Don’t forget the engine blocks are must lighter than in the 50s and 60s. Then again, with the lighter mass blocks, the less overhead available to absorb heat if your cooling system malfunctions. Be it a busted hose, gunked up oil, or low water levels, today’s engine blocks aren’t nearly as forgiving in the event of coolant malfunction. Good way to crack a block, bend a camshaft or throw a rod, disrupt a harmonic balancer or transmit some horrible vibration through the tranny.
All these things compound the damage done by a faulty cooling system.
Now, in the event of a faulty lubrication system, things are even worse since engines are designed to operate with higher lubricant pressures and thinner lubricant and less lube in the oil pan. With a higher oil pressure, the bearing areas are reduced to minimize rotating and reciprocating mass and friction losses. Take away the oil pressure and things really go to sh1t fast.
Gone are the days when an engine run out of oil would simply seize up, then free up once cooled off and be good to go simply by pouring some oil into the crankcase.
It used to be that a motor might have some knocking or ticking or sounds or wear and a careful owner could milk quite a few more years of use out of it. Nowdays, once you start to hear a little bit of valvetrain noise, the motor is very near it’s final days.