extends from its upper end partially through housing 30 conical surface 64 at the base of concentric bore 42 is formed upon completion of the drilling operation a plurality of axial tubular passages 46 extend upward from the base of upper housing 30 past the lower terminus of central cylindrical bore 42 each lower tubular passage 46 communicates with cylindrical bore 42 thus permitting flow along the entire length of upper housing 30 as seen in fig8 four tubular passages are employed in this embodiment of the invention although a different number of passages could be employed without departing from the spirit of this invention a small conical surface 48 is formed along the lower portion of upper housing 30 and is centrally located communicating with bore 42 this cylindrical conical surface is centrally positioned with respect to upperly extending tubular passages 46 the main body 52 of valve 16 engages upper housing 30 by means of threaded connections 56 located on the exterior of housing 30 and the interior of main body 52 main body 52 comprises an upperly extending cylindrical sleeve 54 at its uppermost end with threaded connections 56 being located on the interior of upper sleeve 54 main body 52 comprises a generally cylindrical member having a cylindrical bore extending completely therethrough this cylindrical bore has an inner diameter larger than the inner diameter of central fluid passageway 42 when main body member 52 is threadably engaged with upper housing 30 an enlarged internal cavity is formed in body member 52 a plurality of longitudinal ribs 58 extend from the outer sleeve of main body 52 into the bore extending through main body 52 each rib terminates in a generally concave surface.