6.0 Cracked rocker questions

[powerstrokeboss]

Just rebuilt my 6.0 with various performance items including high rev valve springs and a stage 2 cam from dynamic diesel. It now has about 1000km's of careful break in driving under its belt. But on a trip to Seattle to visit some buddies, I cracked a rocker. Now I'm wondering first of all if it's safe to replace just that one because I know this isn't a super common problem, and secondly if there is any way of getting the rockers with the metal retainers anymore as I've read they are better, and finally if I was to replace them all would it be safe the undo the head studs one by one now that my head is fully seated.

Appreciate the help.

 

[DEEZUZ]

The retainers serve no purpose Besides aid in assembly.

Did you have the valve guides measured? Only time I've seen broken rockers is when valves seized in the guides due to excessive wear or over rev

 

[powerstrokeboss]

The head was fully rebuilt by a local machine shop and I turned the motor over to find the issue and the pushrod was moving flawlessly, the rocker cracked at basically an idle. My guess is misalignment when they were Installed.

 

[6.0 Tech]

My buddy had the same thing happen on his. He ended up breaking 3 in total. Turned out when he bought push rods and lifters, he got 6.0 length push rods and 6.4 lifters which fatigued the rockers, as when iy first started we had some hanging open. After the third one broke, we put all "new" ones in. Turns out the 6.4 rocker arms themselves are the same as the 6.0 ones, and I had a few sets laying around..

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[powerstrokeboss]

I see.
the lifter and push rods are from dynamic diesel, and the rockers are the original 2004 f350 set, so unless dynamic screwed up, I cant see that as the problem

 

[Zeb]

The only time I’ve seen a rocker break on a 6.0 is from piston to valve contact. I’m not saying it couldn’t be the valve guide, but incorrect piston protrusion, or incorrect valve recession, or over reving one, is a lot more likely.
I ran a Straub cam in my Excursion and it had a big lsa and a lot of duration. I hated it, and when I took it out I had valve marks on a couple pistons and several cracked rocker arms.
Put it back together with an RCD Stage 1 cam, and 1 head had valves that were .005” under the specified minimum factory spec for valve recession. 14,000 miles later it broke 3 rocker arms on that head.
3rd time around now. Colt Stage 2 cam, Motorcraft lifters, 6.4 length pushrods, correct valve recession, and all new 6.4 rocker arms.
Also had a Straub cam in a 6.0 that sled pulls regularly. That thing would break rocker arms on a regular basis. Pulled it apart to swap in a Colt cam, and it had valve marks on multiple pistons.
I don’t want to be all doom and gloom, but in my experience, if you’re breaking rocker arms on a 6.0, you’ve got underlying issues.

 

[powerstrokeboss]

When I assembled the motor I checked all my piston protrusions and did a fully piston to valve check with plasticine. It was close but within spec. The weird thing was it happened when it was cold, at pretty much idle, just down the street from my buddy's house.

 

[Zeb]

When I assembled the motor I checked all my piston protrusions and did a fully piston to valve check with plasticine. It was close but within spec. The weird thing was it happened when it was cold, at pretty much idle, just down the street from my buddy's house.

That’s exactly where my exhaust rocker broke.
I was sitting, idling at a fuel pump, fueling up, when it broke.
Is this an intake, or exhaust rocker? Mine were all exhaust rockers.
What was your piston protrusion, what was your valve recession, and what are the cam specs?
Also, how did you do your piston to valve clearance measurements? It’s pretty complicated to do correctly on a hydraulic lifter.....

 

[TooManyToys]

........
Also, how did you do your piston to valve clearance measurements? It’s pretty complicated to do correctly on a hydraulic lifter.....

I don't think that's ever talked about, you would mind explaining?

I've done it with solid lifter motors.

 

[Zeb]

Disassemble the lifter, pull the internals out, and I cut a bolt to the correct length so that I could just get the cup and retainer back in. You’ll need two lifters done that way. Essentially make it a solid roller lifter.
Then you need a set of adjustable pushrods.
I then pick the cylinder with the most piston protrusion and try to pair it with the valves that have the shallowest recession.
Make sure the lifters are on the base circle of the cam, and the piston is set to come up on what would be the compression stroke.
I assemble it with a clean, used, head gasket that I have, torquing the headstuds to 150ft lbs, (don’t forget to put the clay on top of the piston)! As it goes together adjust the pushrods until the valves are closed, and there is zero lash.
Then rotate the motor until both sets of valves have gone thru a complete open/close cycle, disassemble and measure the thickness of the clay.

 

[Jonnydime]

Disassemble the lifter, pull the internals out, and I cut a bolt to the correct length so that I could just get the cup and retainer back in. You’ll need two lifters done that way. Essentially make it a solid roller lifter.
Then you need a set of adjustable pushrods.
I then pick the cylinder with the most piston protrusion and try to pair it with the valves that have the shallowest recession.
Make sure the lifters are on the base circle of the cam, and the piston is set to come up on what would be the compression stroke.
I assemble it with a clean, used, head gasket that I have, torquing the headstuds to 150ft lbs, (don’t forget to put the clay on top of the piston)! As it goes together adjust the pushrods until the valves are closed, and there is zero lash.
Then rotate the motor until both sets of valves have gone thru a complete open/close cycle, disassemble and measure the thickness of the clay.

Can you put clay on top of a diesel piston? Flat valve surface, piston protrusion and the fact that the combustion chamber is part of the piston not the head.

 

[Zeb]

Can you put clay on top of a diesel piston? Flat valve surface, piston protrusion and the fact that the combustion chamber is part of the piston not the head.

I put a bead of clay around the deck of the piston. The valve “overhangs” into the bowl a bit, but will imprint the clay when you roll the motor over.
Have you ever seen a 6.0/6.4 piston with valve marks in it? If you have I think what I’m saying will make sense to you.
If I knew how to post pictures, I’d post a few of what I’m saying.

 

[Jonnydime]

Mine have valve reliefs so I don’t have to worry about contact. LOL

 

[DEEZUZ]

You can see here where the valve is

LOL

 

[powerstrokeboss]

I also have 50 thousandths valve releifs, I think I got about 37 thousandths of clearance between the valve and piston. The whole kit was from dynamic diesel

 

[Zeb]

I also have 50 thousandths valve releifs, I think I got about 37 thousandths of clearance between the valve and piston. The whole kit was from dynamic diesel

How did you go about checking clearance?

 

[Zeb]

You can see here where the valve is

LOL

For some reason I can’t see the picture. :shrug:

 

[DEEZUZ]

Hmm. Anyone else?

 

[79jasper]

Nope, fine here.

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[powerstrokeboss]

Not i