If some head-bolt holes in the block are filled with oil during head installation and torqued, what is most likely to occur?

• A. The head gasket seals better
• B. Oil will leak into the coolant
• C. The torque will be incorrect
• D. The cylinder block could be damaged

Answer: (D)

Oil in the head-bolt holes changes how the bolts clamp the head to the block. Torque numbers assume a certain friction on the threads; oil lowers that friction, so for the same torque the bolts can stretch more or seat unevenly. That misapplied clamping load can warp, distort, or crack the block around the head bolts. In other words, the most likely outcome is damage to the cylinder block due to improper or excessive clamping force.