Converting existing aviation internal combustion engines to run on hydrogen could be a way to make aviation more sustainable. This work is in preparation to actual engine tests, and the goal is therefore to investigate the potential challenges of such a conversion and to assess where the opportunities lie in terms of performance optimization. This is done using a CFD model of an internal combustion engine in ANSYS Forte. Using this model, a form of optimized hydrogen injection is found that increases the power output, while decreasing the NOx emissions. Safe engine operation during testing can be ensured by monitoring the pressure inside the combustion chamber and starting off with low equivalence ratios and retarded spark timings. Further recommendations are made, such as installing injectors in the combustion chamber to facilitate direct injection and replacing the spark plugs for cold-rated ones.