I have run as low as .028 in a SB with no contact. That being said, it's gonna depend on bore size, and bore clearance, bearing clearance, rod material and RPM. Also remember on an aluminum block the clearance with steel rods will grow as it warms up, aluminum rods should grow at a similar rate and keep clearance about the same.

I am not causing global warming, I am just trying to hold off a impending Ice Age!