Here we used AlCl3 to transform tetrahydrotricyclopentadiene (THTCPD) into a high-energy-density liquid fuel. The reactant contains three inseparable isomers (I, II, and III). Quantum computation shows the possibility of endo fragments of THTCPD turning into exo counterparts. However, experiment indicates the isomerization only happens on norbornyl fragment,, but cyclopropyl fragments remain unchanged. Reactants I and II containing both norbornyl and cyclopropyl fragments are slowly isomerized, and the reactions are reversible, whereas III without a cyclopropyl fragment is converted quickly. The effects of the reaction conditions were studied. A 5% concentration of AlCl3 shows enough catalytic activity. A temperature higher than 15 degrees C is not preferred because it lowers the equilibrium conversion. A halohydrocarbon solvent such as 1,2-dichloroethane is necessary. Pseudo-first-order reversible kinetics was established for the isomerization of I and H. The heat of reaction is 22.94 and 17.69 kJ/mol, respectively. The resulting mixture shows good potential for advanced propulsion due to its high energy content and low freezing point.