One advantage to building and possibly stroking a 273 is the small bore diameter is going to aid detonation resistance due to the reduced flame travel. Enhancing swirl will also benefit detonation resistance. Widen the intake port on the cylinder wall side. Use a sonic thickness measurement tool to make sure you do not find a water well. The top of the port should be raised mainly on the cylinder wall side. This will aid swirl which relates to quicker burn before detonation threshold is reached.
