As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT 4000 FT AND 250 KTS AT APPROXIMATELY 75% NI WE HEARD A BANG FROM THE REAR OF THE AIRCRAFT .ADDITIONALLY THE LEFT ENG VIBRATION GAGE INDICATION SIGNIFICANTLY HIGHER THAN THE RIGHT ENG. AFTER LANDING WE NOTED EXCESSIVE OIL ON THE LEFT WING. INSTALLED (1) 2.5 AND (2) 2.8 BLEED VALVES AS A PRECAUTIONARY MEASURE FROM A SUSPECTED COMPESSOR STALL. ALL WORK DONE I.A.W P & W 306A M/M CH 75-30-01. COMPLETED SATISFACTORY BOV OPS CHECK. WORK DONE I.A.W. PW306A M/M CH 71-00-00.