Flex fans

Ok, we resolved an air lock situation with MUCHO great results on the temperature -- have a shroud on the way (thanks to Craig Selvey) . Curious though, what's the difference between a 5-blade or 7-blade flex fan? Did a search in the archives until our heads hurt. Currently running with a 5-blade flex, though have a 7-blade at hand. Basically wondering why the 2 were offered (per our manual, 75-76), and what's different.

Rocky & Holly
Ocala, FL

 

Cars with A/C had a different fan, than cars without.

 

I'm glad yall got that fixed. :bananaman

 

First hand, thanks Jeff for the kudos, tho we're still working out issues... much, much better running down the road temp-wise, with the new 3-core, have proper shroud on the way, still heats up at lights.

Clarification on the question -- Ford 5-blade flex vs. Ford 7-blade flex -- which one pulls more air? Noticed on 5-blade Ford flex fan, blades are wider than the 7-blade Ford flex fan.

Thanks for the input and support.

Rocky & Holly
Ocala, FL

 

I hated my broken, cracked shroud and removed it.

My car overheats when it isn't moving...

 

The more blades, the more power it will use to turn. It all depends upon the pitch of the blades, as to how much air it will move.
My 74, 302 without A/C, just had a 4 blade (I think, it's in a box) fan on it from the factory, my 73, 302 with A/C has a 6 blade flex fan from the factory. The 6 blade fan must move more air, considering that the A/C car would have the condenser in front of the rad, so it would have to pull more, to go through both....

 

What temp when not moving? We've upgraded recently to normal 180-185 driving, to 190+ at lights...such a nice change from 215+ at times sitting.

 

My 73 usually runs around, 180-190, the highest it's been is close to 200 in heavy traffic on a hot day, high 80's. Even at the Round Up after coming off the highway, it might have gone as high as 210, but came right down again.
I had the rad redone, with the tighter cores, so there are more cores per inch compared to a stock rad. and everything else is new.
I know that the shroud is a very important piece in the puzzle, it needs it, to direct the air flow.

 

Clarification please, Ford shop manuals (75-76) specify 7 blade or 5 blade flex fans, which ones pull air better? That's all I want to know.

 

It all depends upon the fan itself, without seeing both it's hard to say.

 

Mine runs a 7 blade, no shroud(havent found one yet to fit) hasnt gone over 200 with factory rad.

 

Depending on the pitch of the fan blades the 7 blade may pull more than the 5 blade.All things being equal pitch wise,I would use the 5 blade with a shroud and the 7 without.Reason being...the 7 blade will create a larger resistance to incoming air flow at higher speeds than the 5 blade by virtue of its size and how it will fill the opening in the shroud.(more mass = more resistance)

 

the 7 blade is the way to go

 

Huh, I just recounted mine, it is a 7..took 3 beers ..but it's a seven. My service manuals just list the flex fans, they don't say anything about which moves more..

 

x2.......