I am not sure if we are all playing a game of oneupsmanship on 'To Tell a Story' or what, but I'm gonna ask this as if we are being serious in our storytelling.
Therefore, EXACTLY WHAT did the Marvel Mystery Oil do to "exploding valves" (-whatever that sounds like??

) to make the exploding sound go away? Since the Model-A engine uses a mechanical tappet, it generally is excessive lash clearances that causes a valve noise. From my vantage point, it is more likely that a higher viscosity oil would cushion the impact of the tappet hitting the valve stem, ...yet I would think that MMO being a
thinner viscosity, it would not help in abating that valve noise. If that was not it, then what other scenario would cause the valves to explode??