A fluid flow control valve (10, 110) including: a valve body (12, 112) having an inlet port, an outlet port in selective fluid communication with the inlet port by a main passageway through the valve body (12, 112), and a valve seat (56, 156) surrounding the main passageway; a valve member (58, 158) mounted in the valve body (12, 112) for axial movement between closed and open positions respectively blocking and permitting flow through the valve seat (56, 156), the valve member (58, 158) having a piston portion (60, 160) made of a plastic material and a pilot orifice through the piston portion (60, 160), in which the piston portion (60, 160) separates a control chamber (62, 162) upstream of the pilot orifice from a point downstream of the valve seat (56, 156), and in which the pilot orifice is for bleeding off pressure from the control chamber (62, 162) to the point downstream of the valve seat (56, 156); a plunger (32, 132) movable between a closed position blocking flow through the pilot orifice and an open position allowing flow through the pilot orifice; axially spaced apart spring energized wiper seals (70, 72) that radially support the piston (60, 160) within the passageway while allowing limited radial movement within the passageway; and a bleed orifice in communication with the inlet and the control chamber (62, 162) for allowing pressure from the inlet to build up in the control chamber (62, 162) for urging the valve member (58, 158) toward the closed position when the plunger (32, 132) is in the closed position, characterised in that the bleed and pilot orifices (64, 66) are machined into steel inserts (80, 82) secured in the plastic material of the piston (60, 160). a valve body (12, 112) having an inlet port, an outlet port in selective fluid communication with the inlet port by a main passageway through the valve body (12, 112), and a valve seat (56, 156) surrounding the main passageway; a valve member (58, 158) mounted in the valve body (12, 112) for axial movement between closed and open positions respectively blocking and permitting flow through the valve seat (56, 156), the valve member (58, 158) having a piston portion (60, 160) made of a plastic material and a pilot orifice through the piston portion (60, 160), in which the piston portion (60, 160) separates a control chamber (62, 162) upstream of the pilot orifice from a point downstream of the valve seat (56, 156), and in which the pilot orifice is for bleeding off pressure from the control chamber (62, 162) to the point downstream of the valve seat (56, 156); a plunger (32, 132) movable between a closed position blocking flow through the pilot orifice and an open position allowing flow through the pilot orifice; axially spaced apart spring energized wiper seals (70, 72) that radially support the piston (60, 160) within the passageway while allowing limited radial movement within the passageway; and a bleed orifice in communication with the inlet and the control chamber (62, 162) for allowing pressure from the inlet to build up in the control chamber (62, 162) for urging the valve member (58, 158) toward the closed position when the plunger (32, 132) is in the closed position, characterised in that the bleed and pilot orifices (64, 66) are machined into steel inserts (80, 82) secured in the plastic material of the piston (60, 160).