Its not just the displacing of the pistons air, it is any pressure in the crankcase including pressure that leaks passed the rings. On a car(8cyl race engine) running an air pump in reverse to keep a negative crankcase pressure hp increases of 20-30 hp are not unlikely even with the pump being belt driven so there is power to be had. the rings will seal better and you can get away with a lower tension ring set therefore freeing up more hp. This setup however I dont believe will create the amount of vacuum needed to make it effective.(I ran the crankcase on my car at 12" vacuum) On the motorcycle powered sprint cars the valve covers are modified to block off the runners to the exhaust and holes are drilled to allow crankcase pressure to escape the top port on the plate, we run breathers on each plate to keep dirt out. If there was a way to gain more power the circle track guys would have found it and all the engine builders are doing it by venting it with breathers.
Thanks for your input.
"Volume" is the key for big gains. I will be doing further research for the 10. Although the gains are not going to match those of the aftermarket vacuum pumps, the idea is to use what we already have in place to our advantage. Even if the HP gains are nothing, the reduced work/resistance in the case should net a faster revving engine at least. IMO