Help! Swapped 302 heads on my 318.

We are all learning, that's what fabo is here for. I'm trying to throw questions out there that may lead to a solution.
IF a valve is hanging open....wrong pushrods?? Valve guides too small(grabbing the valve?? Coil bind as mentioned?? Valve height too tall?
You say heads rebuilt....pretty broad statement....new valves/guides/springs? Or were they transferred over from previous heads?
I'm hoping to learn from this as well.
What do you mean height change? Sorry im still learning. I got the 302 casting heads from a junk yard years ago. Just had them rebuilt at a machine shop that i e been using for years. When i called they said they checked the springs and the were good. But. Im going to check for coil binding on friday. I will measure the springs on the ild heads to see if they are a little taller. How do you measure lifter preload? Sorry Like i said im still learning