QUOTE(RolinkHaus @ Mar 17 2020, 06:16 AM)
Upon re-installing the engine, is the engine compartment seal necessary? Would it not create a little more air flow, leaving it off?
No. Don't leave the seals off. You don't want airflow though the seals.
The seals are there to help establish a separation between fan inlet (low pressure area) and the fan outlet above the cylinders (higer pressure area). This keeps cooling air moving in the proper direction.
You want segregation between the cool air above the engine (inlet) and the hot air exiting below the engine. That hot is is then drawn out from under the car by airflow under the car when it's moving and the seals separate it when the car is stopped and idling.
Hot air rises. At idle, without underbody airflow, and without engine compartment seals, the hot air will just rise up into the engine compartment and be recirculated. Worse yet, at idle it will actually be drawn upwards by the low pressure fan inlet and will be recirculated.
Without seals you'll get a mixing of hot air from under the vehicle being drawn back into the engine compartment. This will IMPAIR cooling.
Trust the Germans, they had this air cooling thing figured out.
Alternatively - don't leave out the thermostat and the cooling flaps either. Those are needed too. Removing them leads to slower engine warm up and hotter running temperatures. The flaps act to direct air over the engine mounted oil cooler which it looks like you are keeping.