[quote=belvedere383]I am thinking that there is too little vacuum at idle and it is allowing the PV to open while idling,


Power valve can be open when engine is idleing, power valve adds fuel to the main circuit under heavy load, or takes away fuel away from main circuit at light loads, nothing to do with the idle circuit. Now if the power valve is "blown" or the diaphragm is torn it will let fuel from the bowl straight through to the intake plenum. Engine will be filthy rich and chug and plugs will be wet or very sooty. I believe all new carbs have a check valve to protect PV from backfires.

Your carb possibly needs larger IFR or smaller idle air bleed, or even simple as balancing the throttle blades. If you had to adjust idle speed screw, any where near two turns to attempt to gain idle and did it on the front idle screw only, it may be on transfer circuit on the primary. If this is a possibility take carb off and set throttle blades to see .030 of transfer slot and reinstall. Then adjust front and rear idle speed screws evenly to set desired idle speed. Another possibility is if someone had carb apart to say put jet extensions in, or to change jets, remove power valves etc., it is easy to mix up and use a two circuit metering block gasket on a three circuit carb.