One valve is sticking down and then pops up when the pistons hits and its making the rocker fall off caus its sticking down what will make just one valve stick down like that? was wanting to put motor in car but now i think i need a new head what will cause one valve to stick

 

It could be bent.

 

Guessing if the valve has been using the piston to close it, 99.999% chance its bent. . .

 

I have a head if you need one for an LS.