Line boring is used to correct misalignment of which engine component?

• A. Camshaft bore
• B. Main bearing bore
• C. Crankshaft journal
• D. Piston bore

Answer: (B)

Line boring is used to reestablish a straight, coaxial set of main bearing bores in the engine block. The main bearing bores provide the centerline for the crankshaft journals; if the block or caps are out of alignment, the crankshaft can sit off-axis, causing uneven bearing wear and binding. By line boring, a precise boring operation is performed across all main bores in one setup to bring them back into true alignment, ensuring proper crankshaft rotation and bearing clearance. This process is not used for correcting the camshaft bore, the piston/cylinder bore, or the crankshaft journals themselves.