<VV> Replace "cold" air duct to heater or block the port?

[Charlie]

Does the upper 3" duct from the engine top cover push "cold" air to the
heater

Is this just "cold" relative to the warm air that comes from left and right
lower 4" ducts off the exhaust?

 

Would that cold air do more good cooling the engine?

On the forum, it is reported that this upper duct from the engine top cover
steals cooling air from the #5 cylinder causing valve (guide) problems?

 

My own 3" duct was torn out and port has been blocked off ~ I was going to
spend $$ on a new 3" duct hose, but it seems to be a waste of $$ especially
if this would do more harm than good to replace it?

 

What purpose was this "cold air" duct intended to serve, and should I just
block the hole in the "firewall" too?

 

Charlie