Decreasing conventional oil reserves and existence of large heavy oil and bitumen reservoirs demand novel and cost-effective production and upgrading schemes. One three sequential steps "visbreaking-adsorption-catalytic steam gasification" upgrading process was recently introduced by the group. Thermal cracked heavy molecules were shown to be key components for improved adsorption over solid sorbents. Characterization of the feedstock and the visbroken products is an important part of the study. In this paper, high temperature simulated distillation (HTSD) characterization is covered. Bimodal and monomodal HTSD chromatographic distributions were observed depending on sample relative abundance of heavy resins and asphaltenes. These polar compounds are responsible for the high temperature chromatographic mode. Secondary "on-column" cracking of heavy petroleum components was observed, however not contributing dramatically to the relative abundance of the chromatographic modes. Changes brought by thermal cracking reactions were observed to change detector responses for asphaltene compounds. It seems that this aspect is related to heteroatomic species affecting the burning properties of asphaltene samples. The abundance of the high temperature chromatographic mode was proposed as a feasible crackability ("visbreakability") index for bimodal petroleum samples. Also, preliminary findings suggest that the HTSD FID response within the second chromatographic mode can be a general indicator of sample thermal maturity, either induced or geothermal.