Wow, I'm floored you guys can get a reciprocating noise out of that. Not doubting you a bit but I can hear intake air and exhaust exchanging there, so can Carl. This poor guy is going away with nothing more than he came in with, a big roll of the dice unknown. Listen to the end of the mpeg and you will hear the noise go away at an idle, I stand fast with a stuck valve or valves. Take the cheap way out on the further diagnosis before tearing it down, remove the valve cover and observe the valve action.

Last edited by sstock; 10/07/2019 7:04 PM.
1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration