trying to find out what caused the valve to be bent. i can see where it hit the piston, not bad damage, but it's scraped up. is the 4.3 vortec non-interference? rocker looks o/k, spring looks good, pushrod also looks good. timing chain did NOT skip a tooth, but there is alot of slack. this is my sons truck, so not sure what exactly happened when it bent. he was driving to work and check engine light started flasing and running really crappy. pulled over and we towed it home (some coolant spilled out when he pulled over). sounded like the exhaust was clogged,running very rough. seemed to be running worse than just 1 bad cylinder. unbolted cat and still was the same. checked compression, all were good except the one cylinder , 0 (zero) compression. rear cylinder passenger side. want to put used head on , hope for the best. can lifters expand to open valve too much ? any help would be appreciated. jerry
vehicle has 140k miles, regular oil changes
also, the spring that goes around the stem seal on tht cylinder popped out when i removed the keepers. the spring is crushed in 4 places . don't know what crushed it, maybe it popped off the seal and wedged between seal and valve stem ?