Siamesed

Arrangement of ports when intake or exhaust valves are in pairs which allows two-into-one passages to be cast into the cylinder head. For example, with the usual valve arrangement in a four-cylinder engine the head can be designed so only two ports connect to the intake manifold and only three to the exhaust manifold. Also, when the engine cylinders are connected solidly together (as in the Vega block) instead of being totally surrounded by water jackets, the cylinders are said to be siamesed.