The machining process of cutting the inside of an engine's cylinders to make them perfectly round and slightly larger. This is done during an engine rebuild to remove wear, scoring, or taper caused by the pistons. After reboring, the engine requires oversized pistons and piston rings to match the new cylinder diameter.
The cylinder walls were too scored to just hone, so we had to rebore the block thirty thousandths over.
Also heard as
- bore out
Related terms
Overbore
To machine an engine cylinder to a larger diameter than its factory specification.
Oversize
A piston or piston ring dimensioned larger than the factory specification to fit a rebored cylinder.
Short block
A partially assembled engine bottom end lacking the cylinder head and oil pan.
Piston slap
A knocking sound caused by a piston rocking sideways against the cylinder wall.