The rotating assembly located in the lower portion of an engine block, consisting primarily of the crankshaft, connecting rods, pistons, and oil pan. When mechanics discuss rebuilding this section, they are usually addressing bearing wear, rod knock, or upgrading components to handle higher horsepower.
Heard on the job
The top end is perfectly fine, but the bottom-end has a severe rod knock and needs a full rebuild.
Also heard as
- rotating assembly
- short block
Related terms
Top-end
The upper components of an engine assembly or the highest RPM range of its powerband.
Short block
A partially assembled engine bottom end lacking the cylinder head and oil pan.
Big end
The larger end of a connecting rod that attaches to the crankshaft.
Conrod
The metal link that connects a piston to the crankshaft in an internal combustion engine.