So this happened while adjusting the rockers rocker colapsed while turning the engine by hand.
Any idea why, bad lifter possibly?
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How are you setting preload on the lifters? When you set the preload (adjust the rockers) on the lifter, you need to have that lobe for the corresponding pushrod/rocker arm on the base circle of the cam so the lifter is at the bottom of the lifter bore. By looking at the above photo it appears you ran the nut on the rocker arm down until the plunger in the lifter bottomed out in the bore. With that lifter in its current location in the pic, the plunger should only be down about .025-.030 or so if it is set correctly. By seeing the plunger so far down in the lifter I suspect you might not have set the lifter preloads correctly. I've never seen a hydraulic lifter so far collapsed unless it was broken at that point. Even if a lifter isn't "pumped up" it shouldn't be compressed so much. (Picture with both lifters and one is broken)
There is a whole sequence for setting lifter preload and everyone has a little variance on how they do it. Some people do each individual cylinder one at a time right down each bank, Some people follow the firing order, but no matter how you do it, it needs to be done correctly. I have never gone, and most people I know haven't gone more than a half turn past zero lash. Zero lash is when the pushrod stops having "play" to it. SO say if everything is correct, and you are adjusting the preload on the #1 cylinder. You start tightening the locknut on the rocker arm down, as you are you wiggle the pushrod up and down until there is no more up and down movement (this takes a little practice and patience to do) and when you get to that point you are at "zero lash", then you give your wrench or ratchet, or whatever you're using one half a turn more and you have the correct preload for a hydraulic lifter set. Some guys will spin the pushrod until they feel that initial "resistance" which is also the point of zero lash. Some guys, myself included kind of use a mix of the two when adjusting preload. And then you continue either through each cylinder or bank until you have them all done. If you have the intake off it will make it so much easier to see what i'm trying to explain when you're looking directly at the lifter as you set lash.
The cliffs notes version is, lifter all the way down in the bore on the base of that respective cam lobe, tighten the locknut while wiggling, spinning, rocking the pushrod until there's no more "free play" and then half a turn more with your locknut. And if the intake is off so you can watch while you do this, even better! Because what you're looking for if everything is correct, is the plunger inside the lifter to just start to compress down and away from the snap ring that keeps it in place. So if you've done the part of taking up the free play correctly, when you go that final half turn, you will see the plunger compress down enough to see a gap form between the plunger and the snap ring on the lifter, and your preload is correct. (Picture with snap ring double circled in red is where you will be watching.)
I would just hate for you to go through the trouble and expense of potentially breaking new parts you are going to install because you maybe didn't understand it well enough, there's a wealth of knowledge here and google sometimes will also be your friend.
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Edit: I went and found a link at Summit racing that might also help you.
https://help.summitracing.com/app/answers/detail/a_id/3318/kw/setting lifter preload
