[Big Dave]

Everything has a natural resonant frequency. You can vary itr with mass or damping (damping usually involve some energy wastage).

You can move the resonant frequency around but you cannot eliminate it.

Engineers find the resonant frequency and do their best to operate the engine at other frequencies. Under the resonant or over it works equally well.

Problem is that the air/exhaust path has its own resonant. This is why some naturally aspirated engines are peaky. Sometimes the engineers use this resonance to increase volumetric efficiency.

Classic example is the Chevy small-block. The mechanical drive line has a resonant around 950 RPM and one learns to blast through that RPM fast as possible. But the air/exhaust gas "pipe organ" resonates around 4800 RPM. Engineers use this to get very high HP (due to high vol eff at the resonant) but also get decent MPG at lower RPMs as the frequency is so far off the air/gas resonant. Lower engine HP demands at low RPM makes the lower vol eff insignificant. But when you need the power, rev her up to the resonant and the small block makes extraordinary power.

Two-stroke chain saw and motorcycle engines do this even more dramatically.

Don't go trying to change the resonant frequency of an engine. You'll just break parts. Engineers generally do know what they're doing, and you do not have the access to data they have.

Find your torsional resonant frequency and stay off of it.