currently running a summitt 750 carb on my 330 cu inch y block, sitting in a rolling chassis while I work on rest of vehicle.  If I don't get to start and run for .about a week, the float bowls drain completely to where I have to manually fill the float bowls.  I've worked out a simple way to do that, but my question is where is all that gas going?  Hard to believe it is ALL evaporating, but suppose its possible. running fuel out of  5 gal tank sitting on the garage floor, and line has a fuel filter.   flowing back into the 5 gal tank? Concerned it may be migrating into oil pan.  Would it hurt the motor to just let engine run out of gas as a way to eliminate this "drainback"?  Engine is equipped with a Masterlube Pre'oiling system.