Thought I might get lucky, guess not...

[typ4]

That is definately a valve or spring problem

 

[91f2504x4]

My truck made a very very similar sound when a rocker arm came loose. There was actually a few loose so I went through and retorqued them all and it was fine after that, my engine is fairly low miles too, but it had been used to pull big loads it's whole life and was in a very bad accident with a tree right before I got it.I have since tore it down and put all new seals, gaskets and a few other upgrades in the motor, and it has never had anymore problems. I am not sure if someone had the motor apart before or if it was caused by the wreck or what. The truck the engine was in used to be owned by a family member who used it with a gooseneck almost non-stop.

 

[6 Nebraska IDIs]

I pulled all of my rockers and pushrods out. None of the rockers were loose, actually most of them were excessively tight, even my standard length 1/2" breaker bar wouldn't break allot of them loose without a pipe on it.
None of the pushrods were bent.
I'm hoping to get some time to work on it tomorrow.

 

[6 Nebraska IDIs]

Well, I reassembled it with all my new 7.3 rocker arms and new push rod set, started it with no valve covers again. Started harder than ever, almost like the timing is changed or something, hardly even ran at first, almost like 100rpm, had to hold the throttle open a bit to keep it running. Valve noise was going at it again, smoke just rolling out the exhaust. Finally got the motor to run on its own went around and started cracking lines. One had no effect at all, others slowed the motor down, one almost seemed like it helped though. But only after I'd closed it back off did I hear any effect, the noise started to quiet and almost went away then it came back worse than ever. I wrote it off and moved onto the rest quickly cracking and closing them and after nothing else happened sat there in wonder of what could possibly have gone on with it going away and then coming back worse.
I revved the motor just slightly to see if it smoked worse, it did. But in the middle of the throttle blip my brother and I both heard a loud BANG inside the motor, let it run a little more to see if it did it again, it did, BANG almost like a carb backfiring but it was inside the motor not in the intake or exhaust. Shortly after the chuff noise at the rate of a single valve opening and closing every second or so turned into a cuffchuffchuffchuffchuff like the valve had completely dropped (no visible signs of it though) or it was now on more than one cylinder (highly unlikely).
At this point Im afraid of running it any more. Last thing I want to do is actually blow the motor.

 

[BigRigTech]

Chuff chuff is usually a rocker or push tube out of place/broken and the banging is likely a backfire into the intake manifold....Any signs of a dead/broken lifter?

 

[6 Nebraska IDIs]

Well the push rods are all straight, rockers are perfect condition. All are moving what appears to be the same distance too.
I tried my best to check and recheck the pushrod placement to ensure they were seated into the lifter properly.

 

[typ4]

It ran rough on startup because the lifters traveled up and the valve springs didnt have time to push the oil out to the proper operating level.

Pull the intake and valley pan, check the lifters to see if one isnt broken. the cylinder that makes no difference may have a cracked,chipped, bent valve. Bad guides,weak spring. Best to tear the heads off, disassemble and do a complete inspection so it doesnt self destruct.

 

[6 Nebraska IDIs]

That's what Im figuring Im pretty much down to, if thats the case it will have to wait until next summer/fall.
Im going to do a compression check on it next weekend, but other than that Im probably done with it. Don't have the money to do a complete tare down this year.

 

[typ4]

Git that thing apart ,we cant wait that long to know what carnage awaits. I know you have extra lifters

 

[6 Nebraska IDIs]

Yea, lol I do, but I only have 15... someone missed one. lol

I only tore into this thing hoping I'd get lucky and it would be something simple like a bent push rod, got my hopes up on that after I didn't see any broken valve springs or hanging/bent valves. Now with all the new possibilities, I'm probably just going to wait to do what I had originally planned, tare it all the way down, have the heads completely rebuilt, install my arp studs, turbocharger, moose pump, new injectors, intercooler, etc etc. Im the type of person that doesn't like to half ass anything. I was making an exception here hoping to luck out so I'd atleast have some wheels.
Guess I'm still tagging along with my bro... for another year.

 

[Diesel JD]

Might be a flattened lifter or the camshaft itself has gotten beat up.

 

[Michael Fowler]

The way you describe the sound going away, and returning in a few seconds suggests to me a lifter issue. Sort of like when adjusting hydraulic lifters on an early SB Ford ( 260/ 289).

 

[BROWNIEBOY525]

in your vid it sounded and smoked the same way my uncles truck did when it dropped a lifter

 

[6 Nebraska IDIs]

Hmm. Lets see if we can get a few more people thinking lifter before I pull the IP, intake, and $65 valley pan.
At this point I REALLY want my truck back, I have so many thousands of dollars in parts already waiting here to go into the thing, but just don't have the money for the complete tare down right now.
It was so weird how the thing ran so much worse after installing the new pushrods and rockers though.

 

[typ4]

If y ou were closer I could rebuild the heads pretty reasonable. Ya know you might pull the rocker covers back off and check the stiffness of the weak cylinder. you might just have a sacked spring, that usually means a bad exh guide but not always.
And I of all people know about not doing things half assed.
On that note, I reused my valley pan and have had no issues.