Imo i say 10/30 too heavy an oil robs power.Newly built 493 stroker, about 1 hour running on test stand….
Next oil change-
Lucas High Zinc hot rod 10w-40, or 20w-50?
Engine masters did a show on oil viscosity and found no difference in power from zero weight to 50 weight oil, so run the thickest oil you can get away with in your climate.Imo i say 10/30 too heavy an oil robs power.