[FC] Bottom Shrouds

[ganderson8 at juno.com]

During the recent discussion regarding engine cooling and the advisability of removing lower engine shrouds, someone chimed in that they recalled reading somewhere that GM had tested engine cooling without shrouds.  I, too, recalled reading that but couldn’t find the book (oldtimer’s disease).  The lost has now been found.  
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The appropriate references are on pages 45 (text) and 47 (table of test results) of The Classic Corvair by Bob Helt.  Bob says, “The lower engine shrouds can be removed in the heat of summer for improved cooling.  Just remember to replace them for cooler weather.  When they are off, the heater will be essentially inoperative and engine warm up will take longer contributing to additional engine wear.  Chevrolet tests, Table 8-5, have shown that removal of the lower shrouds will lower oil temperature by 14 degrees and head temperature by 24 degrees at 60 MPH IN 100 degree ambient air.”  He goes on to discuss the merits (or lack thereof) of external oil coolers, water injection in the cooling fan, deflashing heads, paint, ceramic coatings, and electric fans.  
 
The table of Chevrolet test results includes separate outcomes from testing the effects of each of the following:  A.I.R. option, A/C using 1966 style condenser, switching to a 1960 24 vane fan, changing from an 8 plate oil cooler to 12 plate, adding oil cooler side shields on the 12 plate, adding louvers in the lower shrouds, and complete removal of the lower shrouds.  
 
I doubt that the columns of the table would align correctly when posted here, so I won’t try retyping the entire table.  I’ll summarize by saying that at a speed of 80 mph, going from an 8-plate to a 12-plate oil cooler resulted in a 16 degree change in oil temp (no results posted for head temps).  Side shields on the 12-plate reduced  oil temps a further 7 degrees and head temps 5 degrees.  At a speed of 60 mph, louvers in lower shrouds dropped oil temps by 7 degrees and head temps by 14 degrees.  These results were nearly the same for speeds of 80 mph.   At 60 mph, removal of the lower shrouds reduced oil temp by 14 degrees (18 degrees at 80 mph) and head temp by 24 degrees (28 degrees at 80 mph).
 
The table containing Chevrolet cooling test results notes that tests were run at ambient temperatures of 100-107 degrees in mid-1966.  
Gary Anderson
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