however valve needle seat 40 also includes an arcuate circular annular groove 92 having an arcuate surface 94 as shown which connects the vertical surface and the horizontal surface of the groove 92 as shown the function and purpose of groove 92 will best be appreciated by referring to fig9 which illustrates a plan view of lower valve needle guide 80 referring now to fig9 lower valve needle guide 80 includes arcuate apertures 96 which permit the flow of gaseous fuel therethrough for passage through valve aperture 41 although arcuate apertures 96 are relatively large the lower valve needle guide nevertheless tends to present a restriction to the passage of gaseous fuel thereby accordingly in the structure shown in fig7 as the needle 16 moves downwardly toward the valve seat 82 to pinch the flow at the contact points 43 immediately prior to actual contact the pressure differential across the contact points 43 is substantial in that the pressure between the lower valve guide and the contact points 43 is substantially greater than the pressure on the opposite side of the contact points 43 just prior to contact being completed in fact the presence of the lower needle guide 80 tends to increase the pressure in the zone immediately above the contact.