No. But you could. Otherwise leave plug in. It doesn't matter since the air will pressurize the case just about anywhere you hook it up. You just have to temporarily seal off all the normal oil/vent flow points. Just use the engine hoses that go to frame on the motor and use thier free ends to block off any open holes. I usually put the air to the oil inlet at back of motor because that is one hose I leave on frame when engine is removed. Kdeal has a engine plug kit that also works nice for this. It's just all the plastic plugs to seal off the motor so no dirt or insects get in there before install.