166 the balance piston 176 is hollow and open at an upper end in the closed position of the valve 160 an annular upper edge of the piston 176 engages a lip seal 178 which prevents gas transfer between the intake and exhaust systems through the valve when the valve is closed the lip seal 178 is carried by a floating shaft seal 179 having a flange 180 which is urged downwardly against a sealing surface 181 as before by a wave spring 102 seated against a gas shield 182 a floating actuator seal 183 is seated on the shaft seal 179 and surrounds the shaft upper portion 124 to limit the passage of gases up into the solenoid actuator 106 vents 184 185 are provided above and below the gas shield 182 to minimize gas transmission between the valve body or seat tube 166 and the solenoid actuator 106 egr valve 162 shown in fig6 is generally similar to valve 160 but the valve assembly 186 differs in details of the seat tube 187 which carries a radial piston seal 188 that engages an outer surface of the balance piston 176 when the valve is closed the radial piston seal 188 is also engaged by the lower edge of a modified floating shaft seal 190 which is urged downwardly by the wave spring 102 as before the construction is otherwise similar to that of valve 160 egr valve 164 shown in fig7 is again similar to valves.