and what kind of pressure do you have after it warms up?

 

Kirkland full synthetic 5w-30. At operating temp I've got probably 30lbs at idle, 50-60 lbs basically all rpms above 1200.

I put some 10w-40 in it just to check, and it didn't solve anything, just made the clatter sightly harder to hear.

 

So, I'm reviving this thread because I want to tackle this issue. The truck has been off the road for a while as a prepare to do the body work and paint, but I still would like to have it driveable just in case and the ticking is pretty bad now, so I find myself not trusting it.

Symptom Description:
Loud clattering noise that sounds in sync (speed wise) with the valvetrain, not the crank or drivetrain. Only able to hear it under deceleration or very light throttle conditions when the revs are over ~2200. When reproducing it over and over, there is a little bit of variance in it, though it's about 95% in sync with the valvetrain. Cannot be heard at idle (except faintly with a stethoscope through the driver side valve cover). Very hard to hear when the engine is cold, worsens as the temperature rises and the oil thins.

Video:
Attempted Diagnosis/Repair:
First thing I did was pull off the valve covers, rockers, and pushrods to give them a visual inspection. Everything looked okay, so I assumed it was lifters. A few months back I tore the top end apart and replaced the lifters with used lifters out of the core motor I bought to build into a 408. I disassembled, cleaned, and tested each and every lifter before installation. Buttoned it back up...still ticks. I noticed that the original lifters were really hard to remove from their bores. I probably should have tried to polish up the lifter bores before putting the other lifters in, but I didn't, and I don't recall having to force the "new" lifters into the bores, so I don't think they are sticking.

This evening I took the driver valve cover off again, removed the rockers, and did another thorough inspection. Pushrods are all straight and good, not clogged up. Rockers, pedestals, and springs all appear to be just fine. All the lubrication veins are in the correct orientation. I thought I had found it, as one of the pedestal retainers had some wear in it, potentially allowing some rotational slop in the cylinder 1 rocker arms, but after replacing it with one off the core motor that was good and tight, buttoned it all back up according to the service manual instructions (v8 to TDC mark, 21ft-lbs)...the tick continues.

I'm really not sure where to go from here. The timing set is a double roller that is only a couple years old and probably has less than 10k on it, so I don't think it's that. It doesn't happen at idle or upon startup after sitting, so I don't think it's an issue with lifter bleed down. It doesn't happen at idle and is slightly irregular in it's sound, so I don't believe it to be an exhaust manifold leak. It's too clattery and fast to be a rod knock. I don't think it's a wrist pin because people say that happens worse on acceleration, while this is silent on acceleration but clatters when the engine is not under load, particularly in situations where the momentum of the truck is pushing up the revs.

I'm not sure where to go from here. Sounds like there's just slack in the valvetrain somewhere and it's hammering...but I can't figure out where.

 

Was the noise there before this? When you replaced the lifters did you inspect the cam lobes?
This makes me think it's not a lifter/valve train issue. Have you looked at the converter bolts/cover?

 

Nope, no noise before or directly after. It didn't start ticking until a few years later (truck doesn't see a ton of yearly mileage).

From what I could see of the cam through the block access holes, there appeared to be some mild pitting on some lobes, similar to the cam I pulled out of the core motor, but no lobes that were grooved or wiped out.

I haven't looked at converter stuff yet. I'm doubtful though because again, the converter is turning at engine speed, not valvetrain speed, so the sound speeds don't match. Also, with my stethoscope I can hear it pretty clearly through the driver side valve cover and exhaust manifold, which I wouldn't be able to do if it were converter.

 

Ugh, I now think it's a rod.

Played around with the RPMs while it was parked and got it to clatter at 1800rpm, so I held the throttle open with a block of wood and went poking around. Could hear it very clearly on the driver side with the stethoscope on the exhaust manifold, and even louder on the heat shield for the motor mount. Pulled the number 1 plug wire, no change. Pulled the number 3 plug wire...and it stopped clattering.

 

That is NOT a good sign......