Any process that activates or increases the frequency, rate or extent of the chemical reactions and pathways involving pyrimidine nucleobases.
Synonyms:
exact_synonym:
positive regulation of pyrimidine base metabolic process; positive regulation of pyrimidine base metabolism; up regulation of pyrimidine base metabolic process; upregulation of pyrimidine base metabolic process
narrow_synonym:
activation of pyrimidine base metabolic process; stimulation of pyrimidine base metabolic process