New engine question

Ok this is probably a stupid question but I have ocd and I cant quit thinking and obsessing about it. I have a new 360 fresh rebuilt I haven't started it or broke it in yet. It's basically a mild stock rebuild factory heads kb pistons factory intake and manifolds. Anywho last night I was turning it over by hand while priming the oil to get back to TDC to install my dissy and I noticed an air escaping psssst noise. Sounded like it was from the rear of the engine at first i thought it was just the air being pushed out the exhaust manifolds but the more I think about it the more I worry its air passing the rings! I'm i worring for nothing? What could it be? I thought about doing a compression test just to make sure I didn't screw up the rings but I really don't want to be cranking the engine over before its broken in. Thanks guys