At
any rate the reason I started this sub thread was to ask if anyone more
knowledgeable about engines than you or I knows the theory of the 8-6-4
engine and how it was supposed to improve gasoline mileage, which as I
remember it was what the hype said it was supposed to do?

Internal combustion efficiency is determined by the compression ratio.
High-vacuum conditions reduce the effective compression ratio. Going
to smaller displacement( through de-activating cylinders) meant
operation at higher manifold pressure, and thus higher
compression( from a given cam timing and combustion chamber geometry).

Unfortunately, you were dragging along other cylinders. There were a
few means of reducing the pumping losses, some worked better than
others. Also, the inactive cylinders were rotated in order to maintain
operating temperatures.

There's more to it, but those are the broad strokes.
cheers,
Douglas