It's kinda like the "choofer" I have for my 4 wheel drive truck.
It is intended to be used as a tire pump that screws into one of the engines spark plug holes. A very handy thing to have after you've deflated your tires to drive over long distances of very sandy areas and want to re-inflate them for highway use.
Anyway, it has one way rubber flapper valves on it so when the engines piston is going down on the intake stroke, outside air rushes in thru the flappers.
No fuel/air mixture is sucked into the cylinder because there is a high vacuum in the intake manifold that is also trying to suck air into the cylinder when the intake valve is open.
Another valve between the choofer and the tire closes to keep the air from being sucked out of the tire.
When the piston is on the compression stroke, the air pressure closes the flapper valves and is pushed past the one way valve into the tire.
On a V-8, there are enough cylinders still operating that the engine idles quite nicely but that choofer makes one hell of a racket while its operating.