Fred is right, ring manfacturers recomend driving the vehicle immediately ,putting a load on the engine.I am no pro engine builder,but the several car/truck engines and many motor cycle engines I rebuilt, never smoked using the above technique, and using regular motor oil for the break in.The 261 I did a few years ago,has moly faced rings, the advantage of moly is supposed to be a fast break in and good ring seal.This engine never smoked even when first started.I always use umbrella seals on my 235/261 engines, the exact same ones used for replacements on small block V-8 Chevys.Your problem my be seals however if you are using only the o ring type.
