Question: 5 blade or 7 blade fan

[paul robb]

Does anyone know witch fan actually pulls the most cfm's ? Some say the five blade fan will pull more cfm's than a seven blade fan.
The different corvette sites show the fans but have no other information. I would like to find the fan that pulls the most cfm living
here in Arizona. Any help would be greatly appreciated. This is for a 66 vette with a 327/300

 

[JohnZ]

Does anyone know witch fan actually pulls the most cfm's ? Some say the five blade fan will pull more cfm's than a seven blade fan.
The different corvette sites show the fans but have no other information. I would like to find the fan that pulls the most cfm living
here in Arizona. Any help would be greatly appreciated. This is for a 66 vette with a 327/300

Fan CFM is more a function of blade pitch than number of blades. The best '66-'67 fan is #3789562 - 5 blades, 18" diameter, 32* pitch, "H" and "W" stamped on the mounting ring center, arrowhead-shaped arms with four rivets. Identical alternative is #3863137 - "912239" and date code stamped on blades, rectangular arms, 5 rivets, 32* pitch. Both were used interchangeably on '66-'67 327's with A/C.

7-blade fans weren't used on '66-'67's, either small-blocks or big-blocks; non-A/C fans had less blade pitch (24*).

 

[paul robb]

Fan CFM is more a function of blade pitch than number of blades. The best '66-'67 fan is #3789562 - 5 blades, 18" diameter, 32* pitch, "H" and "W" stamped on the mounting ring center, arrowhead-shaped arms with four rivets. Identical alternative is #3863137 - "912239" and date code stamped on blades, rectangular arms, 5 rivets, 32* pitch. Both were used interchangeably on '66-'67 327's with A/C.

7-blade fans weren't used on '66-'67's, either small-blocks or big-blocks; non-A/C fans had less blade pitch (24*).

Thanks for the quick answer John, One more question, what is the difference between the air condition fan
and the non- air condition fan ? I see one 5 blade fan advertised at 34.5 pitch. My vette is not a numbers
matching car and what I'm looking for is maximum cooling in summer with the air on. Thanks once again... Paul

 

[JohnZ]

Thanks for the quick answer John, One more question, what is the difference between the air condition fan
and the non- air condition fan ? I see one 5 blade fan advertised at 34.5 pitch. My vette is not a numbers
matching car and what I'm looking for is maximum cooling in summer with the air on. Thanks once again... Paul

The base (non-A/C) fan was #3770529 - 5 blades, 17-1/8" diameter, "H" on front of spider, "W" on back, 24* pitch, arrowhead arms, 5 rivets. This fan was used on all '63-'67 non-A/C 327 engines. Long Island Corvette Supply now has accurate reproductions of all midyear fans.