I've heard that prolonged driving at low RPMs (AKA "lugging") can cause head gaskets to blow. Is that true and, if yes, can you provide a lowdown of the causality?
I've thought about this a bit and don't see how lugging a motor could blow a head gasket.
I do see, however, how lugging can do damage to other areas of an engine.
That being said, lugging a motor does not give it good volumetric efficiency due to the low RPM's.
Look at this way. An intake track at high RPM's creates an effect where the mass of the air flowing at a high rate 'overfills' the cylinder with an air fuel charge. The velocity of the airflow compresses the charge a bit and give the cylinder greater volumetric efficiency where you are stuffing more volume (at the current barometric pressure) into the cylinder than if it was just opened up to the atmosphere in non-running state.
This higher volumetric efficiency would create a larger explosion of air fuel with more force to potentially damage the head gasket. Not that it would necessarily, this is just in theory.
So, with less than desirable air fuel charge during lugging I am unable to see how it could, specifically, head gasket damage.