[Binx]

Putting the load on a newly rebuilt engine as well as varying the "on" and "off" throttle is to get the rings to seat properly. A hard throttle builds pressure inside the ring grooves to force the rings out to the cylinders as well as mating the ring to the piston's ring land. Off throttle draws a hard vacuum and pulls oil up the cylinder wall (as much as oil control rings will allow) to cool and disperse metal shavings and carbon particles as the rings literally scrape the the rough surface of a honed cylinder and lap themselves. I don't doubt what charlie ny says about high tension rings - especially iron. They'll seat to the walls quickly but only a healthy on-and-off load will get them to seat to the ring lands.

Lonnie