Block Inspection

INSPECT FOR CRACKS
After the cylinder block has been thoroughly cleaned check it for cracks. Inspect the cylinder block for cracks in the cylinder bores and between cylinders. Also look for cracks at the water pump opening and in the main bearing web area. If cracks are suspected that cannot be seen with the eye, there are magnetic and dye check inspection processes available through automotive machine shops. Be sure the water jacket engine block plug opening is clean and not damaged. Tiny cracks not visible to the naked eye may be detected by coating the suspected area with a mixture of 25 percent kerosene and 75 percent light engine oil. Wipe the part dry and immediately apply a coating of zinc oxide dissolved in wood alcohol. Do not use rubbing alcohol as a substitute. If cracks are present, the coating will become discolored at the damaged area. Replace the cylinder block if it is cracked.

CHECK BEARING ALIGNMENT
If difficulty is encountered in rotating the crankshaft when fitting new crankshaft main bearings (6333), or an unusual wear pattern is noticed on the crankshaft main bearings, the problem may be a distortion in the crankshaft main bearing bore alignment. This can only be corrected by line-boring or by replacing the cylinder block.

CYLINDER BLOCK DISTORTION
Testing
The cylinder block cylinder head surface must be flat within 0.15 mm (0.006 inch) over the entire surface. Use Straight Edge D83L-4201-A or equivalent and a feeler gauge to determine the flatness.

Repairing
If the flatness is out of specification, the head gasket surface can be machined a maximum of 0.254 mm (0.010 inch). If the cylinder block distortion exceeds the maximum of 0.254 mm (0.010 inch), the cylinder block must be replaced.

CYLINDER BORES
Also, inspect the cylinder bores for wear. They must be round, straight (sides parallel), and the diameter matched to the piston size.