Oversize Tappet and Tappet-Guide Set. For use with billet cams. Twelve tappets and 12 appropriately-sized tappet guides; 24 pieces total. Tappet O.D. is 1.499". Typically a billet cam has a lobe wider than the standard tappet diameter. By machining the head to accept the larger diameter steel tappet guide set (not shown) the engine builder can then install these larger diameter tappets. For 6-Cylinder engines only. 24-piece set. Special order only. Delivery about four weeks.