350 valve train prolems

i have a mildly built 350. the problem is that it backfires through the exhaust. i took off the valve covers and all the valves seem to be working fine, except 1. it barely moves at all. could this be because of a bad cam, bent pushrod or something else? im tryin to get information before i start ripping into it to find the problem. thanks and any suggestions would help.

yes the backfire is caused by the valve not opening up all the way ..... i would pull the rocker arm off on the valve and then pull the push rod out and see if it is bent ...... if not you prolly had a lobe go down on the cam.....