Short block

Short block is an automotive term describing an engine sub-assembly consisting of the following:

• cylinder block. The block is free of cracks and holes, the deck's flatness is within specification, the cylinder bores are finished to specification, and the crankshaft saddle alignment is within specification. Block cracks and holes can be repaired by pinning, the bore can be honed to the next oversize, and the crankshaft saddles can be line bored for straightness.
• crankshaft. The crankshaft is free of cracks, heat damage, deep ridges or scores, the crankshaft is not bent, and the taper and out-of-round of the journals are within specification. The crankshaft is installed in the cylinder block using new main bearings and thrust washers, and the main bearing caps are torqued to specification.
• cylinder liners. Liners are fitted to the cylinder block according to manufacturer's instructions. Liners are finished as necessary. Not all engines use replaceable cylinder liners.
• rods. The rods are not bent, twisted or cracked. They are installed on the crankshaft with new rod bearings, and the rod bearing caps are torqued to specification.
• pistons. Normally new pistons are used. If required, appropriate oversized pistons are used. New rings, piston pins, and piston pin bushings are fitted to the piston. The pistons are installed on the rods using and are placed in the cylinder block.

On overhead valve and flathead engines, the camshaft may also be installed. If the engine uses timing gears, they may be installed and timed.

On flathead engines, valves may be installed.

As an assembly, the short block requires no further machine work on the part of the buyer.

See also: Long block.