The heat of combustion of ethanol into carbon dioxides and water is $-327$ Kcal at constant pressure. The heat evolved (in cal) at constant volume at $27° \mathrm{C}$ (if all gases behave ideally) is $\left(\mathrm{R}=2 {\mathrm{calmol}}^{-1}{\mathrm{K}}^{-1}\right)$________