A few elementary calculations reveal how feasible this might be. A typical ICE produces a few hundred horsepower using 4-8 cylinders rotating at a few thousand RPM. 1 HP = 745 watts. Figure out how much energy is released per cylinder on each cycle, and compare that to the energy released in a typical fusion ignition. Also note the cycle time of an ICE rotating at a few thousand RPMs, and compare that to the cycle time of a current state-of-the-art fusion reactor. (Hint: the former is measured in milliseconds, the latter currently in months if not years.)