Bent push rod

They can interfere a small amount and this causes a resonance. If the conditions are just right it bends the factory pushrods. The factory ones are 11/32 in pushrods. The solution is to decrease the diameter of the pushrod slightly and run a heavier duty one. I sell the ones needed to fix the bending issue. They are a 5/16 .080 wall heavy duty pushrod. By using something like that it eliminates the interference and increases the strength. However one must consider in your situation the mileage. Some will experience the issue in under 10k miles. In those cases It was likely interfering from the factory. In your situation you have a decent amount of miles pre failure. This means it didn't interfere enough to cause a problem until recently. So considering that something in the engine has shifted. It could be a non-issue such as the valve seat and valve moving slightly or it could be a situation where your rocker arm bearings are wearing out. If it's something like the rocker arms you will want to do something to fix it. If it happens to be the valve seat and valve, unless you have a reason to pull the head again just leave it for now. Hopefully you had a valve job done so that's a non issue. Regardless, I wouldn't run the factory pushrods anymore.