HT 4100 OIL LEAKAGE AT CYLINDER HEAD BOLTS

SOME HT4100 ENGINE BLOCKS MAY EXHIBIT CASTING POROSITY EVIDENCED BY OIL LEAKAGE AROUND THE THREADS OF CYLINDER HEAD BOLTS. THIS LEAKAGE IS CAUSED BY POROSITY BETWEEN A PRESSURIZED OIL PASSAGE AND THE THREADED BOLT HOLE, AND OCCURS PREDOMINANTLY ON THE RIGHT BANK OF CYLINDERS. WHEN THIS POROSITY OCCURS BETWEEN AN OIL GALLERY AND HOLES #11, 12, 13, 14, 17, 18, 19 OR20 (REFER TO FIGURE 1), AN INTERNAL OIL LEAK WILL OCCUR WHICH IS OF NO CONSEQUENCE AND WILL RARELY BE DETECTED. HOWEVER, WHEN THIS CONDITION IS EXPERIENCED AT BOLT HOLES #1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15 OR 16 (REFER TO FIGURE 1), AN EXTERNAL OIL LEAK MAY RESULT. TO PROVIDE A PERMANENT REPAIR FOR THIS CONDITION, PROCEED AS FOLLOWS: 1.REMOVE THE BOLT AND CLEAN BOTH THE BOLT AND THE HOLE WITH GM FABRIC CLEANER, P/N 1050244. 2.BLOW OUT THE BOLT HOLE WITH COMPRESSED AIR. 3.OBTAIN A FAST CURE (5-10 MINUTES), TWO-PART EPOXY AND APPLY THE MIXTURE TO THE LOWER 5 OR 6 THREADS OF THE BOLT. (ANY FAST CURE EPOXY SHOULD BE SUITABLE.) 4.INSTALL THE HEAD BOLT AND TORQUE TO 120 N.M (90 FT. LBS.). FOR WARRANTY PURPOSES, USE LABOR OPERATION NO. T6053 FOR UPER BOLTS AND T6054 FOR LOWER BOLTS WITH TIME ALLOWANCES AS FOLLOWS: UPPER BOLT: RIGHT (HOLES #11, 12, 13, 14 OR 15) - 1.4 HOURS LEFT (HOLES #16, 17, 18, 19 OR 20) - 1.0 HOUR LOWER BOLT: ANY ONE (HOLES #1, 2, 3, 4, 5, 6, 7, 8, 9 OR 10) - .2 HOUR

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