subtracting solid volumes from a model

Hello Everyone.

i have been lately trying to subtract the solid volume from car engine model . however, i still need to keep some solid parts in the resulting solid volume.

and i am using joining features along with intersection feature to subtract the solid volume and i managed successfully to get the solid volume but i couldn't manage to keep some solid parts that i need to keep in the solid volume.

can anyone help or suggest a way for doing that ?

thank you for your time

SolidworksParts And Features