get a 3/8 in tap.. from the valve side,, tap the 3/8 inch tap into the valve guide,, run it in a least 3/4 inch more the better..( this is to remove the valve guide ) remove the tap. get a 3/8 bolt run it in all the way ( a 3/8 inch x 1 inch will be fine ) now from the valve cover side get a punch just slightly smaller than 3/8 inch.. put the punch into the valve guide and witha 5 pound hammer ( just better ti use , than a regular hammer ) strick the punch,, hard,, after a few hits the valve guide will be removed.. nice thing about this way of doing it.. you are driving the valve guide out from the inside,, this way you will not damage the aluiumn head itself