Assemblies for engines

A pre-combustion chamber assembly for a spark ignition engine, the assembly comprising:

• an ignition chamber adapted to contain at least one electrode of a spark generator;
• and
• the ignition chamber being adapted to communicate with a main engine combustion chamber via a plurality of pre-chamber ports;
• wherein the ignition chamber communicates for removal therefrom of exhaust gas residuals to a distinct storage chamber via at least one transfer port,
• wherein the ignition chamber includes a single substantially cylindrical entrance channel extending directly from said pre-chamber ports in a direction towards an ignition region of the ignition chamber, the ignition region having a larger cross-section than the entrance channel, and
• wherein the entrance channel and the ignition region are joined by a flaring chamber connector wall extending outwardly from the entrance channel to the ignition region.