Cylinder Head Assembly: Service and Repair

Fig. 4 Cylinder head bolt hole locations. V8-250:

Fig. 5 Cylinder head bolt tightening sequence. V8-250:

V8-250
Some V8-250 engine blocks may exhibit casting porosity, indicated 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. This condition occurs between an oil gallery and holes # 11, 12, 13, 14, 17, 18, 19 or 20, Fig. 4. An internal oil leak will occur around these bolts 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, Fig. 4, an external oil leak may result. To provide a permanent repair for this condition, remove the bolt and clean both the bolt and hole with a suitable cleaner. With compressed air, blow out the bolt hole and apply a suitable two-part epoxy to the lower 5 or 6 threads of the bolt. Install the bolt and torque to 90 ft. lbs.
1. Remove valve covers, then remove intake manifold as described under ``Intake Manifold, Replace.''
2. On right hand side cylinder head removal, remove alternator and AIR pump.
3. For left hand side cylinder head removal, remove vacuum pump and bracket. Remove bolts and position power steering pump aside.
4. Remove exhaust manifold from cylinder head, then bolt securing AIR pipe to cylinder head.
5. Remove cylinder head bolts, then remove cylinder head.
6. Reverse procedure to install. Refer to Fig. 5 for cylinder head bolt tightening sequence.