For this ? I was going to start a new Thread, but this all goes together , If you have a Carb that is square [barrels the same size] and it is jetted CORRECT front & rear ,it should not matter power valve or not, The question is, Should the A & B fuel flow be the same on the dyno, I see a lot that have WAY different amounts. seems like if the carb is set up properly they would be the same When I tune a carb I disconnect the rear & tune the front with a wide band & then hook up the rear & tune the rear