Well, because the low pressure safety valve is in the distribution block, if you don't hold it from switching, its far harder if not impossible to clear out ALL the air. I don't have a vacuum bleeder, and gravity bleeding is not complete...
'68 400HO Coupe, 4 spd, 259 interior, Windward Blue. My other car's a Johnson 15 outboard on a '61 Starcraft rowboat... Just sayin'.
