My 429 started making a ticking sound, then started running poorly. I assumed one of the roller rocker arms was out of adjustment. When I removed the valve covers, I found that the #2 cylinder exhaust valve was not opening all the way. I took off the rocker arm, and pulled the push rod. The push rod looked fine, as did the rocker arm. When I replaced the push rod, I pushed down on it to see how the seat felt. It felt springy. I could push down a good 1/4" or more, before it hit a hard surface. I then did the same with two others, to see the difference. Both of those felt solid, immediately. Could I have a bad lifter?