Help Me with a Diagnosis

Hi. My name is Stacey. I have 4 Z cars at this moment. My '75 280 has a problem & I can't figure out what the problem is. Can you? #1- A "popping" sound" like a compression sound" in the #4 cylinder when the plugs are removed and #2- A "knock" also out of the #4 cylinder that corresponds with the intake valve cam load after it closes. The compression is equal to the other valves-160. And last but not least how do I look for damage in the spring rocker arm & pivot? If anyone could help me. Contact me ASAP.