Rocker arms loosening 93 5.7 tbi

[A97obs]

Having some major engine occurrences rocker arm noise on a road trip Today .
This 93 tbi ran good and runs good but i am running into a repetitive rocker slap that i find has happened twice and it happens on a start not while running.
I pulled the valve covers with neighbor and we found the 2nd back from front passenger side rocker arm ( seemed) excessively loose . I removed the arm check the push rod , wasn’t bent , I slipped it back in and made sure it rested on the lifter and tightened the rocker nut back down until it slowly took away all the (ticking) with truck at idle Very slowly !
And then I did 1/4” turn extra. I let the truck run idle sounded A1 perfect

I went to go to a few stores shut the truck off once and was fine then one more time and on start same rocker noise came back in 15
Min of drive time and maybe 2 miles

Might I have a bad rocker arm lock nut? Or could this be a lifter issue. Like mentioned first attempt to fix it seemed successful due to tightening the play out of the rocker arm ………. but the amount of threading left compared to the rest seemed off

I read this post about this issue “quote”

If you haven't done a lot of adjusting yet, you can compare the amount of threads showing to see if the nut has come loose. I've re-used zillions of those adjuster nuts, never had a single one back off on it's own. Aftermarket Poly locks are another story. Adjustment- engine running Loosen until the rocker clicks Tighten until it stops Add 1/4 turn and pause, wait till the idle smooths out Add another 1/4 turn, for a total of 1/2 turn Move on to the rest When you're done, compare the threads that are showing on the studs, they should all be about the same. Too many threads, probably collapsed/stuck lifter. Too few threads, receded valve.

 

[rebelyell]

Yes, you may have bad threads in nut and/or stud.

Another possible cause May be rocker arm stud pulling out from head --- like virtually all OE GM iron heads, RA studs are a press-fit into head --- very few OE iron heads have OE threads.

Also, check Both ends of PRs to confirm they are not fracturing & collapsing in on themselves.

 

[A97obs]

This is my daily drive just freaking out.. I’ve never had this happen on my other tbi motors over the years , nor any of my 96-98 year vortecs I’ve owned .

Initially I thought it was a sticking lifter I’ve had that happen on my Vortecs. But when I found the issue at least thinking it was the loose arm , then for it to repeat itself right away? That’s when it got strange . And only when I shut off and start the truck. And even my neighbor said
(Weird) look at the remaining extra threads on the nut all the arms that were working good had the same fame as the bad one. That was weird but yet still tightening that arm little by little slowly did away with the tapping .
What do you think the chances are here ? I wanna hope it’s a nut that’s lost its grip .Can I try a local hardware store or are these special specific ? What about if I use two and one and a jamb nut ? Thread locker?

 

[A97obs]

Also, check Both ends of PRs to confirm they are not fracturing & collapsing in on themselves.

This ? How would a solid rod collapse in on itself help me understand that statement . And it Can’t must not be a lifter issue if when the initial tightening of the arm the noise went from Noise slap tick to Zero noise . Is that an indicator the lifter at least is operating fine? I would hope . I’d prefer to only have to deal with the rocker pr and or stud issue without yanking the entire head off
What a nightmare this is for a such a recent purchase and considering how well it runs and drives and this intermittent issue just ruins it all

 

[PlayingWithTBI]

I wanna hope it’s a nut that’s lost its grip .Can I try a local hardware store or are these special specific ?

IIRC they are a 3/8"-24 "Stover" style nut meaning, not quite perfectly round. That's what keeps them from unscrewing. I'd try new rocker nuts before doing anything else.

How would a solid rod collapse in on itself help me understand that statement

Push rods are hollow so the lifters can pump oil up to the rockers.

 

[Schurkey]

Yes, you may have bad threads in nut and/or stud.

Possible. Not real likely. How stiff was the nut when you tightened it? OEM nuts are crimped pretty hard, they're stiff when turning due to friction.

rocker arm stud pulling out from head --- like virtually all OE GM iron heads, RA studs are a press-fit into head

Check the height of the suspected rocker stud vs. the other seven on that head. The height of all eight rocker studs should be reasonably even. If your "problem child" stud is higher than the others, it's pulling out of the cylinder head casting.

