These are great Antminer S3 and Antminer S4 replacement fans:

Delta ABF1212LE   2000-RPM  71-CFM  1.7-Watts  .14-Amps
Delta ABF1212ME  2500-RPB   92-CFM  3.2-Watts  .27-Amps
Delta ABF1212HE  3000-RPM 102-CFM  4.2-Watts  .35-Amps
Delta ABF1212HHE 3500-RPM 130-CFM 6.2-Watts  .51-Amps
Delta ABF1212VHE 4000-RPM 148-CFM 8.2-Watts  .68-Amps

The original specs call for 120mm x 38mm, 8 volt, (27.6/4)=6.9-Watts, with 238-CFM, and 4300(+-)10% RPM.  

I used the AFB1212HE for quieter and better power efficiency.  
Both front fans had come loose and would rub the stopping the fan causing the hashing to quit.