From a previous discussion, this was said to be the stock fan specs:

Dimension: 120*120*38mm
Voltage: 12V
Start voltage: ≧8V (Power ON/OFF)
Power consumption: 1600RPM 1.68W / 4000RPM 25.8W
Rated current: DutyCycle 100% @ 2.15A
Air Flow: 4000RPM @ 178.3CFM (Max be 239CFM)
Noise: 4000RPM @ 56.7 dB-A (Measured in a Non-EchoChamber)
Life Expectancy: 40,000 hrs @ 25℃  (May degrade faster at higher temperature)
Connector: 2510-4P

Also, I recently tried a dual 60CFM fan setup (one for push, one for pull), but it was clearly not powerful enough - temps were at 70C within a few minutes. This is what I used:

http://www.newegg.com/Product/Product.aspx?Item=N82E16835553008

I just ordered the following Delta and am hoping I can use it alone for just push:

Delta Electronics AFB1212SHE 120x120x38mm Cooling Fan, 151.85 CFM, 58 dBA, 3700 RPM, 1.06 AMP, PWM 4-pin connector.

I have the miners running in a temp controlled room with proper ventilation, which helps the temp's, but I'm still worried if the Delta might not be enough as 2x 60CFM was clearly not even close.