The paper presents the results of SiC nanocrystal characterization using photoluminescence spectroscopy technique. Earlier it was shown that original SiC wafers and porous SiC (PSiC) layers have been characterized by 6H-SiC crystal type with inclusions of 4H-, 15R- and 2H- SiC polytypes. The study of photoluminescence in PSiC layers with different nanocrystal (NC) sizes reveals the intensity stimulation for exciton-related PL bands in NCs of different SiC polytypes. The intensity enhancement for exciton-related PL bands is attributed to the exciton recombination rate increasing due to the realization of exciton weak confinement and exciton-polariton coupling in SiC NCs. The numerical simulation has been done for the dependence of exciton recombination rate versus SiC NC sizes at the assumption of exciton-polariton coupling model.