Ok I bought a 98 150 with a blown 4.2. When I tore into it I found out that it Hydro locked with a blown intake gasket. It snaped the #1 piston rod and bent the #2. The #1 piston was almost at TDC when it snapped and the valves were slapping the top of the piston. So I bored it and completely overhauled it. When I was putting it all back together I didnt get new push rods I just rolled them on a flat table to check for bends. I didnt see anything so I put the old ones back in. When I first started the motor for the first time everything sounded fine but today when I started it there was a slight tapping sound under the valve cover. Same side as the snaped piston. Im wondering if I didnt bend or put in an already bent push rod. I have never heard what a bent push rod sounds like and I was wondering if anyone has had any of the same problems or has some suggestions on what it might be. Before I tear into it again. Thanks for all the help!

 

It could just be a loose rocker.Did you torque them down to 29 ft. lbs?
BTW,when I use to rebuild engines and went back with used push rods,i'de roll them on a piece of glass or mirror.