Suburban down.

[SUBURBAN5]

Not all fasteners are created equal. A high stress component like a rocker stud needs good hardware. ARP fasteners comes to mind. Stay away from cheap junk.

The rocker arms, are they self aligning? I'm not seeing guide plates. If not self aligning they are moving all over the place with the engine running and could be creating some nasty harmonics, and therefore, the breakage.

Edit, The pushrod tip looks pretty hammered. You might want to look at the cam lobe and lifter to make sure it's not hammered as well.

One other thing I'm looking at here is how the valve spring sits under the retainer. The bottom side of the top retainer should have a step/register that centers the valve spring under the retainer. 2 of the 3 springs I see look off center as if the spring is not located or it has the wrong retainers(too small) for those springs. The bottom side spring pocket in the head looks like it was cut for a 1.4-1.5 spring but it looks like it's a 1.26 sitting on a shim. Maybe it's located on the inner diameter of the spring but a lot times you see the spring in a spring cup that centers the spring to the guide, Again, a spring walking around can create a lot of vibration/harmonics in the valvetrain. It's a pretty beefy looking spring but needs the right set up. It's best to source springs and retainer from the same manufacturer.

I don't think there self aligning. Do I get a magnet and pull the lobe off? Which part the lifter?

 

[SUBURBAN5]

Is the valve as free in its guide as it needs to be?

How would I check this?

 

[SUBURBAN5]

That's an amazingly clean break. Wonder what would make it do that?

Me too. Last thing it was doing was rattling. Then I heard a ping and heres the end result

 

[SUBURBAN5]

Is PRW considered junk?

 

[Pinger]

How would I check this?

Rough method - skelp the top of the valve with a heavy hammer hard enough to unseat it and see if it returns as it should - like it looks like it never opened.

Better version - improvise a longish rocker arm with a hole such that it can be restrained by a bolt in the boss the pivot post came out of and use hand pressure to open the valve and watch/feel for how it moves both ways.

If there's not a problem there then consider that any or all of the other pivot posts could be heading the same way.

 

[SUBURBAN5]

Rough method - skelp the top of the valve with a heavy hammer hard enough to unseat it and see if it returns as it should - like it looks like it never opened.

Better version - improvise a longish rocker arm with a hole such that it can be restrained by a bolt in the boss the pivot post came out of and use hand pressure to open the valve and watch/feel for how it moves both ways.

If there's not a problem there then consider that any or all of the other pivot posts could be heading the same way.

I'll try it . If it never opened why would be my symptoms? Engine been running for about 4plus years. Put in thousands of miles

 

[Pinger]

I'm just wondering where the force came from to snap that post (if it wasn't a metallurgical fault or some other geometry related issue - hence concern for the others) and the valve sticking is the only obvious resistance.
If the valve had been sticking though, there'd surely have been a mis-fire present.

The other possibility is at the other end of the train with play at the cam lifter end. The cam has a gentle 'ramp' to take up clearance before it gets to the actual valve opening part. If there's too much clearance, the clearance ramps don't get to do what they are there for and the subsequent sudden take up is harsh - and destructive. Collapsed lifter?

 

[SUBURBAN5]

I'm just wondering where the force came from to snap that post (if it wasn't a metallurgical fault or some other geometry related issue - hence concern for the others) and the valve sticking is the only obvious resistance.
If the valve had been sticking though, there'd surely have been a mis-fire present.

The other possibility is at the other end of the train with play at the cam lifter end. The cam has a gentle 'ramp' to take up clearance before it gets to the actual valve opening part. If there's too much clearance, the clearance ramps don't get to do what they are there for and the subsequent sudden take up is harsh - and destructive. Collapsed lifter?

Ok I get what your saying. I'll check it when I get the parts in to see how the engine moves. I'll also try the hammer method lol. What is a lifter?

 

[SUBURBAN5]

I only ask cause of right now I have a busted bolt and bent rod. Everything else like the rocker or ball looks heavy worn. I'm not sure if it was too tight or if it got loose. I'm gonna compare it to piston 2 set up to see how they look.

 

[Pinger]

If the valve is suspect, knock up something that lets you push it open by hand and if there's doubts you can do the same on another valve and compare.
Sticky valve would have put a lot of strain on the post during opening and if/when slow to close would have been noisy if not fully closed before the cam came to open it again - which further increases stresses on the valve train - re excessive clearance (lash).

Lifter bears on the cam below the pushrod. See Playing with TBI's recent posts/thread re his collapsed lifter. Given the above paragraph the lifter could have collapsed also. Subsequently or first. If so, it might be impossible to know the sequence.

For sure, I'd want to know that the valve isn't sticking or there's a repeat performance coming. Maybe the piston will join in on the encore. What a finale that will be!