Damage your engine?? How could that be? All the expasion chamber does is produce a positive and negative wave cycle to compress the bypass fuel back into the cylinder than help in evacuating the exhaust fumes

If this is missing then all that happens is you might get blow by of fuel, which can be compensated by running rich.

The only thing I would expect is that the engine will produce a slightly less power and peak at a lower RPM and use slightly more fuel.