Is this an engine that has been sitting and hasn't run for a long time? If so could it be a valve guide or broken spring problem?
Laquer thinner dribbled down the stem will dissolve varnish residue from old gas that often is on the stem. Once free follow with a soaking of Aero Kroil and finally a few drops of diesel. I've had over half of the valves stuck before and if quiet in the shop one could hear the snap as they became free. The newer and better shape an engines in when left set up the worse the valve sticking is. Old worn sloppy ones usually don't stick.
Thanks for the response. The truck has been sitting for 10 years. The springs look good but there were two bent push rods. This was after the engine had been running a couple of times.
Sticky Valves What Evan said ! just remove the sparkplugs and use a hand pump oiler to squirt in the Kroil (or ATF) between the valve spring's coils to wet the valve stem as you hand turn the engine ~ after a few times of up and down they'll usually free up O.K. . I hope you know to NEVER straighten and re-use a bent pushrod ! . it'll wait uintil the worst possible moment before suddenly fsailing again .
