An LED light engine having a high thermal conductivity substrate (e.g., a metal-clad PCB), a plurality of light-emitting-diode (LED) semiconductor devices mechanically connected to the substrate, an outer dike fixed to the substrate and surrounding at least a portion of the LED devices, and a substantially transparent polymeric encapsulant (e.g., optical-grade silicone) disposed on the plurality of LED devices and restrained by said outer dike. In one embodiment, the light engine includes a reflector (e.g., a generally conic reflector) fixed to the substrate to form the outer dike. In another embodiment, an optical component (e.g., a lens, filter, or the like) is optically coupled to the polymeric encapsulant disposed on the LED devices.