[me and my metro]

I know that back in the 70s we had a small block Chevy come apart at the track. The driver said that when the oil light came on the car gained about 50 hp. This was his guess, we ran Kendall 50 wt racing oil and turned the engine 8300 rpm. He shut it off but the engine was already junk.
If you want to check actual load you will need to use a distributor housing so the complete oil system gets pressure. I assume you are working on a Chevy. The distributor housing completes the oil passages to the lifters. We always primed our new engines back when they had distributor driven oil pumps.