Were the factory BB fans 5 or 7 blade? Also, what was their diameter?

I just sold my 66 Chevelle 396 Big Block so I'm checked out in that dept. The original 396 came with a four bladed fan believe it or not with a Thermal Clutch that shut off the fan use during highway driving. Those worked great if you kept everything stone stock. I think they were 17 inches that fit into the stock plastic shroud. Hope that helps...

Bob in CT

Seven blades on a thermostatically controlled clutch 18" in diameter on pick-up trucks and big Chevy's (Impala B-bodies), five blades for the Small Block Chevy, same diameter.

There is also a fixed stainless steel flex fan from GM that was used for three years, that had six blades with a fixed hub 18" in diameter. My '77 is out in the barn, and it is currently raining or I would walk out to the barn to measure it. I think they are 18" also but without a tape I won't say for sure. (it isn't the rain but the lightning that keeps me out of the weather, and if you have ever experienced a Central Florida summer thunderstorm you know what I am talking about).

Big Dave

69-70 nova were 5 blade no clutch.

5 blade is correct for 69-70...both L-34 and L-78. 1968 used a 5 blade with clutch...but that year had the short water pump. There are many fans that will fit and probably cool better than the stock 5 blade....radiator core size and water pump style will dictate the room you have to work with. I use a 7 blade fixed steel fan on our 68 BB with 4 core rad...keeps everything nice and cool. There are some great aftermarket water pumps from Stewart that help improve cooling...they also offer a hi-po thermostat...hope that helps.


wilma