Re: Volvo MD 2B
The flywheel definitely helps with vibrations but it is still pretty noticeable.
If the headgasket is bad, there may be other problems related to that. Depending on how it blows, you get mixing of many different things. In a worst case, you could have coolant in your cylinder which could cause rust and potentially require major work. Also, you often end up with coolant in your oil which can be bad if it goes unnoticed.
And then there is the question of why the head gasket blew. It is possible that it deteriorated with age and cycles but that is a pretty uncommon problem as far as I know on these engines. It is likely that the gasket was weakened or the cylinder pressure got too high. The gasket could be weakened if the engine was running really hot. To get really high cylinder pressure on a naturally aspirated engine, you need a problem like improper timing or injection problems.
If it were me, I would want to get to the bottom of the head gasket issue and try to establish why it happened.