I've had a valve stick from a leaky header. Pulled the head. The valve hit the piston. Piston was fine. Replaced the valve and all was good.

I dont think the guide is exposed to the water jacket like it is on a GM iron head, which i believe its only the exhaust valve that the guide is exposed to the water jacket.

Sounds to me like maybe something went wrong with the spring replacement. Like, rocker nut wasnt tightened properly, spring coil binded, keeper wasnt in properly, etc .

Of course most mechanics arent going to tell you they messed up and have to eat the repair bill. Easier to say it stuck a valve from a header leak.

If the valve tagged the piston, then there isn't much doubt in my mind that it's stuck in the guide. That is more than likely an effect, not the cause. As Mild said, something probably went wrong with the spring replacement (which happens very easily when changing springs with the heads on) and the valve hit the piston, causing it to bend and hang in the guide.
Eddie

The last motor I tore down had a stuck exhaust valve kiss the piston. Exhaust manifold had a leak which corroded the valve stem and guide. Leaky exhaust can be one cause.

Alright another valve issue. Here are the pictures. The one with the twisted rocker is the first time along with the piston that got tapped. Other pictures are the most recent failure. Running 3800. Motor just shut right down. Head of valve sheared off. Destroyed the piston and head. Cylinder wall is all bear up. Picture of the whole head with all the other valves still in. One bank of plugs were white as can be. Any idea what is going on? <iframe width="480" height="360" src="http://s1381.photobucket.com/user/kevin_joseph2/embed/slideshow/Mobile%20Uploads"></iframe>

Is that the same cylinder with 2different failures?

No first failure was cylinder 7. Second failure was #8

How many hours on those rockers?

that I don't know. The first valve that stuck we pulled the oil pan and a rod bearing and checked out the cylinders. the motor looks to be basically brand new. It def is a rebuilt motor though I know that

Anyone know what brand the stock valves are?