when you use a plate it raises the jug up making the squish head clearance ~more ~correct .it gets the tops of the ports similar ot stock(which still is a mile off) but now the piston drops down i nthe hole significantly lower and al l the gases are bascily hitting up against a cylinder wall instead of being drawn in pumped efficeintly through the engine.reshaping/altering the ports ot match the new stroke is the only way it wil lever be right and make the most benefit.just slapping a spacer plate under it and calling it a day will only add a few ponies and youll be disappointed