Originally Posted By: aquariuscsm
There was a guy here years ago who kept a worn out engine alive using VR1 SAE60. His had bottom end knock and that oil kept it going until he rebuilt it.
We can probably guess that the engine has worn out bearings and a worn oil pump. However, what we might not know is the actual bearing clearance.
As I quoted above, the larger the clearance, the higher viscosity oil needed. Done properly, there is no metal to metal contact, and therefore very little wear.
It's not unusual for race engines to have clearances beyond "worn out" specifications. However, when set up this way, they generally use high volume oil pumps and high viscosity oils. Note: this type of setup is becoming increasingly uncommon, but it was common in the 1970's. I've seen race engines with 0.004++ inches connecting rod bearing clearance. And, they held up just fine. (that's enough clearance to create knock)