i want to swich from a stock mechanical fan to an electric fan. it is on a fairly built 283. it has a 180* stat and NEVER gets above 180. the fan clutch isn't working right, it is about half engaged at all times. my question is what is a good cfm rating for an electric fan? should i get someting above 2000?

 

TheViper,

I've tried to research this one myself with little success. I wondered about cfm for a larger displacement engine (like 383). There are differing opinions out there. Hope this gets you in the ball-park
Perma-cool's guidelines are:
http://www.perma-cool.com/Catalog/Cat_page16.html
2000 cfm for 6 cyl. engines
3000 cfm for small cube eights, and
4500 cfm for larger cube eights
However, others contrast this with much more possible air flow requirements. Stewart's site (somewhere, can't find it right now) stated that at most 2800-3000 cfm is needed for most engines. This seems more in-line with convention. An article from CHP states about the same, "A high-performance V-8 typically needs about 2,800-2,900 cfm for adequate cooling."
http://www.chevyhiperformance.com/howto/81658/
BeCool's set-ups are also a good indicator.
BeCool sells its "modules" that include radiator and fan in a kit. One of their modules is a 700hp model that comes with dual 11" fans making a total of 2800cfm (I am going with a similar set up).
http://www.becool.com/
(Check out Module Introduction)
So, to make a long story...well, less long, I would think that with a 283, you could certainly go with less cfm. But it doesn't hurt to have more rather than less.

Ben

 

Just my .02, but I think since our cars are bottom breather you can throw "conventional" thinking right out the window. I have a real mild small block in my car that I tried with the original single factory electric fan set-up the 305 had-was not sufficent. Switched to an Iroc dual fan set-up, and even then it still gets pletny warm in the summer in stop and go traffic. Hopein with the things being done this winter it'll help a little in the temp department.

 

I have had no problems with the single factory fan used with the 305's. Just run to the auto parts store and get a new motor for it. Seimens Westinghouse makes a good motor. Also installing a lower temp thermostat helps. Hypertech makes one. Another thing I have found helpful is wiring in a fan override switch in the car. This lets you turn the fan on at any time, even when the car is turned off. I own an 84 TA with a far from stock motor and it cools, even in the hot summers of Florida in traffic.