A rotary engine side housing is provided that includes a side plate portion, a side housing body portion, a coolant chamber, and a plurality of posts. The side plate portion has exterior and interior surfaces. The coolant chamber is disposed internally within the side housing body portion. The coolant chamber is defined by a chamber base surface, the peripheral side walls, and the side plate portion interior surface. The chamber base surface and the side plate portion interior surface are spaced apart from one another and the one or more peripheral side walls extend there between. The plurality of posts extend between the chamber base surface and the side plate portion interior surface. The side plate portion, the side body housing portion, and the plurality of posts are integrally formed with one another.