What was found
(CAN) DURING TAXI OUT TO RUNWAY CREW NOTICED AN ODOR WHICH ALSO SET OFF THE LAVATORY SMOKE DETECTOR. AIRCRAFT RETURNED TO GATE. TROUBLESHOOTING BY MAINTENANCE REVEALED SMOKE WAS ENTERING INTO CABIN WHEN BLEED AIR SELECTED ON, NR 1 ENGINE. ENGINE WAS REPLACED. ENGINEERING REPORT BY FROM ENGINE TEARDOWN INDICATED THAT THE OIL PRESSURE SUPPLY TUBE FOR THE NR 5 BEARING AREA WAS CRACKED AT A WELD SEAM IN THE GASGENERATOR CASE. ENGINE WAS REPAIRED. REPORT AVAILABLE IF REQUIRED.