[Formulabruce]

When I was sent to GM schooling on Cooling, brakes, exhaust, carburation for ASE cert. I saw and learned a lot that I thought I knew.
( Being young and stubborn and knowing it all based strictly on common sense)
Cooling, I learned how and why the fan shroud was made and what it does. I wish I could have the giant poster on the wall there of engineers
standing around a car ( 1960 Pontiac I believe) and some with clip boards, and others reading all of like 30 different Vacuum gauges they had
on nipples around the fan shroud.
What I was taught was that keeping the fan blades furthest point, or edges closest to the shroud IS most efficient.
In most cases the fan is just barely inside the shroud.
That said they said the cooling was a total package based on the weight of the car, and the CR of the engine.
Cooling "systems" were designed to handle up to 18% excess heat produced for desert use.
So, its totally possible that "most" GM cars produced that run on original, or equivalent fuel ( lead additive ) and no alcohol
will run fine with some fluctuation in the fan distance in the shroud.
Low CR or lower rpm engines dont need a fan shroud, like a cheby inline six, or a 2bbl 327 .
Get into 4bbl, and add on AC and a lot can change in the cooling system
If anyone doubts the fact that this system uses the LEAST Horsepower, and does the BEST job, look no further
that Hot rod TV. The engine masters had all sorts of cooling set ups at a Dyno, and made their bets..
They all lost. I find it amazing how many people think that the factory engineers didnt know what they were doing.
Air doesnt do sharp corners....The same folks that want their heads all smoothed and ported will run a hideous restrictive cooling system
because its in a catalog... ... Some things ( not all) are best left stock...