Mopar viscous 5 blade or the Mopar 216 7 blade thoughts on what cools better

The mopar kit was put together for, supposedly, max cooling with minimal drag. It may also have been based on "the tooling we still have laying around."

The science of cooling is just that, science. It is actually possible to over cool an engine, which is why a three row radiator does not always out cool a two row - you are actually exchanging heat back into the unit at a certain point. This gets into delta t principle and I am sure there is a multitude of studies on the web if you have a few decades to kill.

In terms of a 5 vs 7 blade fan, issues like a well-fitting shroud, proper fan spacing within the shroud opening, properly functioning radiator, and an adequate water pump with the proper pulley spinning at the intended speed will make a much bigger difference than blade count.

My guess is that the 7 blade fan would show a nominal improvement over the 5 blade. You'd have to measure the surface area and pitch of the blades to figure that out. And then balance that against the added weight of the 2 extra blades to see if there is any real advantage. There are also 15" 5 blade fans, and 18" 5 blade fans.

Sounds like a question for Mopar Action. To the best of my knowledge Rick has never published a full blown write up on OE fans, there are a few mentions of factory clutch fans in the early 90s issues that I will have to thumb through now.

That seems to be a reasonable guess.
The MP 5-blade has more pitch than the ...215 18" 7 blade.
The blade is wider, approx 3.8" vs. 4.6"

Presumably the 18.5" ..216 potentially can move a little bit more air than the 18" 215. That can only occur if the surface area of the core is exposed to the fan's airflow.

IMO the big advantages to the early fans is the extra clearance with the round top radiators.

That also seems to be a reasonable guess. It would have been a lot harder getting a pre-70 style fan back into production than using something more current at the time.

I would get the 7 blade fan & the other things mentioned: proper fan spacing in a tight fitting schroud/correct overdriven pulley ratio/high flow stat (not less than 180)/anti cav plate in the pump/adequate radiator/several drops of dawn liquid dish soap for a water wetter/some antifreeze/air directed thru not around radiator/MP clutch fan. ballpark timing & A/F ratio. EDIT coiled spring in lower hose. good regular Prestone green antifreeze changed somewhat regularly.