BRDM-2 suspected failed valve seal 

We suspect that a valve seal has failed on the GAZ-41B engine in our BRDM-2. This means that oil is being drawn into the cylinder from the rocker cover through cracks in the seal. Also note the engine tapping noise from the same engine side which is present on the opposite side, (I should add that we checked that the valves aren't cracked with an endoscope). These clips were taken after warming the engine up to 60°C over 25 minutes. Any feedback on your thoughts to the problem would be appreciated.