I found the issue at least thinking it was the loose arm , then for it to repeat itself right away?

Maybe a bum nut. Maybe a stud pulling out of the head. Maybe a collapsing lifter.

MY guess is a failing cam lobe/lifter bottom.

 

[A97obs]

Push rods are hollow so the lifters can pump oil up to the rockers

That makes sense but them collapsing in I wasn’t understanding.
how that could virtually happen .
It’s such a crazy situation never expected or experienced a cylinder head sorta failure. And this is my daily A-b work commuter. It was promising outcome the first fix but to have it happen in another 5 miles of driving was odd. I was trying to think of this being a prior issue on the truck another words probably the previous owner had this happen and freaked out and said time to sell ‘

So the nut being weak ( threads ) not staying locked and the mechanical force and speed of the rockers can and do cause these nuts to back off if they’ve been adjusted one to many times?
I am going to measure the pr length compared to the 3rd pr and I’m going to try and count threads . The only part I didn’t like was seeing the thread count the same on the loose rocker as the rest it indicated the nut was as tight as the rest at first glance . After I tightened it enough to alleviate the noise, the thread count left coming out of the top of the stud visually looked more then the other rockers studs.
I’m gonna be in a pinch if I have to change the head over a stud pulling out ( failing)

Any idea where I can get that (stover) nut for the oe cylinder head? Locally I’d hope but it’s probably a performance part online store thing
Would it be worth buying a set.

 

[PlayingWithTBI]

The only part I didn’t like was seeing the thread count the same on the loose rocker as the rest it indicated the nut was as tight as the rest at first glance . After I tightened it enough to alleviate the noise, the thread count left coming out of the top of the stud visually looked more then the other rockers studs.

If that's the case, as @Schurkey said either the stud is pulling out or your cam and/or lifter is/are wearing out! Not an unknown issue with flat tappet cams! You're gonna have to pull the intake manifold to get at the lifter(s), pull the suspect one, and check it against another one. Then shine a light down the lifter hole and look at the cam for wear. When/if reassembling, put the lifters in the same holes that they came from!

 

[Road Trip]

Might I have a bad rocker arm lock nut?

As stated previously by the subject matter experts, here are the 4 ways for excess clearance developing > noisy lifter operation,
from best to worst:

1) Self-locking nut has insufficient 'running torque', and backs off during operation.
2) Pressed in rocker arm stud starting to pull out of the cylinder head. Easily found by laying a straightedge
across all 8 rockers arm studs and looking for one that's taller (& noisier) than the others.
3) Bent pushrod from floating valve making contact with incoming piston. (Pushrod acting as affordable
mechanical fuse.) Usually older weak valve springs are the root cause, caused by a rare passing maneuver
(dad) or overenthusiastic operation while out & about. (lad)
4) Cam lobe wearing away or bottom of lifter wearing from a slight crown to a concave face. Bad juju.

****

To prove that I don't always favor the worst-case scenario, maybe you will luck out and you have
a self-locking nut that's backing off. If you are willing to spend ~$1, you get get a new one of
these and see if it A) Threads on with a noticeable difference, (increased effort) and B) once
you get the lifter just quiet (plus that 1/4-1/2 turn of preload) ...will it *stay* quiet?

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Fingers crossed it's the $1 fix. But be on the lookout for the 3 other possible failure scenarios.

Best of luck --

 

[A97obs]

Fingers crossed it's the $1 fix. But be on the lookout for the 3 other possible failure scenarios.

I’ll be at it tomorrow first thing ‘ I’ll update with the findings.
Nothing like going from needing minor emissions work and a ps pump thinking everything is gravy to possible engine failure ( top end )
It’s just the gamble we take on purchasing old rigs . I suspect this was in issue prior , they couldn’t resolve it or determined it was one of the other three worst scenarios and just tightened up that stud and sent it on its way smh.
I’ll fix it regardless what it takes . The bones of the truck are worth it to me being in its shape and surviving the decades.

Question ? What is the best case scenario fix if the stud is pulling out ? So I end up needing a replacement cylinder head? Or at that point would I be better of doing a performance head swap with updated rocker design that would do away with this issue …The lower end is 140k with good compression might be worth it