To be honest there pretty reliable and well designed/built. The weak point is the connecting rods and I have rebuilt a couple that have slightly bent rods due to increased boost (been chipped). When this happens the small end catches on the crank web resulting in a bottom end knock.

Rear main failures were fairly common on the early engines but we don’t get too many failing now.

Thermostats can sometimes stick and cause overheating and if not noticed in time will lead to head gasket failure.

Very rarely the aluminium castings can go pourus and lead to an oil leak.