440 head noise. Perpetual problems. Problem solved

You need to listen to experience. I have seen first hand a broken flex plate or loose torque converter bolt resonate completely through the engine and sound JUST like valve train noise. It costs nothing to get under the car and eliminate that possibility.

You can eliminate the cracked piston and or bad wrist pin or rod bearing by pulling plug wires one at a time while running. When you get to the offending cylinder, the noise will either diminish significantly, or vanish altogether.

This is very easy diagnosis......that is IF you listen to those of us who have done it over and over and over for decades.