In an aspect of the present disclosure, an internal combustion engine is disclosed. The internal combustion engine has a main combustion chamber, a prechamber, an insert in the prechamber, a fuel valve, and an ignition plug. The main combustion chamber is in fluid communication with the prechamber. The prechamber defines an upper volume and a lower volume about a central plane passing through a midpoint of the prechamber. The fuel valve is disposed in the upper volume and is configured to introduce charge into the prechamber. The ignition plug is configured to ignite the charge. The insert is disposed at least partially in the upper volume of the prechamber to promote mixing of the charge.