What was found
(CAN) DURING TAKE-OFF THE CREW HEARD A LOUD BANG FOLLOWED BY A DROP IN N1 FROM 80 PERCENT TO 19 PERCENT ON THE NR 1 ENGINE. AT 70 KNOTS FORWARD SPEED A REJECTED TAKE-OFF WAS INITIATED WITHOUT INCIDENT. ON RETURN TO THE GATE, OIL PRESSURE DROPPED TO ZERO. NR 1 ENGINE WAS REPLACED IAW TASK CARD 80UN-014 AND ENGINE RUN CARRIED OUT SERVICEABLE IAW TASK CARD 80EC-001AR1. AIRCRAFT WAS DISPATCHED AND NO FURTHER PROBLEM DURING SUBSEQUENT FLIGHT. ENGINE WILL BE SHIPPED TO THE O/H FACILITY FOR TEARDOWN AND REPORT ISSUED.