[unruhjonny]

Long story short, when assessing the "running" numbers correct engine that I got for my car several years ago, I made a starting discovery that made me scratch my head - and in my mind required me to pull the #12's, in favor for aminty set of '68-350 heads that I had handy;

Several of the pushrods were damaged, as were several of the rockers (pictured below), and several of the valve stem tops had appeared to 'shear' off above the keepers...

My question is;

How in the world would some one do this?

[TransAm525]

My first guess would be valve spring coil bind. Once the spring is fully compressed, something has to give. In your case, it appears the problem went unnoticed long enough to damage everything. If this is the case, the cam and lifters are probably damaged just as badly. Hopefully you can account for all the small broken rocker arm pieces. If not, at a minimum, pull the oil pan and check there.

[steve25]

spring bind, or the rockers and balls got mixed up,and or the rockers had bad worn spots and the added lift of a new cam was jamming the rocker(s) from moving.
Spring bind to me should have happened to all the valves, or just the 8 with the highest lift as on a duel pattern duel lift cam.

[fiedlerh]

in addition to the above comments, it can be from floating the valves since you're hammering the parts together on the rebound. Some crappy aftermarket rocker arms from the old days may have been manufactured incorrectly making them fracture-prone in that area, but since the valve ends were hammered, I lean towards over-revving.

[lust4speed]

I've had this problem on a mild build that shouldn't have placed very much load on the valve train. Stock pushrods don't like to be reused, and they will start to flake from the center hole outwards. Once enough of the pushrod is eaten away, the end acts like a hole saw on the rocker. I immediately toss the stock pushrods when I take an engine apart to avoid the temptation later on to cheap out without replacing them.

Take a good look at the other pushrods you think are okay, and I bet you will see the center hole somewhat eaten away.

[unruhjonny]

Thanks for the tip Mick!

I have reused pushrods time and again, and NEVER heard of this...

[TransAm525]

Originally Posted by unruhjonny

Thanks for the tip Mick!

I have reused pushrods time and again, and NEVER heard of this...

I agree. While it is possible, I don't think such is the case with this failure. If you look at the two rocker arms at the top of the photo, the pushrod cups appear to have normal wear patterns. The fact the valve locks were sheared off highly suggests coil bind. Once the spring is fully compressed, any additional lift thereafter will simply try to force the valve and locks right through the retainer. Why this only happened with a couple valves is a mystery. Could be mix-matched valvetrain parts, improperly machined spring seats, etc. Additionally, maybe it's some sort of stain, but the two rockers at the top of the photo appear to have some blueing around the pivot points, leading me to believe they may have been under extreme pressure, thus building considerable heat.

[lust4speed]

Good catch on the bluing. When I read about the tops of the valve stem shearing off, I didn't relate this to the locks shearing. If they did, then that changes things. I actually interpreted the tops coming off to simply mis-identifying lash caps, but I could be wrong.

[unruhjonny]

what ever the case, it's plain crazy!?