Strange Noise/Strange Find
Missed a shift at the track last week and since then the engine has a misfire at speeds over 5500 RPM. Over last couple days, engine has developed a very strange, low pitched metallic clicking/thud sound in cadence with a single cylinder. Very strange sound, and removal/exam of the plugs didn't tell me anything. So, I removed the driver side valve cover and found the #7 intake pushrod had dislodged from it's rocker arm. The pushrod is not bent, and shows absolutely no damage to both ball ends. The rocker shows no damage, either. The underside of the aluminum cover shows a shallow concave spot, less than 1/4" dia where the pushrod was floating up and contacting it. The stud nut and lock were loose on the stud!
First, was it a coincidence that the noise and dislodging started right after the missed shift? Does it happen, from time to time, that the lock and nut can loosen and back off, causing the condition that I experienced?